346 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



parts of chloride of silver, the quantities of chromic chloride stated in 

 the third of the subjoined columns : 



.23G7 grm. CrClj gave .6396 grm. AgCl. 37.007 



.2946 " .7994 " 36.853 



.2593 " .7039 " 36.838 



.4935 " 1.3395 " 36.842 



.5850 " 1.5884 " 36.830 



.6511 " 1.76681 " 36.852 



.5503 " 1.49391 " 36.836 



Mean, 36.865, ± .0158 



The first of these figures varies so widely from the others that we are 

 justified in rejecting it, in which case the mean becomes 36. 842, ±.0031. 

 Hence Cr = 52.046. 



Siewert also made two analyses of silver dichromate by the following 

 process. The salt, dried at 120°, was dissolved in nitric acid. The silver 

 was then thrown down by hydrochloric acid, and, in the filtrate, chro- 

 mium hydroxide was precipitated by ammonia. Eeduced to a uniform 

 standard, we find from his results, corresponding to 100 parts of AgCl, 

 AgaCrjO^ as in the last column : 



.7866 grm. Ag.CrA gave .52202 AgCl and .2764 CrA- 150.684 

 1.089 " .72249 " .3840 " 150.729 



Hence Cr = 52.14. 



Berlin's single determination of this ratio gave 151.035. Taking all 

 three values together as one series, they give a mean of 150.816, ±.074. 



Siewert's percentages of CroO.,. obtained from AgaCrjO- are as follows, 

 calculated from the above weighings: 



35.139 

 35.262 



Mean, 35.2005, ± .0415 

 Hence Cr = 51.983. 



Combining, as before, with Berlin's single result, giving the latter 



equal weight with one of these, we have a general mean of 35.236, ±.0335. 



For the ratio between silver chloride and chromic oxide, Siewert's two 



analyses of the dichromate give as follows. For 100 parts of AgCl we 



have of Cr^Og : 



52.948 

 53.150 



Mean, 53.049, ± .068 

 Hence ('r = 52.041. 



