BAXTER AND CHAPIN. 



ATOMIC WEIGHT OF NEODYMIUM. 



239 



The Specific Gravity of Neodymium Chloride. 



Although Matignon ^ had already found the density of anhydrous 

 fused neodymium chloride at 18° referred to water at 4° to be 4.195, 

 for the purpose of confirmation this constant was redetermined by dis- 

 placement of toluol. On account of the difficulty of removing air from 

 porous material the salt was fused for these determinations instead of 

 being dried. The pycnometer employed was one of special form, modi- 

 fied by Baxter and Hines.^ 



The salt was first carefully dried and then finally fused in a current 

 of hydrochloric acid gas in a small platinum boat, as previously de- 

 scribed. The boat and contents were then weighed in a small weighing 

 bottle to which they were transferred by means of the bottling apparatus. 

 The salt was next quickly covered with dry toluol and a special pycno- 

 meter stopper was substituted for the ordinary stopper of the weighing 

 bottle. Entangled air was removed by exhaustion in a desiccator and 

 finally the toluol was adjusted to a mark in a capillary outlet tube in 

 the usual way, after the temperature of the system had been carefully 

 adjusted to 25°. In order to avoid evaporation of the toluol through 

 the ground joint of the .pycnometer this was made tight by means of a 

 weighed quantity of syrupy phosphoric acid. The toluol content of the 

 system being known, the displaced toluol could be found. The specific 

 gravity of the toluol at 25° referred to water at 4° was determined in 

 the same pycnometer to be 0.8G36, while Jones'^ in earlier experiments 

 with a different pycnometer found the specific gravity of the same 

 sample to be 0.8G33. 



A part of the difference between this value and ]\Iatignon's can be 

 explained by the diff"erent temperatures at which the determinations 

 were made. 



^ Compt. Rend., 140, 1340 (1905). 

 2 Amer. Chem. Jour., 31, 222 (1904). 



' Baxter and Jones, Proc. Amer. Acad., 45, 155 (1910) ; Jour. Amer. Chem. 

 Soc, 31, 314. 



