ffom the Oiiralian Mountains in Siberia. 7 



From the above analysis it appears that the chromate of 

 iron Qf Siberia contains in the 100 parts. 



Oxide of chrome - 53 



Oxide of iron - - 34 



Alumine - - - U 

 Silica - - , 1 



99 

 Traces of manganese and loss 1 



100 



These results are nearly similar to what M. Vauquelin. 

 obtained from the chromate of Var. 



Chromic acid - - 43 ^ 



Oxide of iron - - 34*7 ^ 



Alumine - _ _ gO'S 



Silica - - « 2 



100 



Does the chrome exist in the state of acid or in that of 

 oxide in the mineral termed chromate of iron ? M. Godon 

 de Saint-Mesmin, in a memoir upon the combinations of 

 chromic acid, read at the National Institute, has discussed 

 this question, and is inclined to think that it is in the state 

 ©f oxide. M. Vauquelin, in his report of this memoir, 

 seems disposed to adopt the same opinion. I shall mere- 

 ly state, in support of this idea, an experiment which 

 renders it probable. If the green oxide of chrome be 

 gently calcined with pure potash, it is almost immediately 

 brought to the state of an acid : we are therefore not war- 

 ranted in asserting that chrome exists as an acid in the 

 chromate of iron, while by the presence of potash this con- 

 version of the oxide is rendered likely. It is then, at least, 

 highly probable that the mineral which till now has re- 

 ceived the name of chromate of iron, is, in fact, no other 

 than a combination of the oxides of iron and chrome 



Since I finished my examination of the chromate ^iron 

 A 4 of 



