12 THE ROYAL SOCIETY OF CANADA 



of solution we had found the ratio of solute to solvent. At least 

 two such determinations were made for each point on the temperature 

 scale examined. 



Two methods were employed in analyzing the solutions. In the 

 majority of cases the solutions were transferred to weighed porcelain 

 dishes, several drops of acid were added and the water and acid then 

 evaporated on the water bath. After drying the residue at 110°, 

 it was weighed. For the platinum solutions that were free from 

 ammonium salts this gave results quite accurate enough. In the 

 case of the ammonium chloride and bromide solutions of the platinum 

 salts, and also for the iridium solutions, owing to the unstable character 

 of the iridium chloriridate, it was found necessary, to reduce the salt 

 to metal and to weigh the residue in this form, after completely 

 volatilizing the ammonium chloride or bromide. 



The second method of analysis consisted in the determination of 

 the amount of salt present colormetrically. As suggested by Archi- 

 bald, Wilcox, and BuckleyS this can be done quite accurately for the 

 chloroplatinate solutions and the same method was found to give 

 good results in the case of dilute solutions of the bromoplatinate and 

 chloriridate. Standard solutions of these two salts were prepared 

 and the depth of colour of the unknown solutions compared with these. 

 The bromoplatinate gives red and the chloriridate brownish red 

 solutions. 



A few experiments were first made for the purpose of determining 

 for what length of time the solutions must be rotated in order to reach 

 the saturation point for any particular temperature. With this 

 point in view, three tubes containing water and salt were rotated 

 in the bath and removed at different intervals and the contents ana- 

 lyzed. It was found that at temperatures above 20°, saturation was 

 attained in four hours; while below this temperature two or three 

 hours further rotation was necessary. In order to insure a safe 

 margin, the rotations were continued for a period of twelve hours 

 for all temperatures below 20°. 



Soluhilily of Ammonium Chloroplatinate in Water. 



The variation of the solubility of ammonium chloroplatinate in 

 water with temperature was first studied. 



The results obtained are set forth in Table I. The values repre- 

 sent the amounts of salt, in grams, dissolved in 100 grams of water. 



1 Jour. Am. Chem. Soc, 30, 747 (1908). 



