Tests.—Strychnia is a white crystalline solid, very insoluble in water, soluble in alcohol or chloroform or weak acids, and having an intensely bitter taste.
1. Pure strychnia is not changed in color when treated with iodic acid or with either of the strong mineral acids; but as this alkaloid generally contains brucia, nitric acid reddens it.
2. Dissolved in sulphuric acid no change ensues; but on adding a fragment of bichromate of potass to the solution a series of blue, violet, purple and red tints are produced. The same result is brought about by using ferricyanide of potassium, permanganate of potassium, the peroxide of lead, or the black oxide of manganese.
3. If the skin of a frog be dried, and a few drops of a solution containing strychnia applied to it, strong tetanic convulsions will ensue, and be reproduced every time the animal is touched or irritated. According to Dr. Marshall Hall this strychnoscopic test will detect the 1⁄5000th of a grain, or even less.
4. An exceedingly useful class of tests for many poisons has been introduced by Dr. Guy; we mean the crystalline appearances presented on subliming the substance and condensing it on a cool microscopic slide, or the crystalline form observed as modified by various reagents. Thus the strychnine sublimate, touched with a drop of carbazotic acid, forms groups of arborescent crystals, each branch forming part of a circle, when seen under the microscope.