colourless odourless gas
Non-flammable gases. Containers may explode when heated. Ruptured cylinders may rocket.
Argon is rendered oxygen-free by passage over reduced copper at 450o, or by bubbling through alkaline pyrogallol and H2SO4, then dried with CaSO4, Mg(ClO4)2, or Linde 5A molecular sieves. Other purification steps include passage through Ascarite (CARE: asbestos impregnated with sodium hydroxide), through finely divided uranium at about 800o and through a -78o cold trap. Alternatively the gas is passed over CuO pellets at 300o to remove hydrogen and hydrocarbons, over Ca chips at 600o to remove oxygen and, finally, over titanium chips at 700o to remove nitrogen. It has also been purified by freeze-pump-thaw cycles and by passage over sputtered sodium [Arnold & Smith J Chem Soc, Faraday Trans 2 77 861 1981]. Arsenic acid (arsenic pentoxide hydrate, arsenic V oxide hydrate, orthoarsenic acid) [12044-50-7] M 229.8 + xH2O, pK 1 2.26, pK 2 6.76, pK 3 11.29 (H3AsO4). The acid crystallises from concentrated solutions of boiling conc HNO3 as rhombic crystals. Dry it in a vacuum to give the hemihydrate (hygroscopic). Heating above 300o yields As2O5. [Thaler Z Anorg Allgem Chem 246 19 1941, Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 601 1963.]
Gas as shield in gas metal-arc welding, in metal processing; carrier in gas-liquid and gas-solid chromatography; gas filler for incandescent light bulbs. Gas in fluorescent tubes analogous to neon lights, but produces a blue-purplish light; in rectifier tubes; in thermometers above mercury; in lasers; wherever an inert atmosphere is desired and the much cheaper nitrogen cannot be used; in ionization chambers and particle counters; in mixtures with He and Ne in Geiger counters; in argon-oxygen-decarburizing process for stainless steel; in manufacture of semiconducting devices; in gas mixtures as the working fluid in plasma arc devices. Liquid as cryogen to produce low temperetures. The isotope 40Ar is always found in minerals contg potassium, since it is a product of 40K decay; measuring the amount of 40Ar and 40K can be used for determining the geologic age of minerals and meteors.
A colorless odorless noncombustible gas. Heavier than air and can asphyxiate by displacement of air. Exposure of the container to prolonged heat or fire can cause Argon to rupture violently and rocket . If liquefied, contact of the very cold liquid with water may cause violent boiling. If the water is hot, there is the possibility that a liquid "superheat" explosion may occur. Contacts with water in a closed container may cause dangerous pressure to build.
Vapors may cause dizziness or asphyxiation without warning. Vapors from liquefied gas are initially heavier than air and spread along ground.
These substances undergo no chemical reactions under any known circumstances. They are nonflammable, noncombustible and nontoxic. They can asphyxiate.