CHROMIUM. 239 



4.6680 grm. Ag 2 CrO 4 gave 4.027 grm. AgCl and 1.0754 grm. Cr 2 O 3 . 

 3.4568 " 2.983 " .7960 



2.5060 " 2.1605 " .5770 " 



2.1530 " 1.8555 " -4945 



4-3335 g rm - Ag 2 Cr 2 O 7 gave 2.8692 i.53 " 



From these weighings three values are calculable for the atomic weight 

 of chromium. The three ratios upon which these values depend we will 

 consider separately, taking first that between the chromic oxide and the 

 original silver salt. In the four analyses of the normal chromate the 

 percentages of Cr 2 3 deducible from Berlin's weighings are as follows : 



Mean, 23.014, =fc .on 



And from the single experiment with Ag 2 Cr 2 7 the percentage of Cr 2 O, 

 was 35.306. 



For the ratio between Ag 2 Cr0 4 and AgCl, putting the latter at 100, we 

 have for the former : 



115-917 

 115.883 

 115.992 

 116.033 



Mean, 115.956, rb .023 



In the single experiment with dichromate 100 AgCl is formed from 

 151.035 Ag. 2 Cr 2 O 7 . 



Finally, for the ratio between AgCl and Cr 2 3 , the five experiments of 

 Berlin give, for 100 parts of the former, the following quantities of the 

 latter : 



26.705 



26.685 



26.707 



26.650 



26.662 



Mean, 26.682, .0076 



These results will be discussed, in connection with the work of other 

 investigators, at the end of this chapter. 



In 1848 the researches of Moberg* appeared. His method simply 

 consisted in the ignition of anhydrous chromic sulphate and of am- 

 monium chrome alum, and the determination of the amount of chromic 



* Journ. fi'ir Prakt. Cheni., 43, 114. 



