The dose should depend upon its molecular state. Thus, if it be very dry and likely to become caked together in the stomach, very large doses may not act at all, or may cause irritation, while if moistened or formed into hydrate, or carefully mixed with some other fine powder, moderate doses will give a much better result. Thus, Quesneville took 80 grammes without much advantage, but afterward using the drug thoroughly soaked in water, soon obtained good effects with 5 to 10 grammes; his "bismuth-cream" is a valuable preparation, better known abroad than in this country. Doses of 1 1/2 to 2 1/2 dr. are now seldom used, 5 or 10 gr. representing an average prescription for adults. Much more may, however, be given in organic disease when there is erosion or ulceration of the alimentary surface; milk or almond emulsion is a good vehicle. The subnitrate forms a part of the "poudre de Wendt," also of the powder of Robert Thomas; combined with magnesia it is "Patterson's, or American powder," and with pepsin, the "poudre de Royer."

The liquor bismuthi et ammoniae citratis is miscible with water and spirit, but not with alkalies without precipitation. The so-called "lac bismuthi" (Symes) contains the hydrate mechanically suspended.

A lactate, a tannate, and a valerianate of bismuth have been described: the first is a soluble salt, and may be given in small doses; the compound with tannin is designed to favor its astringent, and the valerianate any nerve-tonic powers. A citrate of iron and bismuth is sometimes useful.

Besides these, there are many private preparations, as of bismuth and pepsin, bismuth and strychnia, etc.

A glycerole of the neutral nitrate is best prepared by dissolving 1/2 oz.

of the crystallized salt in 2 dr. of pure glycerin and an equal quantity of distilled water, afterward adding glycerin to 6 oz. Ungueutum bismuthi may be prepared with 1/2 to 1 dr. of any bismuth salt in 1 oz. of cold cream (not benzoated). An oleate is made with oleic acid and the oxide in strengths of from 10 to 20 per cent. A lotion or injection is made with 1 part to 8 of liquid. Pessaries are made containing 15 gr. in each.

[Preparations, U. S. P. - Bismuthum, Bismuthi subcarbonas, and Bismuthi subnitras.]

Adulterations

Besides being variable in its chemical constitution, in the amount of oxide and of acid present, the subnitrate may contain added carbonate, and phosphate of lime, carbonate of lead, subchloride of bismuth, and other metals introduced in the process of manufacture, also certain natural impurities not removed - e.g., traces of iron, copper, silver, and arsenic. The last is the most important, although no official test for its presence in bismuth is given. In the older preparations it was probably always present, and, so long ago as 1743, Geoffrey expressed his fear of bad results from it ("Materia Medica"). In later times, Dr. Taylor found it in three out of five specimens; and Mr. Edin found it in many specimens of liquor bismuthi when it was first introduced (Pharmaceutical Journal, 1868).

The practical bearing of such adulteration was illustrated in a trial for arsenical poisoning at Philadelphia about twenty years ago. It was proved that bismuth "nitrate" had been prescribed shortly before death: a specimen of the particular salt dispensed could not be found, but, of ten others purchased in the city, a majority contained arsenic, and although the irritant symptoms had commenced before bismuth was prescribed, and the proportion of arsenic found in the viscera was much more than bismuth adulteration would account for, yet the trial was stopped, and the accused person discharged (American Medical Journal, July, 1858).

At the present time, however, adulteration with arsenic is exceptional. Of six chance specimens examined under the direction of Dr. Anstie, not one contained it (Practitioner, 1871); and Professor Siebold, after much experience, reports that it is now rarely found (Pharmaceutical Journal, December, 1875). Of seven samples of the basic nitrate of the United States Pharmacopoeia, one only contained arsenic - .33 per cent. (Op. cit., November, 1875). In the oxide he often found traces of sodium and lead, and commonly subchloride and subnitrate.

Selenium and tellurium have been found in some specimens of bismuth salts, and a Colorado ore of the metalloid has been found to contain 34 per cent. of tellurium. This may explain the offensive alliaceous odor which is sometimes given to the breath by special samples of bismuth preparations. It resembles that of arseniuretted hydrogen, and has naturally been attributed to that gas, and yet not correctly; and the absence of the poison in certain offending samples has been proved by analysis

(Pharmaceutical Journal, December, 1875); neither can the odor be traced to prussic acid or other usual ingredients in bismuth mixtures: while we know that tellurium can impart an offensive odor, for Sir James Simpson made trial of the drug, and Dr. Maclagan relates that on one occasion a student took a dose which obliged him to sit apart from the class for the rest of a session! (Edinburgh Medical Journal, December, 1854).

The carbonate of bismuth is liable to contain chlorides, also sodium, and sometimes lead. In five specimens examined by Prescott no arsenic was found (Pharmaceutical Journal).