j. gave on drying 2.7 of solid residue, or 1 grain in about 22.2 minims. Tincture of opium made with good Turkey opium, previously dried and reduced to powder (Pharmacopœia directions) fl.
j. gave on drying—three experiments—3.1, or 1 grain of residue in 19.3 minims.
If made with opium capable of being reduced to a state of powder, the average quantity of extract would be about 1 grain in 20 minims; this proportion would indicate that one-third of the solid ingredient (opium) is left undissolved, which was found by Mr. Phillips to be the case. I believe all good specimens of Turkey opium yield about this amount of residue. An experiment made within the last week at Mr. Bell’s establishment gave this result. If then the strength of tincture of opium be considered to be that indicated by Mr. Phillips, we must assume that the undissolved portion possesses the same therapeutic effects as the dissolved portion. Is this correct?
It has been stated by some that morphia can be extracted from the residuum, and in Dr. Pereira’s Materia Medica, we find the following observations: “Proof spirit dissolves the same constituents as water does, but it takes up a larger proportion of narcotine, resin, oil. I have repeatedly prepared morphia from the insoluble residue left behind in the preparation of the tincture.” Again, in Dr. Thomson’s Dispensatory it is stated that Mr. Brande finds that the whole of the morphia is not taken up; but is found in no inconsiderable quantity in the filter. {87} We suspect occasionally narcotine has been taken for morphia,[7] and in the cases where morphia has really been found, unless the residue had been previously washed, an error may have arisen from the alkaloid being contained in the tincture of opium adhering to the dregs, and not from any contained in the residue itself. I have recently endeavoured to ascertain the true state of the case, and chiefly by means of a therapeutic inquiry into the strength of the residuum. The residue of tincture of opium prepared in the ordinary way at University College Hospital, was taken for experiment; it was first washed with a little cold water to remove any adhering tincture, and afterwards dried in a water-bath. By digestion with ether, it was found to yield abundance of narcotine, and was also found to contain meconic acid sufficient to strike a claret color with the persalts of iron; but at the same time nitric acid gave no evidence of the presence of morphia. It was found also by experiment that proof spirit at the ordinary temperature dissolved but a very small portion of narcotine; the bulk of the narcotine therefore remains in the residuum from the tincture of opium, perhaps united with meconic acid; for when treated with water acidulated with acetic acid, both narcotine and meconic acid were dissolved.
[7] In the sixth edition of Dr. Thomson’s Dispensatory, page 1061, the following method is given for obtaining “meconate of morphia,” extracted from the Quarterly Journal of Science, vol. xx., from which it will be at once observed, that narcotine was mistaken for crystallized meconate of morphia.
“Reduce good opium to powder, put it into a paper filter, add distilled water to it, and slightly agitate it; and in this way wash it till the water passes through colorless, after which, pass a little diluted alcohol through it; dry the insoluble portion (now diminished to one-half,) in a dark place; digest it, when dry, in strong alcohol for a few minutes, applying heat; separate this solution, which by boiling, and after evaporation, will yield crystallized meconate of morphia of a pale straw color.”
A portion of the residue was given internally; one grain to a healthy adult produced no effect; two grains were given with no result; the dose was then successively increased to four grains then to six grains, afterwards to thirteen, and lastly to thirty grains, without causing the slightest effect on the individuals to whom it was administered; the only limitation to the quantity given being the unpleasantness of taking so large an {88} amount of so bulky a matter. It appears, therefore, that the residue is, to all intents and purposes, inert.
From these experiments, it is evident that even should traces of morphia be contained in the dregs, still the quantity must be such (when the tincture is prepared according to the London Pharmacopœia) as to make no appreciable diminution of the strength of the preparation, and that the tinctura opii contains the active matter of the whole of the drug used in its formation, and therefore about 12 minims of tincture of opium possesses all the activity of 1 grain of crude opium, assuming that it loses only 12 per cent. in the drying. If dry opium is taken for comparison, 1 grain is contained in about 131⁄2 minims; and, therefore, one fluid drachm of tinctura opii contains about 5 grains of the drug, or 41⁄2 grains (according as it is compared with the dry or moist opium), in place of 3 grains; or 1 fluid ounce contains 40 or 36 grains in place of 24 grains usually assumed to be contained in it: a difference of strength of the highest importance when we consider the highly poisonous and powerful therapeutic action of the drug.
In the Edinburgh preparation the amount of tincture containing a grain of opium is about 131⁄2 minims, for the opium is ordered in the same proportion but not previously reduced to powder or dried. In the Dublin preparation the opium is ordered to be coarsely powdered, but avoirdupois weight is used in place of apothecaries, which makes the strength of the tincture such that 12.75 minims contain one grain.