74 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



The analysis of silver iodate has also been performed with extreme 

 care by Stas." From 76 to 157 grammes were used in each experiment, 

 the weights being reduced to a vacuum standard. As the salt could not 

 be prepared in an absolutely anhydrous condition, the water expelled in 

 each analysis was accurately estimated and the necessary corrections ap- 

 plied. In two of the experiments the iodate was decomposed by heat, 

 and the oxygen given off was fixed upon a weighed quantity of copper 

 heated to redness. Thus the actual weights, both of the oxygen and the 

 residual iodide, were obtained. In a third experiment the iodate was 

 reduced to iodide by a solution of sulphurous acid, and the oxygen was 

 estimated only by difference. In the three percentages of oxygen given 

 below, the result of this analysis comes last. The figures for oxygen are 



as follows : 



16.976 

 16.972 

 16.9761 



Mean, 16.9747, 



.0009 



This, combined with Millon's series above cited, gives us a general 

 mean of 16.9771, ±.0009. 



Hence Agl = 234.734, ±.0126. 



THE IODINE PENTOXIDE-SILVEK RATIO. 



The ratio between iodine pentoxide and silver has been measured by 

 Baxter and Tilley.^ The oxide was prepared by the careful dehydration 

 of iodic acid, the latter having been made from purified iodine. After 

 weighing, the pentoxide was dissolved in water, and the acid so formed 

 was reduced to hydriodic acid by means of hydrazine. By final titration 

 of the solution with a solution of pure silver, the ratio in question was 

 determined. The ultimate data, with vacuum weights and all corrections 

 applied, are as follows : 



Series I. Tilley. 

 Weight 1^0^. Weight Ag. 



r 6.06570 3.92027)3 



19.48035 6.12611/ 



7.73052 4.99564 64.6223 



12.63909 8.16777 64.6231 



9.49913 6.13841 64.6208 



8.34369 5.39202 64.6239 



8.83155 5.70715 64.6223 



6.77487 4.37803 64.6216 



Mean, 64.6225, ± .0003 



^ Oeuvres Completes, 1, 628. 



-Journ. Amer. Chem. Soc, 31, 201. 1909. 



^ These analyses were inadvertently mixed, and hence are combined in the table. 



Ratio. 



64.6234 



