58 PROCEEDINGS OF THE AMERICAN ACADEMY. 



afterwards by titrating back to the neutral point with a weak acid solu- 

 tion, and it is therefore necessary to obtain in the first place maguesic 

 chloride containing its full complement of acid. 



The method was then modified by conducting the ignition of the double 

 salt in a tightly covered platinum crucible in a stream of hydrochloric 

 acid, instead of air. That a considerable quantity of oxychloride was 

 usually formed, even under these conditions, was easily ascertained by dis- 

 solving the resulting product in water, when the oxychloride remained as 

 an insoluble residue. In two or three cases, however, the amount of oxy- 

 chloride formed was comparatively small ; hence it was hoped that, if the 

 right conditions could be found, the chloride might be obtained in a pure 

 state. Another series of experiments with a modified apparatus was 

 therefore undertaken. The expulsion of the ammonic chloride was con- 

 ducted in a combustion tube and the number of drying tubes was increased, 

 so that the hydrochloric acid gas might be as free as possible from water. 

 The heat was applied very gradually, in order that the double chloride 

 might be almost anhydrous before the sublimation of the ammonic chloride 

 began. This method gave better results. It was observed that in two 

 or three experiments, where the conditions had been unusually favorable, 

 the resulting chloride gave a clear solution ; and it seemed therefore 

 probable that, if an apparatus could be devised to deliver a rapid stream 

 of hydrochloric acid gas entirely free from aqueous vapor, the method 

 might be successful. 



Assuming that these conditions might be fulfilled, another difficulty 

 remained to be overcome ; for even if the magnesic chloride could be 

 obtained in the combustion tube free from water and oxychloride, the 

 problem still remained to weigh the salt without foreign admixture. If 

 the boat were allowed to remain in the tube until cool, and then removed 

 to a weighing bottle, the salt must absorb a very notable quantity of 

 moisture from the air in the operation, however quickly this operation 

 might be performed. The boat cannot be transferred to another tube 

 and reheated, as the moisture present reacts upon the chloride, forming 

 some oxychloride and liberating h3Tlrochloric acid. If it is taken from 

 the combustion tube while hot and allowed to cool in a weighing bottle, 

 the same effect is produced. Dumas had met with the same difficulties 

 in his work with this method, and he endeavored to compromise matters 

 by lemoving the boat from the combustion tube when it had only partly 

 cooled. As his subsequent results proved, however, the moisture from 

 the air reacted upon the chloride, forming some oxychloride, which 

 interfered seriously with the accuracy of his work. To obviate this 



