Mercury, in its metallic state, is never applied to any medical use,[[522]] except in visceral obstruction, in hopes of forcing a passage by its gravity; but under various forms of preparation, it affords a series of very active remedies. Adulterations. With the exception of Peruvian Bark, there is perhaps no active article in the materia medica more shamefully adulterated; its impurity is at once indicated by its dull aspect; by its tarnishing, and becoming covered with a grey film; by its diminished mobility, in consequence of which its globules are unable to retain the spherical form, and therefore tail, as it is technically expressed. Lead is discovered by dissolving it in nitric acid, and adding to the solution water impregnated with sulphuretted hydrogen, when, if lead be present, a dark brown precipitate will ensue. Bismuth, by pouring the nitric solution into distilled water, when it will appear as a white precipitate. Zinc, by exposing the mercury to heat. Tin is detected by a dilute solution of nitro-muriate of gold, which throws down a purple precipitate. The presence of lead in mercury is a most dangerous circumstance; I have once witnessed a case of cholica pictonum in consequence of it. The usual mode of purifying quicksilver, by pressing it through chamois leather, will not separate the lead, if it be, as is generally the case, in combination with bismuth; for the manner in which the adulteration is effected, is by melting with a gentle heat these two metals, and adding the alloy to the mercury; and although this alloy should exceed one-fourth of the whole bulk, it will pass, together with the mercury, through chamois leather. On standing, the bismuth will be thrown upon the surface, in the form of a dark powder, but the lead will remain in solution. The greatest part of the mercury of commerce comes from Istria and Friuli, and from the Palatinate, and as it passes through the hands of the Dutch, we must expect to receive it in a state of alloy. On a superficial examination, it ought not, when shaken with water, to impart to it any colour; when agitated or digested with vinegar, it should not communicate a sweetish taste; and when exposed in an iron spoon to heat, it ought to evaporate entirely. The French are so well aware of the mischievous extent to which this metal is falsified, that in their late Codex they direct the reduction of the red oxyd in order to obtain it; the process however is too expensive for general adoption. The Italian Jews purify quicksilver for their barometers, by digesting it in dilute sulphuric acid, which is by no means an improper process. The mode directed for the purification of mercury by the London College, (Hydrargyrum Purificatum) is unable to separate it completely from its more deleterious contaminations. It is a general opinion in Germany, that mercury, boiled in water, will impart to it an anthelmintic virtue;[[523]] this, if it happens, can only depend upon the impurities of the mercury; but large draughts of cold water are in themselves anthelmintic. Although metallic mercury in its fluid form exerts no effect upon the animal system, it, nevertheless, in a state of vapour, manifests considerable powers; and it is necessary for the practitioner to be informed that it assumes this condition at the ordinary temperature of the atmosphere. I have stated several experiments in proof of this fact in my work on Medical Jurisprudence, Art. “Aerial Poisons,” to which the reader may refer.
HYDRARGYRUM PRÆCIPITATUM ALBUM. L.
Sub-murias Hydrargyri Ammoniatum. D.
White Precipitate.
Qualities. Form, an impalpable powder of a snowy whiteness; Odour and Taste, none. Chemical Composition. It is a triple compound of oxide of mercury 81, muriatic acid 16, ammonia 3 parts. Solubility. It is insoluble in water, and in alcohol; when triturated with lime water it does not become black. It is now only used in combination with lard as an ointment; formerly it was administered internally, and Boerhaave strongly recommends it as a safe and mild mercurial, and as seldom, if ever, exciting copious salivation. Officinal Prep. Unguent. Hydrarg. præcipitati albi. L.D.
HYDRARGYRUM CUM CRETA. L.D.
Mercury with Chalk.
This is mercury slightly oxydized by trituration, and mixed with chalk. Grs. iij contain about one grain of mercury. Dose, grs. v to ʒss. It is a mild and excellent mercurial, and has been known to cure syphilitic affections, when the constitution had proved rebellious to every other form of preparation. Dr. George Fordyce committed a great error, when he denied to this compound any mercurial efficacy. The peculiar mildness of this preparation has been very justly attributed to the effects of the carbonate of lime, in neutralizing acid matter in the primæ viæ. In Mesenteric affections I have employed it with much advantage; in certain forms of Dysentery it is also a very valuable medicine.
HYDRARGYRI NITRICO-OXYDUM. L.
Oxydum Hydrargyri rubrum per acidum Nitricum. E.