MOLYBDENUM. 55 



When a solution of chromate of potash is 

 poured into a fresh solution of protosulphate of 

 iron, there is deposited a dark brown powder, 

 exceedingly similar, in its appearance, to the 

 mineral usually distinguished by the name of 

 chromate of iron. In this precipitate, the iron is 

 in the state of peroxide ; it immediately robs the 

 chromic acid of a portion of its oxygen, and con- 

 verts it into cleutoxide. The mineral has not yet 

 been analyzed with the requisite care ; but from 

 the analysis of Klaproth, it seems probable that 

 it is composed of 



2 atoms deutoxide of chromium 9 

 1 atom peroxide of iron . 5 



14 



I am disposed, therefore, to consider it as a bi- 

 chromite of iron, the chromate of iron, proba- 

 bly, does not exist. 



Similar phenomena take place when chromate 

 of potash is dropped into protosulphate of man- 

 ganese. Probably the black precipitate, which 

 I have not examined, is a chromite of manga- 

 nese. 



SECT. IV. 



OF THE ATOMIC WEIGHT OF MOLYBDENUM. 



BUCHOLZ first showed that molybdenum com- 

 bines with three proportions of oxygen. The 



