256 BAXTER, WEATHERILL AND SCRIPTURE. 



rounded with ice and water. In the seventh distillation at the higher 

 pressure the two most volatile fractions, 3 and 4, were collected for 

 analysis, as well as the two least volatile fractions, 12 and 13 (Fig. 4). 



Unfortunately at this point the apparatus was again opened to the 

 air by the breakage of a capillary. Although the quantity of material 

 was by this time much diminished, about 30 cc, the remainder was 

 introduced into bulb V and the bulb thoroughly flushed out with 

 tetrachloride vapor. Further fractionation at the lower pressure, 

 using carbon dioxide-alcohol as refrigerant, yielded three residual 

 fractions, 9, 10 and 11, while the remainder was collected in the four 

 fractions, 5, 6, 7 and 8. 



Sample I was purified by Dr. E. O. Holmes, Jr., Samples II and III 

 by Dr. Weatherill, and Sample IV by Mr. Scripture. 



The Analysis of Silicon Tetrachloride. 



After being weighed the bulb containing silicon tetrachloride was 

 broken under an excess of sodium hydroxide and the glass was col- 

 lected and weighed. The solution was diluted to considerable volume 

 and made acid with nitric acid, and then was precipitated with a solu- 

 tion of a weighed very nearly equivalent amount of pure silver. The 

 point of exact equivalence between chloride and silver was then found 

 with the assistance of a nephelometer. 



The bulb of material selected for analysis was soaked first in cleaning 

 solution, then for several days in pure water. Sometimes the capil- 

 lary was slightly scratched with a file. Next the bulb, suspended in a 

 platinum wire basket, was weighed under water of known temperature. 

 After being dried with a clean, nearly lintless cloth, the bulb was al- 

 lowed to remain at least over night in a desiccator containing fused 

 potassium hydroxide. Weighing by substitution followed, and the 

 temperature, pressure, and humidity of the balance case were observed 

 at the same time. From the loss in weight under water the volume of 

 the bulb was computed, and then from the atmospheric conditions the 

 buoyant effect of the air on the bulb. In weighing the fractions of 

 Sample IV, the atmospheric density was found from the weight of a 

 sealed, standardized globe. 22 



A solution of about fifty per cent excess of the quantity of pure 

 sodium hydroxide (purified as described on page 247) necessary to react 

 completely with the tetrachloride was filtered into a heavy walled 2 



22 Baxter, Jour. Amer. Chem. Soc, 43, 1317 (1921). 



