380 IRON, NICKEL, COBALT, c. 



analysis it follows, that protomuriate of cerium 

 is composed of 



Muriatic acid 0-4609 or 4-625 



Protoxide of cerium 0-684 - 6-862 



As the salt was. neutral, the conclusion to be 

 drawn from this analysis is, that the atomic 

 weight of protoxide of cerium is 6 -862. 



But I think there is reason to suspect that the 

 muriatic acid in this analysis is somewhat over- 

 rated, and the protoxide of cerium somewhat un- 

 derrated : at least, I generally find, that when 

 nitrate of silver is poured into the solution of a 

 metalline salt, the chloride obtained contains 

 traces of the metal previously in combination 

 with the muriatic acid. In order to obtain cor- 

 rect results from the analysis of a metalline mu- 

 riate, the metallic oxide should be thrown down 

 in the first place, by means of an alkaline car- 

 bonate or pure alkali ; and after the metallic ox- 

 ide has been separated by the filter, the liquid is 

 to be neutralized by nitric acid, and the muriatic 

 acid thrown down by nitrate of silver. These 

 considerations induced me to make the following 

 experiments in order to determine the atomic 

 weight of protoxide of cerium. 



i A quantity of oxalate of cerium was ex- 



ments of 1 J 



the author, posed to a red heat, in order to destroy the acid 

 which it contained. The peroxide of cerium 

 thus obtained, was dissolved in muriatic acid, 

 and the liquid was repeatedly evaporated to dry- 



