SANGER- RIEGEL. — SULPHUR TRIOXIDE- SILICON CHLORIDE. 593 



Besides these, several incomplete analyses show similar proportions : 



s 81 ci 



(3) 14.50 10.18 — 



(24) 16.7 — 49.9 



(26) 15.3 — 50.6 



The results leave much to be desired but certainly indicate that 

 the two products were formed approximately in the proportions re- 

 quired by the reaction: 



2SO3 + 2SiCl4 = S2O5CI2 + SiaOCle (1) 



In the majority of analyses percentages were found indicating a 

 decided excess of pyrosulphuryl chloride, and a smaller proportion of 

 silicon oxychloride; the silicon varying from 7.75 to 3.7, instead of 

 being 11.31; the sulphur varied from 19.6 to 24.28 instead of being 

 12.82. The formation of more pyrosulphuryl chloride, and the de- 

 struction of silicon oxychloride is accounted for by the reaction: 



SiaOCle + 6SO3 = 2SiOo + 3S2O5CI2 (2) 



An especially large percent of sulphur indicating a great excess of 

 pyrosulphuryl chloride was obtained from a specimen which had stood 

 3 summer months undistilled, that is, with the low-boiling portions 

 containing the excess of sulphur trioxide still unseparated from the 

 higher boiling portions. It was contained in a glass-stoppered bottle 

 under a bell-jar whose atmosphere was dried by phosphorus pcntoxi<le. 

 Comparing this material with a similar one, which had been heated 

 for 6 hours and had not stood at all, it was found that the higher boiling 

 fraction had increased on standing from 3 percent to 38 percent, the 

 solid deposited rising at the same time from 2.3 percent to 23 percent; 

 in another more favorable case the figures for a similar mixture heated 

 for 6 hours were 15 percent of higher boiling fraction, and 8 percent 

 solid. In all three cases two molecules of sulphur trioxide had been 

 used to each molecule of the silicon tetrachloride. Reaction (1) calls 

 for equal molecules of the two, while (2) requires six molecules of the 

 trioxide to each one of the oxychloride already formed, but no more 

 silicon tetrachloride. This action should be reflected in the lower 

 boiling fraction in an increase in the proportion of silicon tetrachlo- 

 ride, evidenced by a higher percentage of chlorine; an analysis showed 

 that it contained, in the case of the material which stood 3 months, 

 65.5 percent of chlorine, whereas the original mixture of silicon 

 tetrachloride and sulphur trioxide contained only 42.95 percent; this 

 shows that the action is correctly interpreted by reaction (2). It is 



