343 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



These results will be discussed, in connection witli 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 

 oxide thus left as residue. In the sulphate, CrolSO^).,, the subjoined 

 percentages of CroOa were found. The braces indicate two different sam- 

 ples of material, to which, however, we are justified in ascribing equal 

 value : 



.542 grm. sulphate gave 

 1.337 



.5287 

 1.033 



.868 



.212 grm. CrA 



.523 



.207 



.406 



.341 



39.114 per cent. ') 

 39.117 " I 



39.153 " J 



39.303 " ") 



39.286 " / 



Mean, 39.1946, ± .0280 



Hence Cr = 53.43. 



From the alum, NH4.Cr(S0i)o.l3H20, we have these percentages of 

 CrjOg. The first series represents a salt long dried under a bell jar at a 

 temperature of 18°. The crystals taken were clear and transparent, but 

 may possibly have lost traces of water,^ which 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 results were obtained 

 quite near those of Berlin. Both of these series are discussed together, 

 neither having any present value : 



Mean. 16.143, ± .0125 

 Hence Cr = 53.46. 



The determinations made by Lefort ' are even less valuable than tliose 

 by Moberg. This chemist started out from barium chromate. which. 



1 .Journ. prakt. Chem., 43, 114. 



2 This objection is suggested by Berlin in .1 note upon Lefort' 

 71, 191. 



'Journ. prakt. Chem., 51, 261. 18.50. 



paper. .Journ. prakt. Chem.. 



