80 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



the silver iodide was collected without the addition of silver nitrate, after 

 washing with pure water ; then the dissolved silver iodide was determined 

 in the filtrate and wash water, hy comparing the precipitates produced 

 by the addition of silver nitrate with those formed in standard solutions 

 of hydriodic acid. As a matter of fact, the filtrates were always found 

 to be practically free from silver iodide, while the wash water contained 

 from two to four tenths of a milligram per liter. This difference in solu- 

 bility of the silver iodide in the filtrate and wash waters is probably due 

 to colloidal solubility of this salt in pure water. The loss on fusion of 

 the silver iodide and the asbestos shreds were determined as usual. The 

 almost absolute lack of opalescence in the filtrate when treated with 

 silver nitrate or hydriodic acid is a good proof of the complete absence 

 of chlorine and bromine, since both silver bromide and silver chloride 

 are considerably more soluble than the iodide. 



The vacuum corrections —0.000031 for silver and +0.000102 for 

 iodine were applied. The atomic weight of silver is assumed to be 

 107.930, as before. 



TABLE III. 

 Series V. I : Agl. 



Finally, in order to determine the ratio of silver to silver iodide, the 

 filtrate and wash 'waters were evaporated to very small bulk until the 

 greater part of the nitric acid had been expelled, and then the amount of 

 silver in the residue was determined nephelometrically, after dilution to 

 twenty-five cubic centimeters, by adding an excess of hydriodic acid and 

 comparing with standard solutions of silver. This quantity, which was 



