SILVER, POTASSIUM, ETC. 25 



ill each experiment, the weights being reduced to a vacuum 

 standard. As the salt could not be prepared in an abso- 

 lutely anhydrous condition, the water expelled in each 

 analysis was accurately estimated and the necessary correc- 

 tions applied. 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 resid- 

 ual 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, dr .ocxjq 



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

 a general mean of 16.9771, ± .0009. 



The ratio between silver and potassium iodide seems to 

 have been determined only by Marignac,* and without re- 

 markable accuracy. In five experiments 100 parts of silver 

 were found equivalent to potassium iodide as follows : 



Mean, 153.6994, ± .0178 



The synthesis of silver iodide has been effected by both 

 Marignac and Stas. Marignac, in the paper above cited, 

 gives these weighings. In the last column I add the ratio 

 between iodine and 100 parts of silver : 



15.000 grm. Ag gave 32.625 Agl. 117.500 



14.790 " 32.170 " 117.512 



18.545 " 40.339 " 1 17-519 



Mean, corrected for weighing in air, 117.5335, i .0036 

 * Berzelius' Lehrbuch, 5th Ed., 3, 1196. 



