Acetylene [74-86-21] M 26.0, m -80.8°, b -84°, pK -25. If very impure it should be purified by
successive passage through spiral wash bottles containing, in this order, satd aq NaHSO4, H20, 0.2M iodine in
aq KI (two bottles), sodium thiosulfate soln (two bottles), alkaline sodium hydrosulfite with sodium
anthraquinone-2-sulfonate as indicator (two bottles), and 10% aqueous KOH soln (two bottles). The gas was
then passed through a Dry-ice trap and two drying tubes, the first containing CaCl2, and the second, Dehydrite
[Mg(C104)2] [Conn, Kistiakowsky and Smith J Am Chem Soc 61 1868 1939]. Acetone vapour can be
removed from acetylene by passage through H2O, then concd H2S04, or by passage through two gas traps at
-65° and -80°, concd H2SO4 and a soda lime tower, a tower of 1-mesh Al2O3 then into H2SO4 [Org Synth Coll
Vol 1 229 1941,3 853 1955; 4 793 1963]. Sometimes it contains acetone and air. These can be removed by
a series of bulb-to-bulb distns, e.g. a train consisting of a conc H2SO4 trap and a cold EtOH trap (-73° ), or
passage through H2O and H2SO4, then over KOH and CaCl2. [See Brandsma Preparative Acetylenic Chemistry,
1st Edn Elsevier 1971, for pK p15, ISBN 0444409475; 2nd Edn Elsevier 1988, ISBN 0444429603, and Chapter
5 for sodium acetylide.] It is also available commercially as 10ppm in helium, and several concentrations in N2
for instrument calibration. |