BAXTER AND STEWART. 



PRASEODYMIUM CHLORIDE. 



185 



In order to find out the composition of the insoluble substance, 

 amounts large enough to be analyzed were prepared by dehydrating 

 the crystals with the usual care, and then fusing the salt for periods 

 from one-half hour to one hour in a current of dry hydrochloric acid 

 gas. The product was then treated with water, and as soon as the 

 soluble portion of the salt had dissolved, the insoluble residue was col- 

 lected upon a small weighed platinum-sponge Gooch crucible, dried 

 and weighed. The residue, which was distinctly crystalline, did not 

 change in appearance during the drying, so that it is improbable that 

 its composition was appreciably altered during this treatment. The 

 praseodymium content of the residue was then determined by dissolv- 

 ing the residue from the crucible in dilute hydrochloric acid, precipitat- 

 ing the base with ammonium oxalate, collecting the precipitate upon a 

 filter, and igniting in a weighed platinum boat. The weight of the 

 black oxide Pr 4 0; was checked by igniting the residue in a stream 

 of hydrogen and reweighing. The weights of oxide obtained in 

 two experiments correspond very closely to the weight which should 

 be obtained, assuming the residue to be praseodymium oxychloride, 

 PrOCl. About 6 grams of anhydrous salt were used in each experi- 

 ment. 



The composition of the residue was further checked by determining 

 the chlorine content. Residues were collected and weighed as above, 

 and then after solution in dilute nitric acid, the chlorine was precipi- 

 tated as silver chloride, collected and weighed. During the solution 

 of the residue the crucible and contents were placed in a closed tube 

 through which a current of air was passed into a solution of ammonia, 

 so that in case chlorine was liberated during the solution, it would be 



