SANGER-RIEGEL. — SULPHUR TRIOXIDE-SILICON CHLORIDE. 587 



times, with a seed of pyrosulphuryl chloride, the separation taking 

 place in order at —65°, —60°, —60°, and —60°; the crystals thus 

 purified weighed 3.5 grams, and their analysis (15, IG) is given 

 below. The mother liquors were then combined, and a crystalliza- 

 tion from a silicon oxychloride seed attempted, but it failed, for only 

 at — 78° could crystals be obtained, and at that low temperature, 

 crystallization was spontaneous; nevertheless, the crystallization was 

 repeated twice, and the final crystals analyzed (17). The analysis of 

 the original 53 grams is also given (18). 



s Si ci 



(14) 23.98% 3.7 % 40.02% 



(15) 24.28 3.78 39.57 



(16) 24.03 3.85 39.38 



(17) 23.62 4.07 40.08 



(18) 23.26 4.90 41.61 



The composition had not changed markedly; (14) has more sulphur 

 and less silicon than (18) which would point to a concentration of 

 pyrosulphuryl chloride; the fact that it crystallized at —60° rather 

 than at —78° also supports this assumption, but at —60° the super- 

 cooling is still considerable; (15) and (16) differ too little from (14) to 

 have a meaning, so that neither the analysis nor the crystallization 

 with pyrosulphuryl chloride show that all the pyrosulphuryl chloride 

 is present as such. The failure of crystallization with silicon oxy- 

 chloride is reflected in the analysis (17) which hardly differs from (18) 

 the original material, showing that the silicon oxychloride is not present 

 free. 



The experiments described above show why we did not succeed 



in obtaining a pure substance from our product either by fractional 



distillation or crystallization; an additional experiment might be 



mentioned as having led to the same result. A preparation similar 



to the previous one was fractionally distilled 5 times, at atmospheric 



pressure, using a dephlegmator, and yielded two fractions boiling over 



several degrees: 



s ci 



(26) 145-149° 15.3% 50.6% 



(27) 149-157° 17.1 50.7 



But in spite of our failure to isolate the pure substances, our analyses 

 established the nature of the two compounds of which tliis mixture is 

 made up. P'or this discussion we have collected all the complete 

 analyses already given and all the others made by us in a table. Of 



