Usually nitrogen and argon environment is used during organic synthesis, but not the helium environment?
Helium is very light and very easy difffuse through many materials, it is very difficult to liquefy, it is difficult to store.
Helium is too expensive (~$3/Nm3 ) and its reserves are limited. With the current volume of consumption, its reserves will be depleted within the next 300 years.
http://minerals.usgs.gov/minerals/pubs/commodity/helium/mcs-2012-heliu.pdf
http://www.forbes.com/sites/timworstall/2012/08/27/what-great-helium-shortage/
Helium is very light and very easy difffuse through many materials, it is very difficult to liquefy, it is difficult to store.
Helium is too expensive (~$3/Nm3 ) and its reserves are limited. With the current volume of consumption, its reserves will be depleted within the next 300 years.
http://minerals.usgs.gov/minerals/pubs/commodity/helium/mcs-2012-heliu.pdf
http://www.forbes.com/sites/timworstall/2012/08/27/what-great-helium-shortage/
Argon is heavier than oxygen, so for anaerobic conditions, it is the gas of choice as it will easily displace the O2. Nitrogen is cheaper than argon, so for anaerobic reactions, a lot can be used to essentially blow away all the O2. Because of the expense of argon, balloons are often used instead of a continuous flow. And as Andrei said, the helium is scarce and expensive.
as per now the cost of helium is down as new natural sources have been found, but the main problem with helium Inhaling helium can lead to loss of consciousness and cerebral arterial gas embolism, which can temporarily lead to complete blindness. Blood vessels in the lungs will first rupture and allow the gas to gain access to the pulmonary vasculature and subsequently the brain.
http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/Main_Group_Elements/Group_18%3A_The_Noble_Gases/Chemistry_of_Helium
@ gaurav, I thankful for your kind concern and answer. But i have another query related to your answer. If helium has so much adverse effects then why it is used in oxygen cylinder of a diver.
Dear Arvind, i agree with your query but helium is much less soluble in water than many other gases, such as nitrogen. The low solubility means it does not enter the blood stream, even under pressures commonly experienced by deep sea divers.
http://www.pa.msu.edu/sciencet/ask_st/082593.html
While helium has a lower solubility in blood, and thus has a smaller tendancy to cause the bends, But if you do get the bends with helium it is much worse, helium has the ability to diffuse through tissues into places where nitrogen can not reach.
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