Chemistry Blog

Fusion Weapons

2007-05-02T08:33:00.000+05:45

Fission weapons discussed above are ultimately limited in their destructive capability by the sheer size a subcritical mass can assume -- and be imploded quickly enough by high explosives to form a supercritical assembly. The largest known pure fission weapon tested had a 500 kiloton yield. This is some thirty-eight times the release which destroyed Hiroshima in 1945. Not satisfied that this was powerful enough, designers developed thermonuclear (fusion) weapons.

Fusion exploits the energy released in the fusing of two atoms to form a new element; e.g. deuterium atoms fusing to form helium, ²H + ²H = ⁴He₂ , as occurs on the sun. For atoms to fuse, very high temperatures and pressures are required. Only fusion of the lightest element, hydrogen, has proven practical. And only the heavy isotopes of hydrogen, ²H (deuterium) and ³H (tritium), have a low enough threshold for fusion to have been used in weapons successfully thus far.

The first method tried (boosting) involved simply placing ³H in a void within the center of a fission weapon, where tremendous temperatures and high pressures were attendant to the fission explosion. This worked; contributing energy to the overall explosion, and boosting the efficiency of the Pu fissioning as well (fusion reactions also release neutrons, but with much higher energy).

Because ³H is a gas at room temperature, it can be easily 'bled' into the central cavity from a storage bottle prior to an explosion, and impact the final yield of the device. This is still used today, and allows for what is termed 'dial-a-yield' capability on many stockpiled weapons.

Multistage thermonuclear weapons -- the main component of today's strategic nuclear forces -- are more complex. These employ a 'primary' fission weapon to serve merely as a trigger. As mentioned above, the fission weapon is characterized by a tremendous energy release in a small space over a short period of time. As a result, a very large fraction of the initial energy release is in the form of thermal X-rays.

These X-rays are channeled to a 'secondary' fusion package. The X-rays travel into a cavity within a cylindrical radiation container.

The radiation pressure from these X-rays either directly, or through an intermediate material often cited as a polystyrene foam, ablates a cylindrical enclosure containing thermonuclear fuel (shown in blue at left); this can be Li²H (lithium deuteride).

Running along the central axis of this fuel is a rod of fissile material, termed a 'sparkplug'.

The contracting fuel package becomes denser, the sparkplug begins to fission, neutrons from this transmute the Li²H into ³H that can readily fuse with ²H (the fusion reaction ³H + ²H has a very high cross-section, or probability, in typical secondary designs), heat increases greatly, and fusion continues through the fuel mass.

A final 'tertiary' stage can be added to this in the form of an exterior blanket of ²³⁸U, wrapping the outer surface of the radiation case or the fuel package. ²³⁸U is not fissionable by the slower neutrons which dominate the fission weapon environment, but fusion releases copious high energy neutrons and this can fast fission the ordinary uranium.

This is a cheap (and radiologically very dirty) way to greatly increase yield. The largest weapon ever detonated -- the Soviet Union's 'super bomb', was some 60 MT in yield, and would have been nearer 100MT had this technique been used in its tertiary. Again, to control the yield precisely, ³H may be bled from a separate tank into the core of the primary, as shown in the hypothetical diagram on the left of a modern thermonuclear weapon.

This primary/secondary/tertiary or multistage arrangement can be increased -- unlike the fission weapon -- to provide insane governments with any arbitrarily large yield.

Fusion, or thermonuclear weapons, are not simple to design nor are they likely targets of construction for would-be terrorists today.

Many aspects of the relevant radiation transport, X-ray opacities, and ultra-high T and D equations-of-state (EOS) for relevant materials are still classified to this day (though increasing dissemination of weapons-adaptable information from the inertially-confined fusion (ICF) area may change this in time). Keeping such information classified makes good sense.

Source: Simpelthiniking.com

Nuclear Weapons - Fission Wreapons

2007-04-23T18:35:00.000+05:45

Nuclear weapons exploit two principle physical, or more specifically nuclear, properties of certain substances: fission and fusion.

Fission is possible in a number of heavy elements, but in weapons it is principally confined to what is termed slow neutron fission in just two particular isotopes: ²³⁵U and ²³⁹Pu. These are termed fissile, and are the source of energy in atomic weapons. An explosive chain reaction can be started with relatively slight energy input (so-called slow neutrons) in such material.

Isotopes are 'varieties' of an element which differ only in their number of neutrons. For example, hydrogen exists as¹H ²H and ³H -- different isotopes of the same chemical element, with no, one, and two neutrons respectively. All the chemical properties, and most of the physical properties, are the same between isotopes. Nuclear properties may differ significantly, however.

The fission, or 'splitting' of an atom, releases a very large amount of energy per unit volume -- but a single atom is very small indeed. The key to an uncontrolled or explosive release of this energy in a mass of fissile material large enough to constitute a weapon is the establishment of a chain reaction with a short time period and high growth rate. This is surprisingly easy to do.

Fission of ²³⁵U (uranium) or ²³⁹Pu (plutonium) starts in most weapons with an incident source of neutrons. These strike atoms of the fissile material, which (in most cases) fissions, and each atom in so doing releases, on average, somewhat more than 2 neutrons. These then strike other atoms in the mass of material, and so on.

If the mass is too small, or has too large a surface area, too many neutrons escape and a chain reaction is not possible; such a mass is termed subcritical. If the neutrons generated exactly equal the number consumed in subsequent fissions, the mass is said to be critical. If the mass is in excess of this, it is termed supercritical.

Fission (atomic) weapons are simply based on assembling a supercritical mass of fissile material quickly enough to counter disassembly forces.

The majority of the energy release is nearly instantaneous, the mean time from neutron release to fission can be of the order of 10 nanoseconds, and the chain reaction builds exponentially. The result is that greater than 99% of the very considerable energy released in an atomic explosion is generated in the last few (typically 4-5) generations of fission -- less than a tenth of a millisecond.

This tremendous energy release in a small space over fantastically short periods of time creates some unusual phenomena -- physical conditions that have no equal on earth, no matter how much TNT is stacked up.

Plutonium (²³⁹Pu) is the principal fissile material used in today's nuclear weapons. The actual amount of this fissile material required for a nuclear weapon is shockingly small.

In the Fat Man (Nagasaki) weapon design an excess of Pu was provided. Most of the remaining bulk of the weapon was comprised of two concentric shells of high explosives. Each of these was carefully fashioned from two types of explosives with differing burn rates. These, when detonated symmetrically on the outermost layer, caused an implosion or inward-moving explosion.

The two explosive types were shaped to create a roughly spherical convergent shockwave which, when it reached the Pu 'pit' in the center of the device, caused it to collapse.

The Pu pit became denser, underwent a phase change, and became supercritical.

A small neutron source, the initiator, placed in the very center of this Pu pit, provided an initial burst of neutrons -- final generations of which, less than a microsecond later, saw the destruction of an entire city and more than 30,000 people..

Nearly all the design information for weapons such as these is now in the public domain; in fact, considering the fact that fission weapons exploit such a simple and fundamental physical (nuclear) property, it is no surprise that this is so. It is more surprising that so much stayed secret for so long, at least from the general public.

A neutron reflector, often made of beryllium, is placed outside the central pit to reflect neutrons back into the pit. A tamper, often made of depleted uranium or ²³⁸U helps control premature disassembly. Modern fission devices use a technique called 'boosting' , to control and enhance the yield of the device.

Today's nuclear threat lies mostly in preventing this fissile special nuclear material (often referred to as SNM) from falling into the wrong hands: once there, it is a very short step to construct a working weapon.

source : simplethinking

Low-salt diet prevents heart attacks and strokes

2007-04-23T18:09:00.001+05:45

Eating less salt can reduce the risk of cardiovascular disease by 25% and cut the risk of death from all causes by a fifth, according to a new study.

The 15-year study of 2400 people demonstrates for the first time that cutting back on salt can reduce the risk of diseases such as stroke and heart attack, in addition to lowering blood pressure.

Volunteers in the study who were assigned to a low-salt regime had a 20% lower risk of death from all causes over the course of the study than their control counterparts. The findings should compel governments to take more action to reduce the salt content of processed foods, says Nancy Cook at the Brigham and Women's Hospital in Boston, Massachusetts, US, who led the study.

Numerous studies have documented how consuming foods high in salt can lead to high blood pressure. This happens because the salt draws more water into the blood, and the increase in fluid volume exerts more pressure on vessel walls. High blood pressure is known to contribute to heart disease, but few studies have shown a direct link between salty foods and the condition.

Salt snapshot

In the late-1980s and early-1990s Cook and colleagues collected urine samples from more than 3000 people with above-normal blood pressure. Analysing the urine samples collected over the course of a 24-hour-period gave the researchers a snapshot of the subjects' salt intake. On average, they were consuming 10 grams of salt per day.

Cook's team then randomly assigned half of these participants to attend weekly workshops that taught how to cook low-salt meals and read nutrition labels on packaged foods.

After approximately three months of this nutrition counselling, urine sampling revealed that the subjects reduced their daily salt intake by about 3 grams per day on average – the equivalent of about half a teaspoon.

Fifteen years later Cook's team was able to obtain follow-up health information about 2415 of the participants from medical records and telephone interviews.

Healthy choices

Phone interviews indicated that those who had received training on how to reduce their salt intake many years ago continued to consume less of it than their control counterparts. For example, 47% of those who received this intervention said they looked for reduced-salt foods in the supermarket, compared with 29% of the control group.

Of the 200 people who had developed cardiovascular disease – including heart attacks and stroke – in the past 15 years, 112 had received no dietary recommendations and 88 were in the group taught to reduce their salt intake.

After controlling for factors such as weight and age, the researchers calculated that reducing one's salt intake by 30% could decrease the risk of cardiovascular disease by 25%.

Cook says that the results of the study should encourage governments to "work with the food industry to come up with lower sodium foods", and notes that salt content is highest in processed and fast-foods. "People generally consume much more salt than what is biologically needed."

In 2006, the American Medical Association urged the US Food and Drug Administration to revoke the "generally recognised as safe" (GRAS) status of salt and to adopt stricter salt guidelines.

Current US dietary guidelines recommend that people consume less than one teaspoon of salt per day.

Journal reference: BMJ (DOI: 10.1136/bmj.39147.604896.55)

Genes versus heat – a reptile sex trigger

2007-04-23T17:56:00.000+05:45

High temperatures can make an Australian lizard that is genetically male develop into a female. The finding throws new light on how sex is determined in reptiles.

For most reptiles, a gene on a sex chromosome triggers an embryo to develop as either a male or a female. In some species, males have an X and a Y chromosome, while females are XX, as in mammals. In other species of lizards, males are ZZ while females are ZW, as in birds.

But for a third group of reptiles, which includes all crocodiles, alligators and marine turtles, temperature, rather than a gene on a sex chromosome, triggers either male or female differentiation. Extreme low or high temperatures generally lead to more females.

Now a team led by Alex Quinn at Canberra University in Australia has found that the central bearded dragon (Pogona vitticeps) is susceptible to both types of sex trigger, and that temperature can override its genetic gender.

Transitional form

When the team incubated eggs at relatively high temperatures – between 34°C and 37°C – the majority of embryos that had ZZ sex chromosomes (genetically male), hatched as females. The team thinks the bearded dragon represents a transitional form, in evolutionary terms, between the two main methods of sexual determination.

The research shows that, for the bearded dragon at least, the W chromosome is not necessary in producing a female. The team suspects that a double dose of a particular gene on the Z chromosome is instead crucial for maleness, and that this gene is inactivated by high temperatures.

“The possibility that there is a male-determining, dosage-dependent gene on the Z chromosome of bearded dragons is an important insight,” says Quinn, “because to date, scientists have discovered the master sex-determining gene only in mammals and a single species of fish.”

The team plans to hunt for that master gene in the bearded dragon. They also want to investigate how widespread the phenomenon of temperature sex reversal really is in reptiles.

If many other reptiles with sex chromosomes are also susceptible to temperature, this would broaden the number of species that could be vulnerable to climate change.

“The concern is that the current rate of climate warming could be too rapid for these species to adapt to, and this could potentially result in heavily skewed sex ratios, and even population crashes in some cases,” Quinn says.

Journal reference: Science (vol 316, p 411)

Regular aspirin use may protect cancer

2007-04-23T17:35:00.000+05:45

Regular aspirin use may protect more than just your heart - it could also reduce your risk of getting cancer.

Aditya Bardia and colleagues at the Mayo Clinic College of Medicine in Rochester, Minnesota, analysed the cancer history of more than 22,000 post-menopausal women over 12 years. Those who reported taking aspirin regularly at the start of the study were 16 per cent less likely to develop cancer and 13 per cent less likely to die from it during that time. The only lifestyle factor that influenced the results was smoking, which reduced the protective effect slightly.

Bardia says aspirin's anti-inflammatory action is probably responsible, although a similar effect
was not seen with other anti-inflammatories, such as ibuprofen. The findings were presented at a meeting of the American Association for Cancer Research in Los Angeles this week.

From issue 2600 of New Scientist magazine, 23 April 2007, page 16

Fule Cells ?????????

2007-04-07T17:37:00.000+05:45

You’ve probably heard about fuel cells. In 2003, President Bush announced a program called the Hydrogen Fuel Initiative (HFI) during his State of the Union Address. This initiative, supported by legislation in the Energy Policy Act of 2005 (EPACT 2005) and the Advanced Energy Initiative of 2006, aims to develop hydrogen, fuel cell and infrastructure technologies to make fuel-cell vehicles practical and cost-effective by 2020. The United States has dedicated more than one billion dollars to fuel cell research and development so far.

So what exactly is a fuel cell, anyway? Why are governments, private businesses and academic institutions collaborating to develop and produce them? Fuel cells generate electrical power quietly and efficiently, without pollution. Unlike power sources that use fossil fuels, the by-products from an operating fuel cell are heat and water. But how does it do this?

If you want to be technical about it, a fuel cell is an electrochemical energy conversion device. A fuel cell converts the chemicals hydrogen and oxygen into water, and in the process it produces electricity.

The other electrochemical device that we are all familiar with is the battery. A battery has all of its chemicals stored inside, and it converts those chemicals into electricity too. This means that a battery eventually "goes dead" and you either throw it away or recharge it.

With a fuel cell, chemicals constantly flow into the cell so it never goes dead -- as long as there is a flow of chemicals into the cell, the electricity flows out of the cell. Most fuel cells in use today use hydrogen and oxygen as the chemicals.

Sir William Grove invented the first fuel cell in 1839. Grove knew that water could be split into hydrogen and oxygen by sending an electric current through it (a process called electrolysis). He hypothesized that by reversing the procedure you could produce electricity and water. He created a primitive fuel cell and called it a gas voltaic battery. After experimenting with his new invention, Grove proved his hypothesis. Fifty years later, scientists Ludwig Mond and Charles Langer coined the term fuel cell while attempting to build a practical model to produce electricity.

There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by their operating temperature and the type of electrolyte they use. Some types of fuel cells work well for use in stationary power generation plants. Others may be useful for small portable applications or for powering cars. The main types of fuel cells include:

Polymer exchange membrane fuel cell (PEMFC)
The Department of Energy (DOE) is focusing on the PEMFC as the most likely candidate for transportation applications. The PEMFC has a high power density and a relatively low operating temperature (ranging from 60 to 80 degrees Celsius, or 140 to 176 degrees Fahrenheit). The low operating temperature means that it doesn't take very long for the fuel cell to warm up and begin generating electricity.

Solid oxide fuel cell (SOFC)
These fuel cells are best suited for large-scale stationary power generators that could provide electricity for factories or towns. This type of fuel cell operates at very high temperatures (between 700 and 1,000 degrees Celsius). This high temperature makes reliability a problem, because parts of the fuel cell can break down after cycling on and off repeatedly. However, solid oxide fuel cells are very stable when in continuous use. In fact, the SOFC has demonstrated the longest operating life of any fuel cell under certain operating conditions. The high temperature also has an advantage: the steam produced by the fuel cell can be channeled into turbines to generate more electricity. This process is called co-generation of heat and power (CHP) and it improves the overall efficiency of the system.

Alkaline fuel cell (AFC)
This is one of the oldest designs for fuel cells; the United States space program has used them since the 1960s. The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized.

Molten-carbonate fuel cell (MCFC)
Like the SOFC, these fuel cells are also best suited for large stationary power generators. They operate at 600 degrees Celsius, so they can generate steam that can be used to generate more power. They have a lower operating temperature than solid oxide fuel cells, which means they don't need such exotic materials. This makes the design a little less expensive.

Phosphoric-acid fuel cell (PAFC)
The phosphoric-acid fuel cell has potential for use in small stationary power-generation systems. It operates at a higher temperature than polymer exchange membrane fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars.

Direct-methanol fuel cell (DMFC)
Methanol fuel cells are comparable to a PEMFC in regards to operating temperature, but are not as efficient. Also, the DMFC requires a relatively large amount of platinum to act as a catalyst, which makes these fuel cells expensive.

Source : How Stuff Works , Wikipedia

A Hydrogen Fule Cell In Ten Minutes

2007-04-06T10:17:00.000+05:45

A fuel cell is a device that converts a fuel such as hydrogen, alcohol, gasoline, or methane into electricity directly. A hydrogen fuel cell produces electricity without any pollution, since pure water is the only byproduct.

Hydrogen fuel cells are used in spacecraft and other high-tech applications where a clean, efficient power source is needed.

You can make a hydrogen fuel cell in your kitchen in about 10 minutes, and demonstrate how hydrogen and oxygen can combine to produce clean electrical power.

To make the fuel cell, we need the following:
>One foot of platinum coated nickel wire, or pure platinum wire.
>A popsickle stick or similar small piece of wood or plastic.
>A 9 volt battery clip.
>A 9 volt battery.
>Some transparent sticky tape.
>A glass of water.
>A volt meter.

The first step is to cut the platinum coated wire into two six inch long pieces, and wind each piece into a little coiled spring that will be the electrodes in our fuel cell. Next, we cut the leads of the battery clip in half and strip the insulation off of the cut ends. Then we twist the bare wires onto the ends of the platinum coated electrodes, as shown in the photo. The battery clip will be attached to the electrodes, and two wires will also be attached to the electrodes, and will later be used to connect to the volt meter.

The electrodes are then taped securely to the popsickle stick. Lastly, the popsickle stick is taped securely to the glass of water, so that the electrodes dangle in the water for nearly their entire length. The twisted wire connections must stay out of the water, so only the platinum coated electrodes are in the water.
Now connect the red wire to the positive terminal of the volt meter, and the black wire to the negative (or "common") terminal of the volt meter. The volt meter should read 0 volts at this point, although a tiny amount of voltage may show up, such as 0.01 volts.

Your fuel cell is now complete.

To operate the fuel cell, we need to cause bubbles of hydrogen to cling to one electrode, and bubbles of oxygen to cling to the other. There is a very simple way to do this.

We touch the 9 volt battery to the battery clip (we don't need to actually clip it on, since it will only be needed for a second or two).

Touching the battery to the clip causes the water at the electrodes to split into hydrogen and oxygen, a process called electrolysis. You can see the bubbles form at the electrodes while the battery is attached.

Now we remove the battery. If we were not using platinum coated wire, we would expect to see the volt meter read zero volts again, since there is no battery connected.

The platinum acts as a catalyst, allowing the hydrogen and oxygen to recombine.

The hydrolysis reaction reverses. Instead of putting electricity into the cell to split the water, hydrogen and oxygen combine to make water again, and produce electricity.

We initially get a little over two volts from the fuel cell. As the bubbles pop, dissolve in the water, or get used up by the reaction, the voltage drops, quickly at first, then more slowly.

After a minute or so, the voltage declines much more slowly, as most of the decline is now due only to the gasses being used up in the reaction that produces the electricity.

Notice that we are storing the energy from the 9 volt battery as hydrogen and oxygen bubbles.

We could instead bubble hydrogen and oxygen from some other source over the electrodes, and still get electricity. Or we could produce hydrogen and oxygen during the day from solar power, and store the gasses, then use them in the fuel cell at night. We could also store the gasses in high pressure tanks in an electric car, and generate the electricity the car needs from a fuel cell.

OK the fun part again :

The electrode connected to the negative side of the battery has electrons that are being pushed by the battery. Four of the electrons in that electrode combine with four water molecules. The four water molecules each give up a hydrogen atom, to form two molecules of hydrogen (H2), leaving four negatively charged ions of OH-.

The hydrogen gas bubbles up from the electrode, and the negatively charged migrate away from the negatively charged electrode.

At the other electrode, the positive side of the battery pulls electrons from the water molecules. The water molecules split into positively charged hydrogen atoms (single protons), and oxygen molecules. The oxygen molecules bubble up, and the protons migrate away from the positively charged electrode.

The protons eventually combine with the OH- ions from the negative electrode, and form water molecules again.

When we remove the battery, the hydrogen molecules that are clinging as bubbles to the electrode, break up due to the catalytic action of the platinum, forming positively charged hydrogen ions (H+, or protons), and electrons

At the other electrode, the oxygen molecules stuck in bubbles on the platinum surface draw electrons from the metal, and then combine with the hydrogen ions in the water (from the reaction at the other electrode) to form water.

The oxygen electrode has lost two electrons to each oxygen molecule. The hydrogen electrode has gained two electrons from each hydrogen molecule. The electrons at the hydrogen electrode are attracted to the positively charged oxygen electrode. Electrons travel more easily in metal than in water, so the current flows in the wire, instead of the water. In the wire, the current can do work, such as lighting a bulb, or moving a meter.

source : sci-toys

Make a solar cell in your kitchen

2007-04-03T09:03:00.000+05:45

A solar cell is a device for converting energy from the sun into electricity.The high-efficiency solar cells ,are made from highly processed silicon, and require huge factories, high temperatures, vacuum equipment, and lots of money.

If we are willing to sacrifice efficiency for the ability to make our own solar cells in the kitchen out of materials from the neighborhood hardware store, we can demonstrate a working solar cell in about an hour.

Our solar cell is made from cuprous oxide instead of silicon. Cuprous oxide is one of the first materials known to display the photoelectric effect, in which light causes electricity to flow in a material.

Thinking about how to explain the photoelectric effect is what led Albert Einstein to the Nobel prize for physics, and to the theory of relativity.

Materials you will need:

The solar cell is made from these materials:

>A sheet of copper flashing from the hardware store. We will need about half a square foot.

>Two alligator clip leads.

>Low voltage bulb

>An electric stove. The gas stove wont work . The little 700 watt burners probably won't work -- mine is 1100 watts, so the burner gets red hot.

>A large clear plastic bottle off of which you can cut the top. A large mouth glass jar will also work.

>Table salt. We will want a couple tablespoons of salt.

>Tap water.

>Sand paper or a wire brush on an electric drill.

>Sheet metal shears for cutting the copper sheet.

How to build the solar cell:

The first step is to cut a piece of the copper sheeting that is about the size of the burner on the stove. Wash your hands so they don't have any grease or oil on them. Then wash the copper sheet with soap or cleanser to get any oil or grease off of it. Use the sandpaper or wire brush to thoroughly clean the copper sheeting, so that any sulphide or other light corrosion is removed.

Next, place the cleaned and dried copper sheet on the burner and turn the burner to its highest setting.

As the copper starts to heat up, you will see beautiful oxidation patterns begin to form. Oranges, purples, and reds will cover the copper.

As the copper gets hotter, the colors are replaced with a black coating of cupric oxide. This is not the oxide we want, but it will flake off later, showing the reds, oranges, pinks, and purples of the cuprous oxide layer underneath.

When the burner is glowing red-hot, the sheet of copper will be coated with a black cupric oxide coat. Let it cook for a half an hour, so the black coating will be thick. This is important, since a thick coating will flake off nicely, while a thin coat will stay stuck to the copper.

After the half hour of cooking, turn off the burner. Leave the hot copper on the burner to cool slowly. If you cool it too quickly, the black oxide will stay stuck to the copper.

As the copper cools, it shrinks. The black cupric oxide also shrinks. But they shrink at different rates, which makes the black cupric oxide flake off.

The little black flakes pop off the copper with enough force to make them fly a few inches. This means a little more cleaning effort around the stove, but it is fun to watch.

When the copper has cooled to room temperature (this takes about 20 minutes), most of the black oxide will be gone. A light scrubbing with your hands under running water will remove most of the small bits. Resist the temptation to remove all of the black spots by hard scrubbing or by flexing the soft copper. This might damage the delicate red cuprous oxide layer we need to make to solar cell work.

Cut another sheet of copper about the same size as the first one. Bend both pieces gently, so they will fit into the plastic bottle or jar without touching one another. The cuprous oxide coating that was facing up on the burner is usually the best side to face outwards in the jar, because it has the smoothest, cleanest surface.

Attach the two alligator clip leads, one to the new copper plate, and one to the cuprous oxide coated plate. Connect the lead from the clean copper plate to the positive terminal of the meter. Connect the lead from the cuprous oxide plate to the negative terminal of the meter.

Now mix a couple tablespoons of salt into some hot tap water. Stir the saltwater until all the salt is dissolved. Then carefully pour the saltwater into the jar, being careful not to get the clip leads wet. The saltwater should not completely cover the plates -- you should leave about an inch of plate above the water, so you can move the solar cell around without getting the clip leads wet.

The chemistry behind it :

Cuprous oxide is a type of material called a semiconductor. A semiconductor is in between a conductor, where electricity can flow freely, and an insulator, where electrons are bound tightly to their atoms and do not flow freely.

In a semiconductor, there is a gap, called a bandgap between the electrons that are bound tightly to the atom, and the electrons that are farther from the atom, which can move freely and conduct electricity.

Electrons cannot stay inside the bandgap. An electron cannot gain just a little bit of energy and move away from the atom's nucleus into the bandgap. An electron must gain enough energy to move farther away from the nucleus, outside of the bandgap.

Similarly, an electron outside the bandgap cannot lose a little bit of energy and fall just a little bit closer to the nucleus. It must lose enough energy to fall past the bandgap into the area where electrons are allowed.

When sunlight hits the electrons in the cuprous oxide, some of the electrons gain enough energy from the sunlight to jump past the bandgap and become free to conduct electricity.

The free electrons move into the saltwater, then into the clean copper plate, into the wire, through the meter, and back to the cuprous oxide plate.

*Note:The cell produces 50 microamps at 0.25 volts.
This is 0.0000125 watts (12.5 microwatts).
Don't expect to light light bulbs or charge batteries with this device. It would take acres of them to power your house.

Source : SciToys

Free Beer For Geeks (Free As In Freedom)

2007-03-24T18:39:00.000+05:45

Vores Øl (Danish for Our Beer) is presented as the first open source beer. Today also known as Free Beer. The recipe is published under a Creative Commons license. The beer was created by students at the IT-University in Copenhagen together with Superflex, a Copenhagen-based artist collective, to illustrate how open source concepts might be applied outside the digital world. The students brewed the first 100 litre batch, titled 'version 1.0', of the dark heavy beer in the school cafeteria, and created label designs and a website to promote the beer and publish the recipe.

Recipe

The following recipe is as shown on the official website (As of September 2005), although other variants may exist due to the freedom given to modify the recipe.

Recipe for approximately 85 l (approximately 6% alcohol by volume).

Malt extract

Four types of malted barley are used:
6 kg pilsner malt
4 kg münsner malt
1 kg caramel malt
1 kg lager malt

The malt is crushed and put in 55–60 °C hot water for 1–2 hours.

The mash is filtered and the liquid now contains about 10 kg malt extract.

Taste and sugar

50 g Hallertauer (Northern Brewer) hops
60 g Tettnang hops
300 g guarana beans (Guarana beans can typically be bought at health food stores).
4 kg sugar

The malt extract is brought to a boil in a large pot with Hallertauer NB hops and approximately 70 l (18.5 gal) of water.

After half an hour, the guarana beans and sugar are added.

The mixture simmers for about an hour, the heat is turned off, and the Tettnang hops are added and left to sit for 10 minutes. The mixture is then filtered and cooled in a sealed container.

Fermentation

Yeast is added and the beer is fermented at room temperature for approximately 2 weeks.

When the beer is fully fermented, it is transferred to bottles. First 4 g sugar is added per liter and some yeast from the bottom of the fermentation tanks for priming.

The beer is then left in the bottles at room temperature for 8-10 days for carbonation.

source :
http://www.superflex.net/projects/freebeer/
http://freebeer.org

Molecular Nanobot in Various Uses

2007-03-23T17:34:00.000+05:45

In Japan photo-reactive nanocrystals are being developed for more efficient solar cell production. Rice University is developing methods that use the reactivity of nanoparticles to clean contaminants, especially biological contaminants from water. In agriculture, nano-sensors will be sprinkled on crops or soil to monitor temperature, water, salinity, nitrogen and disease. Robert Freitas is developing an artificial red blood cell able to deliver 236 times more oxygen to tissues than natural red blood cells. Freitas predicts his device will be used to treat anaemia and lung disorders, but also will enhance human performance in sport and warfare. Researchers at the Florida University have created a nanocapsule gel to deliver drugs into the eyes through soft contact lenses.

The importance of nanotechnology to the future of mankind cannot be overstated. Nanotech’s promise is clean industries, cures for disease, nearly unlimited energy supplies, a continuance of Moore’s Law, the end of hunger, and the elmination of aging. Welcome to Molecular Nanobots.

There is so much to explore once you start exploring within nanotechnology - you'll quickly find that the all aspects of the very small - end up being very, very large

source :- http://www.molecularnanobots.com/

Virtual Lab From ChemCollective

2007-03-20T01:15:00.000+05:45

The Virtual Laboratory from the ChemCollective is a new personal favorite. The online version is a java applet, but they now have a downloadable version that will run on any Windows desktop computer. The software allows a student or instructor to simulate many lab activities. Acid base titration, buffer chemistry, limiting reactant stoichiometry and solution equilibria are but a few of the simulations that are possible with this software. There is also an Authoring Program that allows instructors to design their own lab activities and add their own reagents.

If you have java virtual machine installed than download the 1 MBversion or else download the 12 MB version

Download 12 MB With Java Plugin

Download 1 MB (Without JAVA)

Potato Battery

2007-03-16T05:15:00.001+05:45

If you thought that potatoes were only good for eating than you are wrong . Potatoes can also be used as low voltage battey and to prove this i will teach you to light a low voltage bulb with a potato battery .

Things you need : 2 potatoes (obviously) , glavanized zinc nails , copper wire , low voltage bulb

step 1 : Insert the galvanized nail to the ends of each potato .
step 2: Insert the copper wire to the other end of the patato keeping it as far as possible from the nail
step 3: Join the copper wire from the first potato to the nail in second potato so that we have a connection in series
step 4: connect (any device) the bulb to the terminals (the copper terminal act as positive and the zinc act as negative)

The chemistry behind this is simple . The potatoes contain phospheric acid whis allows the electrons to flow from copper to zinc . This means that if you would use fruit like lemons or oranges instead of potatoe the battery would still work . A single potato produces about 0.5 volt of current .

Try experimenting with other low voltage devices or by adding more potatoes for more power
Do not eat the potatoes after using them for batteries .

Artificial Snow

2007-03-16T05:15:00.000+05:45

Once upon a time, making snow was a straightforward craft. One could simply grind up large blocks of ice and spread the pulverized material where desired or use a basic stand-in material such as cellulose powder or bits of paper. Nowadays, with the advent of better materials and machinery--and because the fluffy white stuff fascinates people to no end--there are myriad ways to pull off a big snow job for indoor or outdoor use using machine-made snow or artificial snow.

Machine-made snow has been substantially refined by the ski industry over the years. Snowmaking serves to extend the ski season or can rescue a dry winter, but it also has become important for controlling snow conditions as the number of skiers has increased and the mode of enjoying the slopes has evolved to include tubing, sledding, and snowboarding. Machine snow is also used in labs to learn how to forecast avalanches.

To make snow, water cooled to just above its freezing point is pumped under high pressure through the nozzles of a "snow gun." Compressed air or electric fans are usually used to help atomize the water into fine droplets and to disperse them over a wide area where they hopefully will freeze before they hit the ground. If not, the snow will be too wet. Other ways to make snow include using a combination of water and compressed air that is frozen by liquid nitrogen, a method used primarily for indoor sports centers. Snow also can be made from carbon dioxide.

Critical to snowmaking for skiing is getting the right combination of temperature and humidity--the lower the humidity, the higher the outdoor temperature can be to form snow. With untreated water, an air temperature of about –8 °C (18 °F) is needed. Another important factor is the need to generate sufficient nucleation sites for ice crystals to form. Nucleation sites can be a few water molecules that coalesce alone; calcium, magnesium, or other ions; or an impurity such as a clay particle or organic matter.

When the temperature isn't quite cold enough--above about –5 °C (23 °F)--snowmakers need little helpers in the form of seed materials added to the water to generate nucleation sites. Silver iodide, kaolin, soaps and detergents, and fungi or lichens are among the materials that have been used.

Currently, the most popular additive is Snomax, a freeze-dried protein powder sold by York Snow, Victor, N.Y. Snomax is derived from Pseudomonas syringae, a common bacterium found on grasses, trees, and vegetable crops. In the 1970s, plant pathologists studying the frost sensitivity of corn plants at the University of Wisconsin, Madison, discovered that the bacteria were responsible for initializing ice crystallization [Nature, 262, 282 (1976)].

A newer seeding product taking the market by storm is called Drift, a liquid polyether-substituted trisiloxane produced by Aquatrols in Cherry Hill, N.J. Drift works as a surfactant to decrease the level of hydrogen bonding in water so the water can freeze more quickly, according to the company.

When it comes to artificial snow, ice, or frost, there are more than 100 different materials that can be used, according to Snow Business, a U.K.-based company that supplies ersatz snow for movie sets. Different classes of materials include paper, plastic, starch and cellulose, or foam.

On movie sets, several products generally will be used in combination or with machine-made snow to create the desired effect. Machine snow is usually avoided because it melts and doesn't look flaky when it's falling. Paper, starch, and cellulose are good materials for falling snow. They can be sprinkled down onto a scene and kept aloft by fans blowing air from the edges of the set. A problem with fans, however, is that the noise may interfere with dialogue. During snow scenes there often will be no dialogue, only music, or the dialogue will be dubbed over.

Paper is one of the most versatile materials because it's weatherproof. Starch and cellulose can give the effect of a light dusting of snow or frost on plants and the ground, but they can be slippery to walk on and can generate a sticky mess. Shredded plastic snow is good for small-scale uses in a studio, although it's more expensive. Firefighting foam works well for deep snow and is fast and inexpensive to use, but it can't be walked on.

A favored material is instant mashed potato flakes. From a distance, the flake snow looks pretty real. The drawback: If it starts raining or the ground somehow gets wet, there's mashed potato slush to slog through. Also, in a close-up shot, potato flakes look like potato flakes, and on moist lips they could present a problem--pass the gravy!

One final type of artificial snow is called dryslope. This is a group of wood, metal, or plastic materials, usually laid down as latticework with void spaces, that is used to ski on out of season or in regions where it does not snow. One downside is the hard materials can lead to a greater risk of injury.

A newer type of dryslope that aims to curb injuries is a multilayer polymer composite matting that resembles carpeting. Two products are Snowflex, made by Briton Engineering Developments, Yorkshire, England, and Powderpak, made by an Atlanta-based company with the same name.

Snowflex, for example, has a slippery polybutylene terephthalate fiber surface layer that sits atop a shock-absorbing pad that has a woven backing. Water piped through the layers exits recessed nozzles and mists the surface, which helps reduce friction even further. This new type of dryslope can be laid out like carpet and cut to fit features such as moguls. It has been used indoors and outdoors to make half pipes and short slopes for freestyle (acrobatic) or downhill skiing and snowboarding.

January 19,2004
Volume 82, Number 03
CENEAR 82 03 p. 72
ISSN 0009-2347
STEVE RITTER

Flash Perodic Table

2007-03-16T04:16:00.000+05:45

Bored with the usual looking perodic table . Check out this cool flash version of the perodic table . You can get all sorts of informations on the elemnts on this perodic table .
Give it a try >>>>

Open Cola

2007-03-12T20:53:00.000+05:45

OpenCola is a brand of cola unique in that the instructions for making it are freely available and modifiable. Anybody can make the drink, and anyone can modify and improve on the recipe as long as they, too, license their recipe under the GNU General Public License. The legal grounds for this are dubious however, as recipes are exempted from copyright as they are techniques, not artworks.

Although originally intended as a promotional tool to explain free software/open source software, the drink took on a life of its own and 150,000 cans were sold. The Toronto-based company Opencola founded by Grad Conn, Cory Doctorow and John Henson became better known for the drink than the software it was supposed to promote. Laird Brown, the company's senior strategist, attributes its success to a widespread mistrust of big corporations and the "proprietary nature of almost everything."

Flavouring formula

* 10.0 g food-grade gum arabic
* 3.50 mL orange oil
* 3.00 mL water
* 2.75 mL lime oil
* 1.25 mL cassia oil
* 1.00 mL lemon oil
* 1.00 mL nutmeg oil
* 0.25 mL coriander oil
* 0.25 mL neroli oil
* 0.25 mL lavender oil

Concentrate formula

* 2.36 kg plain granulated white table sugar
* 2.28 L water
* 30.0 mL caramel colour
* 3.50 tsp. 75% phosphoric acid or citric acid
* 2.00 tsp. flavouring formula
* 0.50 tsp. caffeine (optional)

Beverage formula

Mix the concentrate with 5 parts filtered water and force carbonate the beverage, or use a soda fountain that will combine the concentrate with carbonated water at the tap.

Some members of the free software movement have started an Italian OpenCola project, but without any commercial purpose. The only thing the Italian OpenCola and the "official" OpenCola have in common is the name. The Italian version is clear and has never been sold.

recipe for making open cola -> http://www.colawp.com/colas/400/cola467_recipe.html

or download the formula -> http://upload.wikimedia.org/wikipedia/commons/b/bf/OpenCola_soft_drink_recipe.pdf

Why do we assume that other beings must be based on carbon? Why couldn't organisms be based on other substances?

2007-03-06T20:57:00.000+05:45

Aurthor :- Joseph Lazio

[A portion of this entry is based on a lecture by Alain Leger (IAS) at
the SPIE Astronomical Telescopes and Instrumentation 2000 Conference.]

As far as SETI, the search for extraterrestrial intelligence, is
concerned, we do not assume that other being must be based on carbon.
In fact, SETI is a bit of a misnomer. We are searching for
extraterrestrial *technological* intelligences, technological
intelligences capable of broadcasting their existence over
interstellar distances. Whether the technological civilizations is
based on carbon or some other substance is largely irrelevant. (Of
course, one might worry that intelligences based on some substance
other than carbon might have such different perspectives on the
Universe that, even if they broadcast electromagnetic radiation, they
would do so in a fashion that we would never consider.)

However, when one moves to finding life on other bodies in the solar
system or traces of life on extrasolar planets, there is a definite
carbon chauvinism in our thinking. The most commonly mentioned
alternate to carbon (C) is silicon (Si). It has similar chemical
properties as C, lying just below C in the periodic table of the
elements.

Carbon chauvinism has arisen because C is able to form quite
complicated molecules, in part because its atomic structure is such
that C can bond with up to four other elements. Not only can it bond
with up to four other elements, but C can form multiple bonds with
other elements, particularly itself. (Atoms bond by sharing
electrons, when two atoms share more than one electron they have a
multiple bond. For instance, water is formed by an oxygen atom
sharing the two electrons from two hydrogen atoms. In contrast, there
are many C compounds in which a single C atom shares multiple
electrons with other atom.)

A clear indication of the versatility of C is found in interstellar
chemistry. Interstellar chemistry typically occurs on the surface of
microscopic dust grains contained with large clouds of gas between the
stars. The physical conditions are much different than anything on
the surface of a habitable planet. Nonetheless, of the molecules
identified in interstellar space as of 1998, 84 are based on C and 8
are based on Si. Moreover of the eight Si-based compounds, 4 also
include C.

Thus, while there is definitely a C bias in our thinking, there is at
least some evidence from Nature supporting this bias.

Alternative biochemistry

2007-03-06T20:29:00.000+05:45

Alternative biochemistry is the speculative biochemistry of alien life forms that differ radically from those on Earth. It includes biochemistries that use atoms other than carbon to construct primary cellular structures and/or use solvents besides water. Theories about extraterrestrial life based on alternative biochemistries is common in science fiction.

Atoms other than carbon

Scientists have speculated about the pros and cons of using atoms other than carbon to form the molecular structures necessary for life, but no one has proposed a theory employing such atoms to form all the molecular machinery necessary for life. Since humans are carbon-based beings and have never encountered any life that has evolved outside the earth’s environment, excluding the possibility of all other elements may be considered carbon chauvinism.

Silicon biochemistry

The most commonly proposed basis for an alternative biochemical system is the silicon atom, since silicon has many chemical properties similar to carbon and is in the same periodic table group, the carbon group.

But silicon has a number of handicaps as a carbon alternative. Because silicon atoms are much bigger, having a larger mass and atomic radius, they have difficulty forming double or triple covalent bonds, which are important for a biochemical system. Silanes, which are chemical compounds of hydrogen and silicon that are analogous to the alkane hydrocarbons, are highly reactive with water, and long-chain silanes spontaneously decompose. Molecules incorporating polymers of alternating silicon and oxygen atoms instead of direct bonds between silicon, known collectively as silicones, are much more stable. It has been suggested that silicone-based chemicals would be more stable than equivalent hydrocarbons in a sulphuric-acid-rich environment, as is found in some extraterrestrial locations. In general, however, complex long-chain silicone molecules are still more unstable than their carbon counterparts.

Another obstacle is that silicon dioxide (a common ingredient of many sands), the analog of carbon dioxide, is a non-soluble solid at the temperature range where water is liquid, making it difficult for silicon to be introduced into water-based biochemical systems even if the necessary range of biochemical molecules could be constructed out of it.

Finally, of the varieties of molecules identified in the interstellar medium as of 1998, 84 are based on carbon and 8 are based on silicon. Moreover, of those 8 compounds, four also include carbon within them. This suggests a greater variety of complex carbon compounds throughout the cosmos, providing less of a foundation upon which to build silicon-based biologies. The cosmic abundance of carbon to silicon is roughly 10 to 1.

The Earth, as well as other terrestrial planets, is exceptionally silicon-rich and carbon-poor. However, terrestrial life is carbon-based. Rare carbon proved to be much more successful as a life base than abundant silicon.

It is possible, however, that silicon compounds may be biologically useful under certain exotic environmental conditions, either in conjunction with or in a role less directly analogous to carbon. A simple real-world example is the silicate skeletal structure of diatoms. See biogenic silica.

A. G. Cairns-Smith has proposed that the first living organisms to exist were clay minerals - which were probably based on silicon.

Nitrogen and phosphorus biochemistry

Nitrogen and phosphorus also offer possibilities as the basis for biochemical molecules. Like carbon, phosphorus can form long chain molecules on its own, which would potentially allow it to form complex macromolecules if it were not so reactive. However, in combination with nitrogen, it can form much more stable covalent bonds and create a wide range of molecules, including rings.

Earth's atmosphere is approximately 78% nitrogen, but this would probably not be of much use to a phosphorus-nitrogen (P-N) lifeform since molecular nitrogen (N2) is nearly inert and energetically expensive to "fix" due to its triple bond. (On the other hand, certain Earth plants such as legumes can fix nitrogen using symbiotic anaerobic bacteria contained in their root nodules.) A nitrogen dioxide (NO2) or ammonia (NH3) atmosphere would be more useful. Nitrogen also forms a number of oxides, such as nitrogen monoxide, dinitrogen oxide, and dinitrogen tetraoxide, and all would be present in a nitrogen-dioxide-rich atmosphere.

In a nitrogen dioxide atmosphere, P-N plant analogues could absorb nitrogen dioxide from the air and phosphorus from the ground. The nitrogen dioxide would be reduced, with analogues to sugar being produced in the process, and waste oxygen would be released into the atmosphere. Animals based on phosphorus and nitrogen would consume the plants, use atmospheric oxygen to metabolize the sugar analogues, exhaling nitrogen dioxide and depositing phosphorus, or phosphorus-rich material, as solid waste.

In an ammonia atmosphere, P-N plants would absorb ammonia from the air and phosphorus from the ground, then oxidize the ammonia to produce P-N sugars and release hydrogen waste. P-N animals are now the reducers, breathing in hydrogen and converting the P-N sugars to ammonia and phosphorus. This is the opposite pattern of oxidation and reduction from a nitrogen dioxide world, and indeed from the known biochemistry of Earth. It would be analogous to Earth's atmospheric carbon supply being in the form of methane instead of carbon dioxide.

Debate continues, as several aspects of a phosphorus-nitrogen cycle biology would be energy deficient. Also, nitrogen and phosphorus are unlikely to occur in the ratios and quantity required in the real universe. Carbon, being preferentially formed during nuclear fusion, is more abundant and is more likely to end up in a preferred location.

Other exotic biochemical elements

Arsenic, which is chemically similar to phosphorus, while poisonous for most Earth life, is incorporated into the biochemistry of some organisms. Some marine algae incorporate arsenic into complex organic molecules such as arsenosugars and arsenobetaines. Fungi and bacteria can produce volatile methylated arsenic compounds. Both arsenate reduction and arsenite oxidation have been observed in microbes. Additionally, some prokaryotes can use arsenate as a terminal electron acceptor during anaerobic growth and some can utilize arsenite as an electron donor to generate energy.

Chlorine is sometimes proposed as a biological alternative to oxygen, either in carbon-based biologies or hypothetical non-carbon-based ones. But chlorine is much less abundant than oxygen in the universe, and so it is unlikely that a planet will be able to form which has a large enough concentration of chlorine available on its surface to form the basis of a biochemistry. Chlorine will instead likely be bound up in the form of salts and other inert compounds.

Sulfur is also able to form long-chain molecules, but suffers from the same high reactivity problems that phosphorus and silanes do. The biological use of sulfur as an alternative to carbon is purely theoretical, but strains of sulfur-reducing bacteria have been discovered in exotic locations on earth, and also not so exotic locations, such as aging water systems. These bacteria can utilize elemental sulfur instead of oxygen, reducing sulfur to hydrogen sulfide. Examples of this type of metabolism are green sulfur bacteria and purple sulfur bacteria.

Non-water solvents

In addition to carbon compounds, all currently known terrestrial life also requires water as a solvent. It is sometimes assumed that water is the only suitable chemical to fill this role. Some of the properties of water that are important for life processes include a large temperature range over which it is liquid, a high heat capacity useful for temperature regulation, a large heat of vaporization, and the ability to dissolve a wide variety of compounds. There are other chemicals with similar properties that have sometimes been proposed as alternatives.

Ammonia

Ammonia is perhaps the most commonly proposed alternative. Numerous chemical reactions are possible in an ammonia solution, and liquid ammonia has some chemical similarities with water. Ammonia can dissolve most organic molecules at least as well as water does, and in addition it is capable of dissolving many elemental metals. Given this set of chemical properties it has been theorized that ammonia-based life forms might be possible.

However, ammonia does have some problems as a basis for life. The hydrogen bonds between ammonia molecules are weaker than those in water, causing ammonia's heat of vaporization to be half that of water, its surface tension to be three times smaller, and reducing its ability to concentrate non-polar molecules through a hydrophobic effect. For these reasons, science questions how well ammonia could hold prebiotic molecules together in order to allow the emergence of a self-reproducing system. Ammonia is also combustible and oxidizable and could not exist sustainably in a biosphere that oxidizes it. It would, however, be stable in a reducing environment.

A biosphere based on ammonia would likely exist at temperatures or air pressures that are extremely unusual for terrestrial life. Terrestrial life usually exists within the melting point and boiling point of water at normal pressure, between 0°C (273 K) and 100°C (373 K); at normal pressure ammonia's melting and boiling points are between −78°C (195 K) and −33°C (240 K). Such extremely cooled temperatures create problems, as they slow biochemical reactions tremendously and may cause biochemical precipitation out of solution due to high melting points. Ammonia could be a liquid at normal temperatures, but at much higher pressures; for example, at 60 atm, ammonia melts at −77°C (196 K) and boils at 98°C (371 K).

Ammonia and ammonia-water mixtures remain liquid at temperatures far below the freezing point of pure water, so such biochemistries might be well suited to planets and moons orbiting outside the water-based "habitability zone". Such conditions could exist, for example, under the surface of Saturn's largest moon Titan.

Hydrogen Flouride

Hydrogen flouride like water is a polar molecule, and due to its polarity it can dissolve many ionic compounds. It's melting point is -84°C and its boiling point is 19.54°C, the difference between the two is more than 100°C. HF also hydrogen bonds with its neighbor molecules as do water and ammonia. All of these things make HF a candidate to host life on other planets.

Not much research has been done on liquid HF in regards to its ability to dissolve and react with non-polar molecules. It is possible that the biota in an HF ocean could use the flourine as an electron acceptor to photosynthesize energy.

Other solvents

Other solvents sometimes proposed include methanol, hydrogen sulfide and hydrogen chloride. The latter two suffer from a relatively low cosmic abundance of sulfur and chlorine, which tend to be bound up in solid minerals. A mixture of hydrocarbons, such as the methane/ethane seas once believed to exist on the surface of Titan, could act as a solvent over a wide range of temperatures but would lack polarity. Isaac Asimov, the biochemist and science fiction writer, suggested that poly-lipids could form a substitute for proteins in a non-polar solvent such as methane or liquid hydrogen. Other solvents such as formamide might also be suitable as a solvent that would support alternative biochemistry.

source :- wikipedia

Cambridge Scientists Produce Live Video Showing How Carbon Nanotubes Form

2007-03-06T16:01:00.000+05:45

A Cambridge University-led team of scientists have successfully produced live video footage that shows how carbon nanotubes, more than 10,000 times smaller in diameter than a human hair, form.

The video sequences show nanofibres and nanotubes nucleating around miniscule particles of nickel and are already offering greater insight into how these microscopic structures self-assemble. The films can be viewed on the Cambridge University website at:

http://www.admin.cam.ac.uk/news/special/20070301/

In particular, the team discovered that the carbon network is guided into tubular shape by a drastic restructuring of the nickel – the catalyst in the process. They were also able to track and time the deposition of the carbon around the nickel.

Carbon nanotubes are new building blocks enabling engineers to improve and further miniaturise everyday electronic devices like computers or mobile phones. At the moment scientists can grow nanotubes but cannot accurately control their structure.

Being able to do so is vital as it is the very structure of a nanotube that dictates its properties. The nano-scale video observations mean that scientists will be able to better understand the nucleation of nanotubes and are therefore an important step on the route towards application.

The two sequences show action taking place in real time on an astonishingly small scale. The difference in size between a single-walled nanotube and a human hair is close to the difference between the same human hair and the Eiffel Tower. The microscopic scale involved has, in the past, made it difficult to understand the growth process.

The team used X-rays produced at a synchrotron (a type of particle accelerator) and a modified high-resolution transmission electron microscope to observe and film a process called catalytic chemical vapour deposition. This is one of several methods of producing nanotubes, and involves the application of a gas containing carbon (in this case acetylene) to minute crystalline droplets referred to as “catalyst islands” (the nickel).

As the gas is applied carbon sticks to the catalyst islands forming layers of graphite. In conditions appropriate to creating nanofibres, the nickel particle was pushed upwards in a series of peristaltic movements as the carbon continued to deposit on its sides. At several points the nickel formed a cap which almost “popped” out of the forming tube, leaving a layer of graphite behind it. This process is called “bambooing”, because the resultant carbon nanofibre is a cylinder containing several cavities, each one separated by one of these graphite layers, similar in form to bamboo. Throughout the whole process, the nickel remained crystalline rather than liquid.

The team then looked at conditions more appropriate to producing single-walled carbon nanotubes, which involved less acetylene. The catalyst is not squeezed upwards. Instead, a cap of carbon formed on the top of the nickel, and gradually extended from it to form a tubular structure. The catalyst island was squeezed and reshaped by this process and was moulded by the carbon forming around it rather than retaining its original form.

Dr Stephan Hofmann, who led the research, said: “In order to reach the full application potential for nanotubes, we need to be able to accurately control their growth first. As a manifestation of the impressive progress of nanometrology, we are actually now able to watch molecular objects grow. This new video footage shows that the catalyst itself remains crystalline but is constantly changing its shape as the carbon network is formed around it.

“We cannot yet solve the problem of not being able to self-assemble carbon nanotubes with well-defined characteristics, but we have discovered that if we are to do so, we need to be mindful not just of the carbon dynamics but the changing shape of the catalyst as well.”

source :- http://www.cam.ac.uk

Electrochemical Uses Of Carbon

2007-03-05T22:16:00.000+05:45

Carbon is one of the most abundant elements found on earth. It occurs freely in crystalline forms such as diamond and graphite.The diamond crystal is cubic, with the atoms arranged in a tetrahedral configuration. This arrangement of carbon atoms produces a solid that is the hardest known substance. Consequently, it is used as an industrial abrasive. In addition, diamond has a very high refractive index, hence it produces brilliant cut gems. Graphite, on the other hand, is soft, has a hexagonal structure, with the carbon atoms arranged in layer planes. The spacing between the layer planes in graphite is 0.3354 nm (nm = billionth of a meter). This layer structure facilitates easy cleavage along the planes, which makes it desirable as a solid lubricant. There are variations of the graphite structure. When the dimensions of the layer planes are small and the separation between the layer planes becomes large, the carbon is referred to as amorphous carbon (for example, charcoal, coke, and soot). Because of their difference in structures, diamond is an electrical insulator, whereas graphite is a good electrical conductor. The high conductivity of graphite and its good chemical stability are attractive features for its use in electrochemistry.

Read More :- http://electrochem.cwru.edu/ed/encycl/art-c01-carbon.htm

Chemicals And Their Household Equivalents

2007-02-27T17:41:00.000+05:45

Where can an average student with little to no budget find common chemical component for home use? The following table, compiled from an archive of old chemistry textbooks, lists the household equivalents of chemicals which would ordinarily need to be purchased in large quantity from a chemical supply house. While sources such as the "Anarchist's Cookbook" have given amateur chemistry hobbyists a bad name in recent years, there are many legitimate uses for the following chemicals: science fairs, homemade cleaning solvents (for silver and copper), ceramic glazes for potters, etc.

Link to the table:
http://en.wikipedia.org/wiki/Common_chemicals

The Difference Between Sublimation And Evaporation

2007-02-27T17:05:00.000+05:45

Sublimation and evaporation bring material into vapor phase, then what is the difference between two ?

Sublimation: The transition of a substance from the solid phase
directly to the vapor phase, or vice versa, without passing through an
intermediate liquid phase.

Evaporation: The conversion of a liquid (water) into a vapor (a
gaseous state) usually through the application of heat energy during
the hydrologic cycle; the opposite of condensation.

Source:
http://www.groundwater.org/gi/gwglossary.html

Chemistry Timeline

2007-02-25T14:05:00.000+05:45

Early years

Prior to the acceptance of the scientific method in the 1600's and its application to the field of chemistry, it is somewhat controversial to consider many of the people listed below as "chemists" in the modern sense of the world. However, the ideas of certain great thinkers, either for their prescience, or for their wide and long-term acceptance, bears listing here.

c. 3000 BCE: Egyptians formulated the theory of the Ogdoad the “primordial forces”, from which all was formed; these were the elements of chaos, numbered in eight, that existed before the creation of the sun.

c. 1900 BCE: Hermes Trismegistus, a great Egyptian adept king, is thought to have founded of the art of alchemy.

c. 1500 BCE: the world's first chemist ‘Tapputi’ the perfume-maker was mentioned in a cuneiform tablet in Mesopotamia.

c. 450 BCE: Empedocles - assertes that all things are composed of four primal elements: earth, air, fire, and water, whereby two active and opposing forces, love and hate, or affinity and antipathy, act upon these elements, combining and separating them into infinitely varied forms.

c. 440 BCE: Leucippus and Democritus - Proposes idea of the atom, an indivisible particle that all matter is made of. This idea is largely rejected by natural philosophers in favor of the Aristotlean view.

c. 350 BCE: Aristotle - Based on the ideas of Empedocles, proposes idea of a substance as a combination of matter and form. Describes theory of the Five Elements which is largely accepted throughout the western world for over 1000 years. 50 BCE: Lucretius - Publishes De Rerum Natura, a poetic description of the ideas of Atomism.

c. 770: Abu Musa Jabir ibn Hayyan (aka Geber) - Isolation of numerous acids, including hydrochloric acid, nitric acid, citric acid, acetic acid, tartaric acid, and aqua regia.

c. 900: Abū Bakr Muhammad ibn Zakarīya al-Rāzi (aka Rhazes) - Publishes several treatises on alchemy, including some of the earliest descriptions of controlled distillation and extraction methods. He also developed early method for the production of sulfuric acid.

c. 1220: Robert Grosseteste - Publishes several Aristotelian commentaries where he lays out an early framework for the Scientific Method.

c. 1265: Roger Bacon - Publishes Opus Maius, which among other things, proposes an early form of the Scientific Method, and contains results of his experiments with gunpowder.

c. 1310: Pseudo-Geber - Anonymous Spanish alchemist publishes several books that establish the well-held theory that all metals were composed of various proportions of sulfur and mercury.

17th and 18th centuries

1605: Sir Francis Bacon - Publishes The Proficience and Advancement of Learning, which proposes a scheme credited with being the first description of what would later be known as the scientific method.

1605: Michał Sędziwój - Publishes the alchemical treatise A New Light of Alchemy which proposed the existance of the "food of life" within air, much later recognized as oxygen

1637: René Descartes - Publishes Discours de la méthode, which contains an outline of the scientific method.

1648: Johann Baptista van Helmont - Posthumous publication of his book Ortus medicinae which is cited by some as a major transitional work between alchemy and chemistry, and as an important influence on Robert Boyle. The book contains numerous experiments where, among other things, isolated numerous gaseous products from various chemical reactions, and establishes an early version of the Law of conservation of mass when he notes that the dissolution of metals by an acid did not represent their destruction, as such metals could be reproduced.

1661: Robert Boyle - The Sceptical Chymist - Treatise on the disctinction between chemistry and alchemy, contained ideas of atoms, molecules, and of chemical reactions

1662: Robert Boyle - Boyle's Law - first description of the behavior of gases, specifically the relationship between pressure and volume

1754: Joseph Black - isolation of carbon dioxide, which he called "fixed air".

1758: Joseph Black - formulates concept of latent heat to explain the thermochemistry of phase changes.

1773-1774: Carl Wilhelm Scheele and Joseph Priestly - isolation of oxygen, called by Priestly "dephlogisticated air" and Scheele "fire air".

1778: Antoine Lavoisier - Recognized and named oxygen, recognized its importance and role in combustion.

1787: Antoine Lavoisier - Publishes Méthode de nomenclature chimique , the first modern system of chemical nomenclature.

1787: Jacques Charles - Charles's Law - corrolary of Boyle's Law, describes relationship between temperature and volume of a gas.

1789: Antoine Lavoisier - Publishes Traité Élémentaire de Chimie, the first modern chemistry textbook, gave a complete survey of (at that time) modern chemistry, including the first concise definition of the law of conservation of mass, and thus the founding of the discipline of stoichiometry or quantitative chemical analysis.

1797: Joseph Proust - Law of definite proportions states that elements always combine in small, whole number ratios to form compounds.

1800: Alessandro Volta - Devises the first chemical battery, thereby founding the discipline of electrochemistry.

19th century

1802-1805: Joseph Louis Gay-Lussac - collects and discovers several chemical and physical properties of air and of other gases, including experimental proofs of Boyle's and Charles's laws, and of relationships between density and composition of gases. Also discovers that water is composed of two parts hydrogen and one part oxygen (H2O), instead of HO as previously thought.

1803: John Dalton - Dalton's Law describes relationship between pressure and makeup of gases.
1807-1808: Sir Humphry Davy - Use of electrolysis to isolate numerous elements, including potassium, sodium, calcium, strontium, barium, chlorine and the first discovery of aluminum.

1808: John Dalton - Publishes New System of Chemical Philosophy, which contains first modern scientific description of the atomic theory, and clear description of the law of multiple proportions.

1808: Jöns Jakob Berzelius - Published Lärboki Kemien in which he nvented modern chemical symbols and notation, developed concept of relative atomic weight.

1811: Amedeo Avogadro - Avogadro's law - Equal volumes of gases contain equal numbers of particles.

1815: William Prout - Prout's hypothesis proposes that all elements are conglomerations of hydrogen. Later disproven, though the near equivalence of the masses of protons and neutrons can explain the popularity of it.

1825: Michael Faraday - isolates benzene, the first isolated aromatic hydrocarbon.

1825: Friedrich Wöhler and Justus von Liebig - First confirmed discovery and explanation of isomers, earlier named by Berzelius. Working with cyanic acid and fulminic acid, they correctly deduced that isomerism was caused by differing arrangements of atoms.

1828: Friedrich Wöhler - Synthesized urea, thereby establishing that organic compounds could be produced from inorganic starting materials, disproving the theory of vitalism.

1832: Friedrich Wöhler and Justus von Liebig - Discovery and explanation of functional groups and of radicals in organic chemistry.

1840: Germain Hess - Hess's Law, an early statement of the Law of conservation of energy establishes that energy changes in a chemical process depend only on the states of the starting and product materials and not on the specific pathway taken between the two states.

1847: Hermann Kolbe - Obtains acetic acid from completely inorganic sources.

1848: Lord Kelvin - Establishes concept of absolute zero, the temperature at which all molecular motion ceases.

1849: Louis Pasteur - Discovers chirality and in tartaric acid, starting the study of stereochemistry.

1852: August Beer - Beer's law explains the relationship between the composition of a mixture and the amount of light it will absorb. Based partly on earlier work by Pierre Bouguer and Johann Heinrich Lambert, it establishes the analytical technique known as spectrophotometry.

1855: Benjamin Silliman, Jr. - Pioneers methods of petroleum cracking, which makes the entire modern petrochemical industry possible.

1856: William Henry Perkin - Perkin's mauve, an early synthetic dye, starts the dye manufacturing industry, one of the first commercially successful chemical industries.

1856: Alexander Parkes - Parkesine, one of the earliest synthetic polymers, is developed.

1857: Friedrich August Kekulé von Stradonitz - Proposed that carbon was tetravalent, or forms exactly four chemical bonds.

1859-1860: Gustav Kirchhoff and Robert Bunsen - Apply spectroscopy to chemical analysis, which lead them to the discovery of caesium and rubidium. Other workers soon used the same technique to discover indium, thalium, and helium.

1862: Alexandre-Emile Béguyer de Chancourtois - published the telluric helix, an early, three-dimmensional version of the Periodic Table of the Elements.

1863: John Newlands - Law of Octaves, an early version of the octet rule and precursor to the Periodic Law.

1864: Lothar Meyer - Early version of the periodic table, with 28 elements organized by valence.

1865: Johann Josef Loschmidt - determined exact number of molecules in a mole, later named Avogadro's Number.

1865: Friedrich August Kekulé von Stradonitz - Working on the work of Loschmidt and others, establishes structure of benzene as a six carbon ring with alternating single and double bonds.

1869: Dmitri Mendeleev - First modern periodic table, with all known elements organized by atomic weights, and as-yet-undiscovered elements correctly placed in their correct locations.

1873: Jacobus Henricus van 't Hoff - developed a model of chemical bonding that explained the chirality experiments of Pasteur and provided a physical cause for optical activity in chiral compounds.

1876: Josiah Willard Gibbs - Publishes On the Equilibrium of Heterogeneous Substances, a compilation of his work on thermodynamics and physical chemistry which lays out the concept of free energy to explain the physical basis of chemical equilibria.

1877: Ludwig Boltzmann - Establishes statistical derivations of many important physical and chemical concepts, including entropy, and distributions of molecular velocities in the gas phase.

1880: Adolf von Baeyer - Synthesis of indigo dye, a milestone in modern industrial organic chemistry which revolutionized the dye industry.

1883: Svante Arrhenius - Developed ion theory to explain conductivity in electrolytes.

1884: Jacobus Henricus van 't Hoff - Publishes Études de Dynamique chimique, the groundbreaking study on chemical kinetics.

1884-1894: Hermann Emil Fischer - Structure and synthesis of glucose and related sugars.

1885: Henry Louis Le Chatelier - Le Chatelier's principle explains the response of dynamic chemical equilibria to external stresses.

1886: Eugene Goldstein - Named the cathode ray, later discovered to be composed of electrons, and the canal ray, later discovered to be positive ions that had been stripped of their electrons in a cathode ray tube.

1891: Vladimir Shukhov - Develops first thermal cracking techniques important to petrochemical industry.

1893: Alfred Werner - Discovers the octahedral structure of cobalt complexes, thus creating the field of coordination chemistry.

1897: Joseph John Thomson - Discovery of the electron using the cathode ray tube.

1898: Wilhelm Wien - Demonstrates that canal rays (streams of positive ions) can be defelected by magnetic fields, and that the amount of deflection is proportional to the mass-to-charge ratio. This discovery would lead to the analytical technique known as mass spectrometry.

1898: Maria Skłodowska-Curie and Pierre Curie - isolation of radium and polonium from pitchblende.

c. 1900: Ernest Rutherford - Discovery of the source of radioactivity as decaying atoms; coins terms for various types of radiation.

1900: Mikhail Semyonovich Tsvet - Invents chromatography, an important analytic technique.

20th century

1902: Gilbert N. Lewis - devises Lewis dot diagrams to describe valence bonding in molecules.

1904: Hantaro Nagaoka - Proposes an early nuclear model of the atom, where electrons orbit a dense massive nucleus.

1904-1914: Frederick Soddy - Discovers that elements can have different isotopes.

1905: Fritz Haber and Carl Bosch - Develop the Haber process for making ammonia from its elements, a milestone in industrial chemistry with deep consequences in agriculture. [25]

1905: Albert Einstein - Explains Brownian motion in a way that definitively proves Atomic Theory.

1907: Leo Hendrik Baekeland - Invented bakelite, one of the first commercially successful plastics.

1909: Ernest Rutherford, Hans Geiger, and Ernest Marsden - Gold foil experiment proves the nuclear model of the atom, with a small, dense, positive nucleus surrounded by a diffuse electron cloud.

1909: Robert Millikan - Oil drop experiment confirms existence of electron as the quanta of electric charge, determines charge/mass ratio of an electron.

1909: S. P. L. Sørensen - Invents the pH concept and develops methods for measuring acidity.

1911: Antonius Van den Broek - Proposes idea that the elements on the periodic table are more properly organized by positive nuclear charge rather than atomic weight.

1912: William Henry Bragg and William Lawrence Bragg - Bragg's law establishes the field of X-ray crystallography, an important tool for elucidating the crystal structure of compounds.

1912: Peter Debye - Developed concept of molecular dipole to describe assymetric charge distribution in some molecules.

1913: Niels Bohr - Introduces concepts of quantum mechanics to atomic structure by proposing what is now known as the Bohr model of the atom, where electrons exist only in strictly defined orbitals.

1913: Henry Moseley - Introduces concept of atomic number to fix inadequacies of Mendeleev's periodic table based on atomic weight, experimentally proves Van den Broek's idea.

1913: Joseph John Thompson - Shows that charged subatomic particles can be seperated by their mass-to-charge ratio, a technique known as mass spectrometry.

1916: Gilbert N. Lewis and Irving Langmuir - Publish "The Atom and the Molecule", the foundation of valence bond theory.

1918: Arthur Jeffrey Dempster - Develops first practical modern mass spectrometer

1922: Otto Stern and Walther Gerlach - establish concept of quantum mechanical spin in subatomic particles.

1923: Gilbert N. Lewis and Merle Randall - Publish Thermodynamics and the Free Energy of Chemical Substances, first modern treatice on chemical thermodynamics.

1923: Gilbert N. Lewis - Develops electron pair theory of acid/base reactions.

1924: Louis de Broglie - Introduces the wave-model of atomic structure, based on the ideas of wave-particle duality.

1925: Wolfgang Pauli - Develops the exclusion principle, which states that no two electrons around a single nucleus may have the same quantum state, described by four quantum numbers.

1926: Erwin Schrödinger - The Schrödinger equation provides a mathematical basis for the wave model of atomic structure.

1926: Gilbert N. Lewis - coins term "photon" to describe the particle of light.

1927: Werner Heisenberg - Develops the uncertainty principle which, among other things, explains the mechanics of electron motion around the nucleus.

c. 1930: Linus Pauling - Pauling's rules form basic underpinning for the use of X-ray crystalography to deduce molecular structure.

1930: Wallace Carothers - Leads team of chemists at DuPont who invent nylon, one of the most comercially successful synthetic polymers in history.

1931: Erich Hückel - Hückel's rule explains when a planar ring molecule will have aromatic properties.

1931: Harold Urey - Discovers deuterium.

1932: James Chadwick - Discovers the neutron.

1932: Linus Pauling - first describes electronegativity as a means of predicting the dipole
moment of a chemical bond.

1935: Arthur Jeffrey Dempster - Discovers Uranium-235, an isotope vital to the development of the atomic bomb and of commercial nuclear power.

1937: Carlo Perrier and Emilio Segrè - First confirmed synthesis of technetium-97, the first artificially produced element, filling a gap in the periodic table. The element may have been synthesized as early as 1925 by Walter Noddack and others.

1937: Eugene Houdry - develops industrial scale catalytic cracking of petroleum for first modern oil refinery.

1938: Pyotr Kapitsa, John Allen and Don Misener - Produced supercooled helium-4, the first zero-viscosity superfluid, a substance that displays quantum mechanical properties on a macroscopic scale.

1939: Linus Pauling - Publishes The Nature of the Chemical Bond, a compilation of a decades worth of work on chemical bonding. It is one of the most important modern chemical texts. It explains hybridization theory, covalent bonding and ionic bonding as explained through electronegativity, and resonance as a means to explain, among other things, the structure of benzene.

1940: Edwin McMillan and Philip H. Abelson - Identification of neptunium, the lightest and first synthesized transuranium element, identified in the products of uranium fission.

1941: Glenn T. Seaborg - Takes over McMillan's work creating new atomic nuclei. Pioneers method of neutron capture and later through other nuclear reactions. Would become the principal or co-discoverer of nine new chemical elements, and dozens of new isotopes of existing elements.

1945: Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell - First confirmed synthesis of Promethium, filling in the last "gap" in the periodic table.

1945-1946: Felix Bloch and Edward Mills Purcell - Discovers the process of Nuclear Magnetic Resonance, an analytical technique important in elucidating structures of molecules, especially in organic chemistry.

c. 1950: Alan Walsh - Pioneered the field of atomic absorption spectroscopy, an important quantitative spectroscopy method that allows one to measure specific concentrations of a material in a mixture.

1951: Linus Pauling - Use of X-ray crystalography to deduce the secondary structure of proteins.

1952: Robert Burns Woodward, Geoffrey Wilkinson, and Ernst Otto Fischer - Discover the structure of ferrocene, leading to a boom in the field of organometallic chemistry.

1953: James D. Watson and Francis Crick - Propose the structure of DNA, opening the door to the field of molecular biology.

1958: Max Perutz and Sir John Cowdery Kendrew - First use of X-ray crystallography to elucidate a protein structure, specifically Sperm Whale myoglobin.

1962: Neil Bartlett - Synthesizes xenon hexafluoroplatinate, showing for the first time that the noble gases can form chemical compounds.

1965: Linus Pauling - Proposes the Close-Packed Spheron Model of the atomic nucleus as a means to explain the specific organization of the atomic nucleus.

1965: Robert Burns Woodward and Roald Hoffmann - Use the symmetry of molecular orbitals to explain the stereochemistry of chemical reactions (the Woodward-Hoffmann rules).

1966: Franklin H. Field and M. S. Burnaby Munson - Develop chemical ionization mass spectrometry, a soft ionization technique that reduced the amount of fragmentation observed during electron ionization.

1975-1976: Richard R. Ernst - Develops the technique of Fourier Transform NMR, greatly increasing the sensitivity of the technique, and opening the door for magnetic resonance imaging or MRI.

1985: Harold Kroto, Robert Curl and Richard Smalley - Discovery of fullerenes, a class of large carbon molecules superficially resembling the geodesic dome designed by architect R. Buckminster Fuller.

1991: Sumio Iijima - First practical production of a type of cylindrical fullerene known as a carbon nanotube, though earlier work had been done in the field as early as 1951.

1995: Eric Cornell and Carl Wieman - Produce the first Bose–Einstein condensate, a substance that displays quantum mechanical properties on the macroscopic scale.

Source : wikipedia

Some Thougths

2007-02-24T03:40:00.000+05:45

Well this blog is kindda experimentation for me . But still i will be trying my best to come up with intresting things for you guys to read . Wish me luck .

Why name a blog chemistry blog?

Well even i dont know the answer to that . I wanted to blog just for sake of fun and while creating this blog i came up with this idea of chemistry blog . Yeha i am kind of chemical lover and well i will be trying to post as regularly as i can.