120 THE ATOMIC WEIGHTS. 



In the single experiment with anhydrochromate 100 AgCl 

 is formed from 151.035 Ag2Cr20,. 



Finally, for the ratio between AgCl and Cr^O.^, 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, 26.6S2, i .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 sul- 

 phate and of ammoniacal chrome alum, and the determina- 

 tion of the amount of chromic oxide thus left as residue. 

 In the sulphate, Cr2(S04)3, the subjoined percentages of 

 Cr,03 were found. The brackets indicate two different 

 samples of material, to which, however, we are justified in 

 ascribing equal value : 



.542 grm. sulphate gave .212 grin. Cr^Oa. 39.1 14 per cent. 



1.337 " .523 " 39.117 " 



.5287 " .207 " 39-153 " 



1.033 " -406 " 39-303 " 



.868 " .341 " 39.286 " 



Mean, 39.1946, dr .0280 



From the alum, (NH J.Cr^lSO J2-24H,0, we have these 

 percentages of Cr^Og. The first series represents a salt long 

 dried under a bell jar at a temperature of 18°. The crys- 

 tals taken were clear and transparent, but may possibly 

 have lost traces of water,t wliicli would tend to increase the 

 atomic weight found for chromium. In the second series 

 the salt was carefully dried between folds of filter paper, and 



* Journ. fiir Prakt. Chem., 43, 114. 



f This objection is suggested by Berlin in a short note upon Lefort's paper. 

 Jouin. fiir Prakt. Chem., 71, 191. 



