198 ACIDIFIABLE COMBUSTIBLES. 



Now, from the experiments of Berzelius, men- 

 tioned in the beginning of this section, it is clear 

 that the weights of the silicon and oxygen are 

 nearly equal. Since the atomic weight of silica 

 is 2, and of oxygen 1, it is evident that the 

 atomic weight of silicon is also 1. The true 

 composition of silica is therefore 



1 atom silicon 1 

 1 atom oxygen 1 



SECT. IV. 



OF THE ATOMIC WEIGHT OF PHOSPHORUS. 



PHOSPHORUS enters into chemical combinations 

 both with hydrogen and oxygen ; with the 

 former it constitutes only gaseous, with the 

 latter, only solid compounds. Its combinations 

 with oxygen are phosphorous and phosphoric 

 acids combinations of great importance in the 

 animal, and not without interest in the mineral 

 kingdom. Let us first investigate the atomic 

 weight of phosphoric acid. It will then be easy 

 to determine the composition of phosphorous 

 acid. 

 Atomic 1. Phosphoric acid forms soluble and cryslal- 



weight of 1 1 i ^ r 



phosphoric lizable salts with the alkalies. Or these none is 

 better known than phosphate of soda, which 

 being employed as a medicine, is prepared by 



