186 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



caught in the ammonia. The results of the chlorine determinations 

 check closely those of the praseodymium determinations. 



Since it is obvious that, if the oxychloride is formed from the tri- 

 chloride, a loss in weight must occur, further experiments were carried 

 out to discover whether during the formation of the larger amounts 

 of insoluble residue, when the fusion is prolonged, the loss in weight 

 of the salt corresponds to the weight of residue produced. In these 

 experiments the hydrated salt was first very carefully dried, then 

 quickly fused and weighed. During this treatment little if any in- 

 soluble material is formed. Then the boat with the salt was returned 

 to the quartz tube, and after the apparatus had been thoroughly 

 swept out with dry hydrochloric acid, the salt was brought to the 

 fusing temperature, which was maintained for one hour in every case. 

 After the salt had been reweighed, the insoluble residue was determined 

 as previously described and a few tenths of a milligram of salt which 

 sublimed from the boat to the quartz tube were dissolved in water, 

 the solution was evaporated and the residue was heated and weighed. 

 The weight of sublimed material was of course added to the weight of 

 the fused salt before determining the loss in weight during fusion. 



