582 PROCEEDINGS OF THE AMERICAN ACADEMY. 



was continued in the customary way, involving in the earher analyses 

 two evaporations with intermediate filtrations, and corrections with 

 hydrofluoric acid, but these corrections were found to be so small that 

 the accuracy desired did not justify the work necessitated by them. 

 Later therefore only one filtration was made, and the hydrofluoric 

 acid correction left out. In the filtrate from the silica, the sulphur 

 was determined as barium sulphate. 



Chlorine: A bulb containing a known weight was broken in a solu- 

 tion of the sodium hydroxide. The liquid was filtered into a pre- 

 cipitating flask, and, after adding a drop of phenol phthalein, weakly 

 acidified with chlorine-free nitric acid; silver chloride was precipitated 

 from the clear solution, and weighed on a Gooch crucible. 



In order to determine how much silica was carried down by the 

 precipitate, a sample of silicon tetrachloride was treated with sodium 

 hydrate, and the alkaline solution evaporated in a platinum dish; the 

 silica was removed, and the chlorine determined. It was found to be 

 83.3 percent. The same material was then analyzed without remov- 

 ing the silica and there was found 83.6 percent of chlorine. Several 

 other determinations confirmed this result. The amount of inclusion 

 depends mainly upon the dilution at the moment of precipitation, 

 and upon the percentage of silicon in the substance. The dilution 

 was always made considerable, and while silicon tetrachloride contains 

 16.63 percent of silicon, the material analyzed contained one half to 

 one fourth as much. Therefore it seemed safe to assume that the 

 analyses had an accuracy of 3 parts in 1000, or 0.3 percent, which satis- 

 fied the requirement in this work. 



The Mixtures. 



When sulphur trioxide was added to silicon tetrachloride they 

 mixed at once forming at 32° a clear colorless liquid, which after being 

 sealed and standing in the room deposited long white needles like those 

 of sulphur trioxide from which we inferred little or no reaction had 

 taken place, but after this liquid had been heated in an air bath to 50° 

 for 6 hours a reaction took place as shown by the formation of a product 

 boiling between 135° and 150° at atmospheric pressure, whereas sul- 

 phur trioxide boils at 46° and silicon tetrachloride at 57°. A con- 

 siderable deposit of silica also appeared in many of our experiments.^* 



14 Preliminary experiments tried by Mr. Maurice L. McCarthy led to the 

 formation of distillates similar to those described later. 



