350 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



ratios 31 : AgjCrO^ and 31 : Ag2Cr04.4NH3. Thus treated, the weights 

 are as follows, reduced to a vacuum. Eeckoning the salt as 100, the third 

 column gives the percentage of iodine liberated : 



AgMrOi. I Set Free. Percentage. 



.43838 .50251 114.G28 



.90258 1.03432 114.595 



.89858 1.02980 114.603 



.89868 1.03072 114.693 



Mean, 114.630, ± .015 

 Hence Cr = 52.40. 

 The next series, obviously, gives the ratio 31 : AgXr04.4NH3 



Mean, 95.208, ± .0497 

 Hence Cr = 52.03. 



In dealing with the two dichromates Meineke used the acid potassium 

 iodate in place of potassium iodide, the chromate and the iodate reacting 

 in the molecular ratio of 2:1. Tlie thio sulphate was standardized by 

 means of the acid iodate, so that we have direct ratios between the latter 

 and the two chromates. The data are as follows, with the amount of 

 iodate proportional to one hundred parts of the dichromate in the third 

 column : 



K.Cr.O-,. KHI.Oa. Percentage. 



.25090 .16609 66.198 



.25095 .16613 66.200 



.25078 .16601 66.197 



.24979 .16541 66.220 



.24987 .16540 66.192 



.24966 .16543 66.262 



.25015 .16559 66.196 



.25012 .16559 66.204 



.24977 .16546 66.245 



.25034 .16572 66.198 



.25025 .16567 66.202 



.25015 .16568 66.234 



Mean, 66.212, ± .0044 



Hence Cr = 52.14. 



* These figures are not vvhollj' in accord with the percentages of ox3'gen computed by Meineke. 

 I suspect that there is a misprint among his data as published, probably in the second e.xperi- 

 ment, but I cannot trace it with certainty. 



I 



