196 
Dr. Thomson on some of 
The liquid thus deprived of green oxide, and perfectly 
neutral, was mixed with a solution of nitrate of barytes, as 
long as any precipitate continued to fall. By this process 
the liquid was deprived of its yellow colour, the chromic acid 
having fallen in the state of chromate of barytes. This 
method of separating chromic acid does not succeed unless 
care be taken to leave no excess of acid in the liquid ; for 
chromate of barytes dissolves easily in even dilute acids. If 
this inadvertency has been committed, the best way is to pour 
caustic ammonia into the liquid till you have supersaturated 
the acid. This will throw down all the chromate of barytes, 
previously held in solution, without acting upon nitrate of 
barytes, should an excess of that salt have been introduced. 
The chromate of barytes thus obtained being washed, dried, 
and ignited, weighed 148*37 grains. Chromate of barytes is 
a compound of 
1 atom chromic acid - - 6*5 
1 atom barytes - - 9*75 
16*25 
148*37 grains of the salt therefore contain 59*34 grains of 
chromic acid. 
The residual liquid thus freed from chromic acid was pre- 
cipitated by nitrate of silver. The chloride of silver obtained, 
weighed, after being washed, dried, and fused, 164*42 grains, 
equivalent to 40*54 grains of chlorine. 
Thus the constituents obtained from 90* 1 gr. of the red 
liquid were 
