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the compounds of chromium. 
Green oxide 8-024 or 30-02 or 6 atoms. 
Chromic acid 1-7369 or 6-5 1 atom. 
Water - - 2-2391 or 8-38 7~ atoms. 
From the preceding analysis it appears, that brown oxide 
of chromium is a compound of 1 atom chromic acid and 6 
atoms green oxide. The combination is not very intimate, 
since the chromic acid is gradually separated by water. It 
is not capable of combining either with acids or alkalies, or of 
forming peculiar compounds. When it is digested in acids, 
the common salts of green oxide of chromium are obtained. 
To alkaline solutions it gives out chromic acid, while green 
oxide of chromium remains. 
In my “ First Principles of Chemistry/' vol. ii. p. 54, I 
mention that I formed a combination of brown oxide of 
chromium and soda, and I describe the process followed. I 
merely inferred the existence of brown oxide in this liquid, 
from its colour. I have since analyzed it, and found it a 
mixture of nitrate of soda and chromate of chromium. When 
nitric acid is digested on green oxide of chromium, and the 
liquid after being evaporated to dryness is fuzed in a crucible, 
the nitric acid is destroyed, and abundance of chromic acid 
formed. By this process, if we stop in time, we may form a 
brown-coloured liquid, which, when evaporated to dryness, 
leaves a substance quite similar in its properties to brown 
oxide of chromium. 
From the preceding investigation it follows, that chromium 
combines with two proportions of oxygen, forming green 
oxide and chromic acid. The atomic weights and consti- 
tuents of chromium and its oxides are as follows : 
