M. C. Lea on Picric Acid. 183 
remain in the mother water. A moderate but decided excess 
of acid is absolutely necessary, because otherwise a portion of 
alcaline picrate escapes decomposition. Even then, it is advis- 
able to recrystallize the acid from alcohol. If picric acid be 
dissolved by the aid of heat in a solution of sulphate, nitrate, 
or almost any salt of potash, more or less picrate of potash will 
crystallize out on cooling. I have thought this process not 
devoid of interest, because picrie must become more extensively 
known in the laboratory and in the arts than hitherto. 
Effect of Reducing Agents. 
The effects of reducing agents when alkali is not present, or 
not present in excess, (in presence of excess of alkali, picramic 
acid is formed), are very variable, depending upon slight differ- 
ences which it is very difficult to seize. I subjoin some of the 
best marked results obtained. 
A mixture of picric acid, alcohol, iron filings, and acetic acid, 
were digested for an hour at a heat a little below 212°. The 
filtrate was intensely blue, by standing for half an hour or less, 
became brown and muddy, depositing a blackish powder, in 
small quantity, and without trace of crystallization. This filtrate 
was not changed in color by acids, or apparently affected b 
them. Alkalies decolorized it. Its shade of blue varied consid- 
erably in different experiments, sometimes full blue, sometimes 
violet, sometimes greenish. ‘ 
Other experiments were made by acting on picric acid by zine 
and dilute sulphuric acid. After an action of some hours, the 
solution was mixed with alcohol and filtered. The filtrate heated 
with bicarbonate of potash in successive portions, gave a fine 
Violet liquid, which with further addition of alkali became deep 
ue with a tinge of violet. According as acid or alkali were 
gee in excess there was more of the violet or blue shade, 
e colors were always very fugitive, and changed to dirty brown 
by standing, with deposit of an amo hous blackish pow des, 
(very small in quantity compared with the picric ac _used,) 
which was soluble in acids, and insoluble in alcalies. : 
hese experiments although many times repeated did not lead 
to the isolation of any substance of interest. There is a certain 
in picric aci 
Philadelphia, April, 1961. 
contains the radical C,,H, which exists in a substituted form 
d. 
