On the detection of strychnia as a poison : and the influence of morphia in disguising the usual colour-test / by John J. Reese.

  • Reese, John J. (John James), 1818-1892.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: On the detection of strychnia as a poison : and the influence of morphia in disguising the usual colour-test / by John J. Reese. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    discovered only when it is in the pure state, and free from all other organic admixture. Of course it would be in vain to attempt to detect anything like such infinitesimal portions in mixtures like the contents of a stomach. But as I have already shown, there is no difficulty of discovering as small a quantity as the one-hundredth of a grain (and doubtless even less), when diffused in a pint of complex organic mixture. I will add a few words in relation to the best mode of proceeding, when we desire to test for extremely minute portions of pure strychnia. A solution is first made of any given quantity—say one-tenth of a grain in a fluidounce of distilled water, with a few drops of acetic acid to insure solution. The number of drops contained in the portion of liquid is to be ascertained by means of a pipette, prepared by drawing out a glass tube to a fine point. The solution may then be diluted to any degree required. One drop of the liquid, representing the ascertained fractional part of a grain, is then to be placed upon a small, perfectly clean white porcelain capsule; and evaporated to dryness, either in the sun or by a very gentle heat. When cold, a drop of pure sulphuric acid is to be placed, by means of a glass rod, on the capsule alongside of the dry spot, but not in contact with it. Next, a small crystal of bichromate of potassa (or, preferably, of ferricyanide of potassium) is to be laid on the dish ; after which, a clean, dry and finely-pointed glass rod should be drawn through the drop of acid so as to bring a very little of it in contact with the spot; the little crystal is next to be moved by the rod once or twice over the moistened spot, when there will immediately appear, flashing out, as it were, the characteristic blue colour—more or less transient, according to the amount of the alkaloid present, and passing through the usual tints. It may appear to some that I have been unnecessarily minute in describing the details of what seems a very simple experiment; but I can assure such that a successful result can only be obtained, when operating upon such extremely small quantities, by the strictest attention to these details. For example, too high a temperature in the evaporation may decompose the minute quantity of strychnia, which, however, must be perfectly dry ; again, the sulphuric acid should be pure and strong ; for this purpose the drop should be taken by means of a glass rod out of the bottle, and not dropped from its rim, as it would, in the latter case, be apt to have become some- what diluted from moisture absorbed from the atmosphere. Again, the fragment of the crystal used should be very small—one or two lines in dimensions; it should be free from all adherent powder, so as not too soon to dissolve in the acid, and thereby conceal the true colour. For this reason I decidedly prefer the ferricyanide to the bichromate, when manipu- lating with very minute portions of strychnia : it is much less apt to colour the acid. Lastly, the experimenter must avoid using too much acid; hence the direction to draw only a portion of the drop over the strychnia spot, by means of a pointed glass rod. By carefully observing the above direc-