It sublimes in needle shaped crystals, or sometimes, if too quickly heated, in drops, at 169° C.; melts at 221° C., finally darkening and carbonizing.
Its bitter taste is its most prominent physical characteristic. I have verified the statement that one grain of strychnia in a gallon (70,000 grains) of water is distinctly perceptible. One grain in 30,000 is markedly bitter.
Its salts are crystallizable, and also bitter, lævo-rotatory in solution, mostly colourless, neutral to test-paper, generally soluble with facility in water, hence more rapidly poisonous than the free alkaloid. _Strychnia sulphates_ occur in large four-sided prisms, octahedrons, or needles, according to the amount of water of crystallization. _Strychnia nitrate_ crystallizes in silky needles, easily soluble in water. The _sulphate_ is officinal in the French, the _nitrate_ in the German, Austrian, Swiss, Norwegian, and Dutch Pharmacopœias. The acetate and hydrochloride are met with in commerce, but are not officinal. _Strychnia_ itself, the free alkaloid, is prescribed in the British Pharmacopœia. _Liquor strychniæ_ is a solution of the hydrochloride.
_Separation._—Strychnia is probably the easiest of the alkaloids to detect, on account of its stability and the delicacy of its reactions. One half-millionth of a grain in the pure state is discoverable by the colour tests (Pharm. Journ., July, 1856). Putrefaction does not change it, for Richter detected it in tissues after _eleven years_ (Sammlung Klin. Vorträge, 69, 562), and other observers in decomposed or buried bodies after five to eight weeks. And yet there are few analysts who have not on some occasion failed to find it (see p. 147.) A very small quantity, about a grain, may destroy life. Even of this, only a portion is absorbed; the rest is eliminated by vomiting (when it occurs), and by the urine and fæces; the absorbed portion is diffused with great rapidity through a large mass of blood and tissue; the result is that we are looking for _one part_ of the poison in about a _million times_ its weight of impurities—almost worse than the needle in the haystack. Matters are still more difficult if the theory be true that an alkaloid, in killing, itself suffers change (see pp. 128 and 133)—an idea that Dr. Letheby and Mr. Nunneley strongly repudiated in the Palmer defence, though the latter witness had to admit that he himself had once failed to detect strychnia in an animal to which he had administered it. Dragendorff records several negative results without apparent cause. Taylor (Med. Jur., 1873, Vol. I., 414) mentions cases of non-discovery by Dr. Reese of Philadelphia, Mr. Horsley of Cheltenham, by himself in the organs of an animal hypodermically poisoned; and also a case in which _five grains_ had been taken, and only a little over a grain was found. Sonnenschein (Casper’s Handbook) in one case found a quantity in the stomach, but none in the tissues; yet it had caused death. All these facts greatly support the theory that the alkaloid is itself changed in causing death.