Aug 182015
 

he2  he1

The first evidence of the existence of helium was found on this date in 1868 as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was initially assumed to be sodium. On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the solar spectrum, which he named the D3 Fraunhofer line because it was near the known D1 and D2 lines of sodium. He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος (helios).

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Helium is actually the second most abundant element in the universe but it does not usually exist in a free state on earth for very long. Being less dense than air it rises in the atmosphere and escapes. Hence it was unknown to science for so long – that, and the fact that it is colorless, odorless and tasteless.

In 1882, Italian physicist Luigi Palmieri detected helium on Earth, for the first time, through its D3 spectral line, when he analyzed the lava of Mount Vesuvius. On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare earth elements) with mineral acids. Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas liberated by sulfuric acid, he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun. These samples were identified as helium by Lockyer and British physicist William Crookes. It was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala in Sweden, who collected enough of the gas to accurately determine its atomic weight. Helium was also isolated by the U.S. geochemist William Francis Hillebrand prior to Ramsay’s discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen.

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In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than one degree Kelvin (one degree above absolute zero). He tried to solidify it by further reducing the temperature but failed because helium does not solidify at atmospheric pressure. Onnes’ student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of helium in 1926 by applying additional external pressure.

In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero, a phenomenon now called superfluidity. This property leads it to do some crazy things such as climbing out of its own container.

Helium exists in Earth’s atmosphere only because it is constantly resupplied from two sources – decay of radioactive elements on Earth, and cosmic rays, about 9% of which are high energy helium nuclei. The helium we buy in cylinders is produced by the natural decay of radioactive elements in the earth’s crust – principally thorium and uranium. Radioactive decay of uranium and thorium produces about 3,000 metric tons of helium a year.

Current world production of helium is over 30,000 metric tons a year. (Helium has been accumulating for many millions of years in a few natural gas fields, therefore we can currently extract more each year than is being created by uranium and thorium decay.) So, helium is a (sort of) renewable resource, if we do a little better at conservation than we currently are.

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Most people are familiar with helium through its use in balloons and airships. This is a very minor part of the total world production. Mostly it is used for cooling to very low temperatures, and in controlled mixtures of gases for welding, deep sea diving, and so forth. About 25% is used in cooling, such as for the superconducting magnets in MRI scanners.

he4

Helium has practically no applications in gastronomy, although in the current fad of “molecular” cooking one or two chefs have found ingenious ways to use it. For example, at Alinea in Chicago they make an edible helium filled balloon. The balloon is made from apples and sugar syrup, which you pop with your mouth, inhale the helium, talk like a chipmunk for a minute, then eat the balloon. It was once rumored that Sam Adams was making a beer sparkling with helium, but this was a hoax. However, once in a while people experiment, particularly in Germany, with the idea of pressurizing regular beer with helium, which produces a beer that raises the pitch of your voice and gets you very drunk very quickly. I’ve also seen a suggestion of using helium in 3-D printers that make floating images. The main company for these printers is Flogos (Floating logos). The printers produce large objects in the shape of your company logo which, when cut from the printer, float off into the sky. These objects are a mix of a tight soap foam filled with helium. Since foams are an essential part of gastronomy there is no reason, in theory, why you cannot replace the soap foam with an edible foam such as whipped cream or meringue. This would give “floating islands”( îles flottantes) a whole new meaning !! (see http://www.bookofdaystales.com/bastille-day/ ).

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Given that I don’t have a handy helium cylinder and the time to experiment, I’ll settle for foams and maybe you can imagine them filled with helium. In molecular cooking nowadays chefs make foams using a foam siphon which rapidly aerates any liquid with nitrous oxide. For the foam not to collapse immediately it must contain a stabilizer, such as gelatin, lecithin, protein, or fat. If you don’t have a foam siphon, an immersion blender works just fine.

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