Researches on strychnine / by I. L. Crawcour.

  • Crawcour, Isaac Lionel, 1825-1886.
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: Researches on strychnine / by I. L. Crawcour. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    strument—this was evaporated to dryness on a water bath ; when cold, a minute drop of strong sulphuric acid was placed in the centre of the plate, and a small portion of powdered bichromate of potash taken up on a finely pointed glass rod; by moving this about in the acid and running the rod over the plate, lines of an intense blue, rapidly changing into red, were produced whenever the rod came in contact with the strychnia. In experimenting upon these minute quantities, two things are necessary, first that the strychnia shall be perfectly dry, (the minutest quantity of moisture defeats the experiment), and secondly, that the heat shall be most care- fully applied, as otherwise decomposition of the alkaloid ensues, and the test is of no avail. I have little doubt that by a moderate amount of pa- tience and care in manipulation, the hundred thousandth of a grain of strychnia might be discovered by this test. I must be understood, how- ever, to refer to strychnine wholly unmixed with any other salt, or organic matter. We are simply now examining the limits of defining power. So easily is strychnine detected, that if a drop of water containing the thou- sandth part of a grain be allowed to dry on a glass slide, a large space will be found covered with crystals, forming a most beautiful microscopic ob- ject, and the forty thousandth of a grain is distinctly visible to the naked eye. Much has been said, and I think without any show of reason as to the fallacy of colored tests, but the fact is that both in inorganic and in organic analysis, we depend entirely upon the color of precipitates for the detection of substances. No one has yet questioned the fact, that, if on adding the ferrocyanide of potassium to a colorless solution we get a blue precipitate, iron must undoubtedly be present, or if a red color be produced by addi- tion of perchloride of iron, which color is not destroyed by solution of cor- rosive sublimate, a salt of opium is present. The tests for copper, arsenic, bismuth, hydro-cyanic acid, iodine, and a host of others, all depend upon the peculiar colors, produced by the action of re-agents, and no one has yet questioned their accuracy, and I consider the peculiar blue, produced by bichromate of potassa and sulphuric acid, on a salt of strychnia, to be as fully distinctive as any of the above. The fact is, that in medico-legal investigations, we must not be satisfied by any one test—but each must be rendered corroborative of the other. No one would positively swear to the presence of arsenic, from the yellow precipitate produced by the ammonio- nitrate of silver, but if the same solution should in addition give a green color, with ammonio-nitrate of copper, I question whether we should have any doubt of the presence of the poison. In like manner, if we have a