When the purified poisonous material (p. 32) was extracted with 50 per
cent. alcohol, only a small quantity was dissolved as was stated above.
The insoluble residue was treated with fuming nitric acid. Violent
reaction took place at once with copious evolution of red fumes and
heat. When the reaction was over, a sticky red gummy mass was left which
was slightly soluble in cold water and readily soluble in warm alcohol.
The water extract was yellow, and the alcoholic solution was red. That
the water extract contained picric acid was shown by the following
experiments:
(1) A portion was gently warmed with a few drops of a strong
solution of potassium cyanide and two drops of sodium
hydroxide. The red color of potassium isopurpurate was
formed.
(2) A portion of the water solution was heated with glucose
and a few drops of sodium hydroxide. The deep red color of
picraminic acid was produced.
(3) A few drops of an ammoniacal solution of copper sulphate
was added to the water extract. A yellow-green precipitate
was formed.
(4) The water extract dyed silk, but did not dye cotton
cloth.