74 
Selected Articles. 
precipitated with the oxide of chrome, and may be separated 
from it afterwards by calcining them with potash. To se- 
parate iron from chrome when they are both in solution in 
an acid, all that is required is to saturate the fluid with hy- 
drosulphuric acid, to bring the iron to the state of a deutoxide, 
when the oxide of chrome alone will be precipitated by the 
carbonate of barytes. 
The oxide and oxidule of mercury dissolved in nitric acid, 
are precipitated like the oxide of bismuth by carbonate of 
barytes. This means may be employed to separate this me- 
tal from those which, like it, are precipitated by hydrosul- 
phuric acid. 
It has heretofore been proposed to separate the different 
oxides by means of the carbonates of the alkaline earths, 
without this idea having received the attention it deserved ; 
but the reason why this method obtained so little favour, is 
that the important point of the temperature at the time of 
precipitation had not been adverted to. The action of these 
salts differs with different temperatures ; thus the chlorides or 
nitrates of cobalt, nickel, manganese, zinc and copper are 
completely decomposed by the carbonates of lime, barytes 
and magnesia, but only at a temperature above 60°. Cop- 
per and zinc are the first precipitated, cobalt and nickel next, 
and manganese the last; but this circumstance cannot be 
taken advantage of to separate these metals from each other. 
Journ. de Pharm, 
