On Trihasic Phosphoric Acid. 173 



Herntz, in working on the same subject (1847), found that 

 under ordinary conditions, phosphate of lead will always 

 take down a fixed part of the lead salt, and (in' case chlorides 

 are present in the solution), chloride of lead. The lead 

 salt thus taken down seems to he always h of the phosphate of 

 lead. This tendency of the phosphate will also hold good 

 with other oxyds than oxyd of lead. 



And in the formation of minerals of this order, as Apatite, 

 Pyromorphite and others, conditions must have prevailed that 

 were favorable to their formation and separation from the 

 surrounding rock. It is also apparent that the composition of 

 these minerals in connection with this tendency of the phos- 

 phate proper, will throw light on the probable state in which 

 their constituents existed in the moment of, and on the chemi- 

 cal and physical forces that were active in, their formation. 



Berzelins then analyzed phosphates of baryta, lead, silver, 

 soda and ammonia, which, independently of the water con- 

 tained in them, represent to 100 of phosphoric acid, the fol- 

 lowing amounts of oxygen in the base: 



11.246 



11.27 



In all these experiments, which were made with the greatest 

 care, as might be expected from Berzelins, phosphoric acid was 

 determined by loss. He gave special attention to the compounds 

 of phosphoric acid with lime, and prepared and analyzed a 

 great number of them. 



2. In comparing now the different conditions of saturation of 

 phosphoric acid, the oxygen of the acid was 2, .'! and o' time- ae 

 much as the oxygen of the base. Phosphoric acid would then- 

 fore contain 67.5 p. c. of oxygen, or more than 200 of oxygen 

 to 100 phosphorus, an amount which deviates so far from that 

 actually found by experiment, that the law as to the saturation 



MAY, 1869. 12 Asx. Ltc. Nat. Hist., Vol. IX. 



