Mz C. Lea on Picric Acid. 181 
No precipitate, solution very 
nearly colorless, faintest tinge 
sible, 
of yellow only vi 
I vol. sol. picric nie E dilute sul- 
phuric acid, same dilu 
2 vols. solution picric _ 1 vol.) Nearly the whole of the picric 
sulphuric acid, same dilutio cid was precipitated. 
The amount remaining in solution continued in further trials to 
diminish s as the sulphuric acid became more dilute, until a max- 
imum was reached with 
vols. solution picric acid, 1 vol. 
hie sulphuric acid, same di lation. 
It thus appears that eee of sulphuric acid and water reach 
their minimum of solvent power for picric acid when the mix- 
ture consists of about 1 vol. acid to 11 vols. water. The propor- 
¢ acid of a certain age without in any way decomposi ng 
the acid, is very remarkable. Four volumes of sulphuric aci 
te ith 
panic acid dissolves in such a mixture to a utio on. 
18 peculiar property has no doubt led to ie supposition of 
the insolubility of picnic acid in sulphuric acid above referred to. 
ater containing 3. ly, of picric acid exhibits a bright yel- 
low color. With sua.ssx the color is still distinct, even ina 
stratum of not over an inch in thickness. But in large quanti- 
ties a millionth gives a distinct color as above mentioned. 
Tests for Picric Acid. 
The best tests for picric acid are 
Semanstal solution of sulphate of copper, which gives a 
greenish crystalline precipita 
ilatine su oikee Lie ith pened of alkali, which with heat gives 
a oe red lig 
Ikaline ee with ammonia, which when heated gives also : 
a ise uid. 
The eee table will exhibit the relative sensibility. of 
reagents 
