225 
the compounds of chromium. 
water. When heated, the colour becomes red, and it remains 
so, though with a stronger tint of yellow after the salt has 
become cold. In a strong red heat it fuses and effervesces, 
as if a gas were making its escape. The colour becomes 
brown, and the salt is no longer completely soluble in water. 
To determine the composition of this salt, 190 grains of 
bichromate of potash were dissolved in water, and a quantity 
of magnesia alba, which contained 25 grains of magnesia, 
was digested in the liquid till the whole was dissolved. The 
colour of the solution was now a fine yellow, and no more 
magnesia would dissolve in it. The liquid being evaporated 
to dryness, the potash-chromate of magnesia obtained weighed 
244*4 grains. Its constituents were obviously 
Chromic acid - 
130 
or 13 
2 atoms. 
Potash - - 
60 
or 
6 
1 atom. 
Magnesia - - 
25 
or 
25 
1 atom. 
Water - - 
29 4 or 
2*94 
2i atoms 
In another experiment the quantity of water was only 
2*12 grains. We may therefore consider the salt as com¬ 
posed of 
2 atoms chromic acid 
- 13 
1 atom potash 
- 6 
1 atom magnesia - 
- - 2*5 
2 atoms water 
- 2-25 
23*75 
This salt is a compound of 1 atom chromate of potash and 
^ atom chromate of magnesia, containing the usual quantity 
of water of crystallization. 
Gg 
MDCCCXXVII. 
