Note 371 — PART VI.—ALKALOIDS AND POISONOUS VEGETABLE PRINCIPLES SEPARATED FOR THE MOST PART BY ALCOHOLIC SOLVENTS. (continued 2)

Other methods of opium assay have been published: see Mr. A. B. Prescott’s method (Proceedings of Amer. Pharm. Assoc., 1878); Allen (Commercial Org. Analysis, vol. ii. p. 473); E. R. Squibb’s modification of Flückiger’s method (Pharm. Journ. (3), xii. p. 724); a rapid mode of opium assay, MM. Portes and Lanjlois (Journ. de Pharm. et de Chim., Nov. 1881); Year Book of Pharmacy, 1882.

To the above may be added—(1.) Schacht’s Method.—5 to 10 grms. of dry, finely-powdered opium are digested with sufficient distilled water to make a thin pulp. After twenty-four hours the whole is thrown on a weighed filter, and washed until the washings are almost colourless and tasteless. The portion insoluble in water is dried at 100° and weighed; in good opium this should not exceed 40 per cent. The filtrate is evaporated until it is about one-fifth of the weight of the opium taken originally; cooled, filtered, and treated with pure animal charcoal, until the dark brown colour is changed into a brownish-yellow. The liquid is then refiltered, precipitated with a slight excess of ammonia, allowed to stand in an open vessel until all odour of ammonia disappears, and at the same time frequently stirred, in order that the precipitate may not become crystalline—a form which is always more difficult to purify. The precipitate is now collected on a tared filter, washed, dried, and weighed. With an opium containing 10 per cent. of morphine, its weight is usually 14 per cent. A portion of the precipitate is then detached from the filter, weighed, and exhausted, first with ether, and afterwards with boiling alcohol (0·81 specific gravity). Being thus purified from narcotine, and containing a little colouring-matter only, it may now be dried and weighed, and the amount of morphine calculated, on the whole, from the data obtained.

(2.) Fleury has proposed a titration by oxalic acid as follows:—2 grms. of the powdered opium are macerated a few hours with 8 c.c. of aqueous oxalate of ammonia, brought on a filter, and washed with 5 c.c. of water. To the filtrate an equal volume of 80 per cent. alcohol and ammonia to alkaline reaction is added; and, after standing twenty-four hours in a closed flask, it is filtered, and the flask rinsed out with some c.c. of 40 per cent. alcohol. The filter, with its contents, after drying, is placed in the same flask (which should not be cleansed), a few drops of alcoholic logwood solution are added, with an excess of oxalic acid solution of known strength, the whole being made up to 100 c.c. This is divided into two parts, and the excess of acid titrated back with diluted soda-lye. If the oxalic acid solution is of the strength of 4·42 grms. to the litre, every c.c. of the oxalic acid solution which has become bound up with morphine, corresponds to 0·02 grm. of morphine.