TOXICOHÆMIC,
SNAKE POISONS, ETC.
Under this head may be classed all those effects produced by the sting or bite of various insects and reptiles, and also by the bite of the mad dog and wolf.
No medico-legal question is likely to be raised on this subject, at least in this country, where, with the exception of the common viper or adder, all our reptiles are harmless enough.
CHAPTER VII
THE VEGETABLE ALKALOIDS
Vegetable alkaloids may be classified in three groups: (1) derivatives of pyridine, e.g. atropine, conine; (2) derivatives of quinoline, e.g. cinchonine, narcotine; (3) substituted amines and amides. The majority of the vegetable alkaloids belong to the first two groups. They are for the most part solid, crystalline, and colourless; a few, such as conine, nicotine, and pilocarpin, are liquid. They combine with acids to form salts, and the salts are more soluble in water than the free alkaloid. Alkaloids possess certain properties in common, amongst which is that of being precipitated from their solutions by certain reagents, which are called alkaloidal grouping reagents. Some are precipitated by all the group reagents, others only by a few.
Alkaloidal Group Reagents
1. Iodine dissolved in solution of Potassium Iodide—Wagner‘s reagent.—Gives a reddish-brown precipitate with most alkaloids.
2. Phosphomolybdic Acid—Sonnenschein‘s reagent.—Made by dissolving phosphomolybdate of soda in water containing one-tenth its volume of strong nitric acid. It gives a yellow precipitate with most of the alkaloids; it also precipitates ammonium salts and ammonia derivatives, also salts of lead, silver, and mercury unless there be sufficient acid to keep them in solution.
3. Potassio-mercuric Iodide—Mayer‘s reagent.—Made by adding a solution of potassium iodide to one of mercuric chloride until the red precipitate first formed be just dissolved. This solution precipitates most of the alkaloids. The solution to be tested must contain acetic acid.