It is usually made by distilling tartaric acid with potassium bisulphate at about zoo-250° C., the crude product being afterwards fractionated.
Berzelius (Jahresb., 182 5, 4, p. 91) by the action of chlorine on silicon, and is also obtained when an intimate mixture of silica and carbon is heated in a stream of chlorine and the products of reaction fractionated.
Wailer (Ann., 1857, 104, p. 94), is formed by heating crystallized silicon in hydrochloric acid gas at a temperature below red heat, or by the action of hydrochloric acid gas on copper silicide, the products being condensed by liquid air and afterwards fractionated (0.
It may be solidified to rhombic crystals which melt at 5.4° C. (Mansfield obtained perfectly pure benzene by freezing a carefully fractionated sample.) It boils at 80 4°, and the vapour is highly inflammable, the flame being extremely smoky.
After the reaction is completed, the liquid is acidified with dilute sulphuric acid (1:5) and then shaken with salt solution, separated from the salt solution, washed, dried and fractionated.