SANGER-RIEGEL. — SULPHUR TRIOXIDE-SILICON CHLORIDE. 583 



Solid sulphur trioxide did not dissolve in silicon tetrachloride and 

 liquid mixtures of the trioxide and fuming sidphuric acid containing 

 8 percent of water or less, did not mix with the tetrachloride, l)ut such 

 hydrous sulphur trioxide solutions were made to react with it by shak- 

 ing the two for several hours (5^ to 12) at room temperature, or better 

 still by directing a blast of air warmed to 50°, on the I)ottle while on 

 tlie shaker, when the mixing took place in less than an hour. The 

 product after distillation could not be distinguished from that obtained 

 from pure melted sulphur trioxide, except on analysis, when the former 

 was found to contain roughly 14 percent sulphur, the latter 21 percent, 

 and on cooling and seeding with pyrosulphuryl chloride, the latter 

 could be made to crystallize, but not the former. The reason is self- 

 evident, for in the former cases the water was combined with much of 

 the sulphur trioxide, reducing its concentration as such; in the latter, 

 the concentrations remained high, and reaction (2) could take place 

 to a sufficient extent to raise the amount of pyrosulphuryl chloride. 

 The yield (50 percent in the best case) seemed to be better when no 

 water had been used in the sulphur trioxide, and when the proportions 

 were those of two molecules of sulphur trioxide to one of silicon tetra- 

 chloride; an excess of either reagent diminished the action. 



This product was freed from the unaltered reagents by distillation 

 either at atmospheric or at reduced pressure. Its character and our 

 attempts to prepare a pure substance from it are best made evident 

 by the description of two of our most extended experiments. 



101 grams of silicon tetrachloride were added to 100 grams of 93.8 

 percent sulphur trioxide, being 1 molecule of the former to 2 of the 

 latter, and after shaking 5^ hours a pale brown homogeneous liquid 

 was formed which on standing over night deposited a flocculent pre- 

 cipitate and became colorless. 145 grams of the supernatant liquid 

 were distilled at 16 mm. pressure with two condensers inserted between 

 the receiver and the pump; the first was cooled by solid carbon dioxide 

 mixed with absolute alcohol, and was destined to collect sulphur 

 trioxide and silicon tetrachloride; the second was cooled by liquid 

 air, and could therefore condense hydrochloric acid besides any 

 material escaping the first tube.-^^ 76 grams were collected at 42° 

 to 70°. The tube at — 78° contained 9 grams, the liquid air tube. 

 19.5 grams. These were silicon tetrachloride and sulphur trioxide 

 In the subsequent distillations a single condenser cooled by liquid air 



15 For description of the kind of tube used in the liquid air, see Sanger and 

 Riegel, These Proceedings, 47, 697. 



