Halogen Derivatives of Silicopropane, Si₃X₈

Octachlorosilico-propane, Si₃Cl₈, is among the products of the action of chlorine on crude silicon, of which it forms about 0.5 to 1 per cent.; it is separated from the tetrachloride and hexachlorosilico-ethane formed with it by fractional distillation. Its formation, moreover, appears to depend on the presence of magnesium silicide in the crude silicon. Octachlorosilicopropane is a colourless liquid boiling at 215°-218° C.; after solidification it melts at -67° C.; it is decomposed by cold water, forming mesosilico-oxalic acid thus:

+ 6H₂O = + 8HCl.

Octabromosilicopropane, Si₃Br₈, is formed among other products 7 of the action of the silent electric discharge on silicobromoform, SiHBr₃. It is a solid melting at 133° C.