234 PROCEEDINGS OF THE AMERICAN ACADEMY. 



and the nitrogen- and air purifying trains had short rubber connections 

 only at the beginning. Any one of these gases or any desired mixture 

 could be delivered through the tube in which the boat containing 

 the salt was placed. This tube could be heated to constant temper- 

 atures in an oven consisting of two superimposed solid aluminum 

 blocks.^ 



According to Matignon,^ at about 105° C. neodymium chloride loses 

 five of its six molecules of water of crystallization rapidly, while the 

 sixth molecule appears at 160°. We have determined the melting 

 point of the hexahydrated chloride (made from fraction 2931) to be 

 124°. Thus the drying of the chloride may be caused to take place 

 by a process of double efflorescence, a condition very favorable for the 

 complete elimination of the water. Richards ^ has pointed out that a 

 hydrated salt dried wholly by efflorescence can be freed from moisture 

 much more effectively than one which has been allowed to melt during 

 the dehydration, hence care was taken to keep the temperature below 

 124° until the greater part of the water had been expelled. 



The powdered crystals of neodymium chloride were placed in a plat- 

 inum boat which had been previously weighed in a weighing bottle, 

 and the boat was heated in a current of mixed nitrogen and hydrochlo- 

 ric acid gases at gradually increasing temperatures. The boat was 

 contained in a hard glass tube which formed part of a "bottling 

 apparatus," ^ and this in turn was attached to the systems for puri^'ing 

 the various gases. The temperature was kept below 124° until the 

 larger portion of the water had been expelled. Then it was gradually 

 raised to 200°, and finally the salt was heated at about 330° for one 

 hour in a current of pure hydrochloric acid gas. During the heating 

 there was never the slightest appearance of melting. In the first five 

 analyses the final temperature was higher than in the subsequent ones, 

 and was not far below the fusing point of the anhydrous salt. After 

 the tube had been allowed to cool, the hydrochloric acid was displaced 

 by nitrogen and finally by air, and the boat was transferred to the 

 weighing bottle without exposure to moist air by means of the bottling 

 apparatus. After long standing in a desiccator near the balance the boat 

 and contents were weighed. 



^ Baxter and Coffin, Proc. Amer. Acad., 44, 184 (1909); Jour. Amcr. Chcm. 

 Soc, 31, 20G. 



2 Compt. Rond., 133, 289 (1901). 



3 Zeit. physilv. Clicm., 46, 194 (1903). 



* Richards and Parker, Proc. Amer. Acad., 32, 59 (1S96). 



