184 Dr. Thomson on some of 
a red heat : it was then brought into fusion, and kept in that 
state for about 20 minutes. The fuzed mass on cooling had 
a fine yellow colour. Being digested in water a dirty brown 
matter remained, weighing when dried on the filter 1-89 
grain. When ignited it became green, but did not glow, and 
the weight was reduced to 1*19 grain. Thus 11 *8 grains of 
green oxide were converted into chromic acid. The potash 
solution treated as before gave 49*21 grains of chromate of 
lead, equivalent to 15*603 grains of chromic acid. Thus, 
11*8 grains of green oxide became 15*603 chromic acid. 
According to this experiment, we have chromic acid com- 
posed of Protoxide n*8 or 4*654 or 4 915 
Oxygen 3*803 or 1*5 or 1*585 
15*603 6*154 6*5 
These experiments all deviate a good deal from the truth. 
The mean of the three gives us the constituents of chromic 
acid, as follows : 
Protoxide - - 4*957 
Oxygen - - i *543 
This gives us 4*957 for the atomic weight of green oxide. 
The deviation from the truth does not amount to 1 per cent. 
I expected by this mode of experimenting to have obtained 
much more satisfactory results. 
3. A quantity of liquid chromic acid was evaporated to 
dryness, forming, as usual, a very deliquescent red mass, 
which I found by analysis to consist of 
Pure anhydrous chromic acid - 88*97 
Protoxide of chromium - - 4 30 
Water - 6* 73 
100*00 
