CHROMIUM. 



245 



tated its solution with mercurous nitrate, and ignited the precipitate, 

 with the subjoined results. Vacuum weights are given ; 



Am. 2 Cr. 2 O r Cr 2 O s . Percent. Cr 2 O s . 



2.0416 1.2316 60.325 



2.1618 1.3040 60.320 



2.0823 1.2562 60.328 



2.1913 1.3221* 60.335 



2.0970 1.2656 60.353 



Mean, 60.332, .0037 

 Rawson found, 60.346, .0046 



General mean, 60.337, =b .0029 



The chromate of silver, Ag. 2 Cr0 4 , and the ammonio-chromate, 

 Ag,Cr0 4 .4NH 3 , both prepared with all necessary precautions to insure 

 purity, were first treated essentially as in Berlin's experiments, except 

 that the traces of silver chloride held in solution by the chromic chloride 

 were thrown out by sulphuretted hydrogen, estimated, and their amount 

 added to the main portion. Thus the chief error in Berlin's work was 

 avoided. I subjoin the data obtained, with vacuum standards, as usual. 

 All of Meineke's results are so corrected : 



Ag.CrO,. 



2.7826 

 3.2627 

 3.6362 

 4.6781 

 3-2325 

 3-9I37 



AgCL 



2.4047 

 2.8199 

 3.1416 

 4.0414 

 2.7930 

 3-3805 



.6384 



.7480 



8338 



1.0726 



-74H 

 .8976 



Hence we have the following ratios, as in the case of Berlin's data : 



Percent. Cr. 2 O s . looAgCl : Ag^CrO^. looAgCl : 



22.943 "5-7I5 26.548 



22.926 "5.703 26.526 



22.931 115.744 26.602 



22.928 115.754 26.601 



22.924 "5.736 26.531 



22.935 "5-773 26.552 



Mean, 22.931, .0019 

 Berlin, 23.014, =t .0110 



Mean, 115.737, .0072 Mean, 26.560, .0093 

 Berlin, 115.956, db .0230 



General mean, 22.934, =h .0018 General mean, 115.760, .0069 



With the ammonio-chromate Meineke found as follows : 

 ' AgCL Cr,O,. 



4.1518 

 4.2601 

 5.9348 



2.9724 

 3.0592 

 4.2654 



794 



.8125 



1.1317 



* Calculated back from Meineke's value for Cr, to replace an evident misprint in the original. 



