The Precipitate per se of the older Chemists.
Qualities. Form, minute crystalline scales, of a deep red colour, inodorous, but acrid and caustic; it is soluble in several of the acids without decomposition; it is also slightly soluble in water; from which solution it is precipitated by ammonia. Uses. It is very active as a mercurial, and has been a favourite remedy with John Hunter (Form. 141) and other celebrated practitioners; it is however apt to affect the bowels, and is therefore now rarely employed except as an external application. Dose, gr. j. combined with opium gss. Adulterations. It is seldom adulterated, as it would be difficult to find a substance suited to that purpose. If well prepared it may be totally volatilized by heat.
HYDRARGYRI OXY-MURIAS. L.
Murias Hydrargyri Corrosivus. E.D.
Oxy-muriate of Mercury.
Corrosive Muriate of Mercury. Corrosive Sublimate.
Qualities. Form, a crystalline mass, composed of very small prismatic crystals, which is easily pulverized, and undergoes a slight alteration by exposure to air, becoming on its surface opaque and pulverulent. Light, however, has no effect upon it, although a different opinion has existed, and it has accordingly been recommended to be kept in black bottles. Odour, none. Taste, very acrid, with a metallic astringency, occasioning a sensation of obstruction in the throat which continues for some time. Sp. gr. 5·1398. When pulverised and thrown upon burning coals, it is immediately volatilized, giving out a thick white smoke of a very pungent smell, which irritates the mucous membranes extremely, and is highly dangerous to those who inhale it. Chemical Composition. According to the latest views, it is a Bi-chloride of mercury, consisting of one proportional of mercury, to two proportionals of chlorine. In the French codex, it is termed “Deuto-Chloruretum Hydrargyri.” Solubility. It is soluble in eleven parts of cold, and in three of boiling water, and in half its weight of alcohol; it is also very soluble in æther; indeed this latter liquid has the curious property of abstracting it from its solution in water, when agitated with it. Its solubility in water is greatly increased by the addition of a few drops of rectified spirit, or of muriatic acid. In a solution of muriate of ammonia it is seventeen times more soluble than in water, no decomposition however arises; it is therefore probable that a triple salt is formed; it is also soluble in the sulphuric, nitric, and muriatic acids, and may be obtained again unaltered, by simply evaporating the solutions. Dr. Davy, in his late researches upon corrosive sublimate states that with muriatic acid, common salt, and some other muriates, it forms definite compounds remarkable for their solubility. Its watery solution is said to change vegetable blues to green, but this is an optical fallacy, (see page 306.) On exposure to light this solution slowly undergoes decomposition; but Dr. Davy has shewn that corrosive sublimate remains unaltered when exposed in solution in media having a strong affinity for it, as in alcohol, æther, muriatic acid, &c. and that decomposition only takes place under circumstances of complicated affinities, as in the instance of Liquor Hydrargyri Oxymuriatis, and in that of the aqueous solution; in which cases Calomel and Muriatic acid appear to be formed, and oxygen to be evolved. Incompatible Substances. The carbonates of the fixed alkalies precipitate it of a yellow hue, but the precipitates are not pure oxides; ammonia forms with it a white triple compound. Lime water decomposes it more perfectly than any alkaline body, occasioning a precipitate of a deep yellow colour,[[524]] which is a per-oxyd of mercury containing a little muriatic acid; this result forms a useful lotion to ill conditioned ulcers, and has been long known under the title of Aqua Phagadenica; f℥j of lime water should be employed for the decomposition of two grains of the salt. Tartarized antimony, nitrate of silver, acetate of lead, sulphur, sulphuret of potass, and soaps, decompose it. Iron, lead, copper, bismuth, and zinc, in their metallic state, also decompose it, producing precipitates which consist of an amalgam of the metal employed, except in those cases where the metal in question refuses to amalgamate with mercury, when this latter metal appears as a metallic dew, composed of very minute globules, with calomel; hence mortars of glass or earthenware should be used for dispensing this article; when triturated with olive oil, the oil becomes white, and when boiled with it, calomel is precipitated; the same happens if sugar be substituted for oil. The volatile oils reduce it. When Oil of Turpentine was used, some traces of artificial camphor was discovered by Dr. Davy, and when the oils of Cloves and Peppermint, a purple compound distilled over, consisting of the oil employed and muriatic acid. The following vegetable infusions produce precipitates, viz. the infusions and decoctions of chamomile, horse-radish root, calumba root, catechu, cinchona, rhubarb, senna, simarouba, oak bark, tea and almond emulsion. Swediaur observes, that “many authors have recommended sublimate combined with bark, but that a reciprocal decomposition is thus produced, by which the energies of both remedies are alike annulled;” to this ignorance, however, he thinks that many patients have been indebted for their lives; for, says he, “I see every day examples of weak and very delicate persons of both sexes, to whom ignorant practitioners prescribe, and sometimes in very large doses, the corrosive sublimate, with a decoction of bark; certainly without curing the syphilis, but at the same time without occasioning those grave and dangerous symptoms, which that acrid medicine would certainly produce, if given alone, or without that decoction.” We have here presented the reader with the opinion of Swediaur; but it is just to state, that the experience of this country has rather tended to subvert, than to confirm, such a belief. That the corrosive sublimate of mercury is actually decomposed by the vegetable principles of the bark is sufficiently evident, but it would seem that the oxide thus developed, and recombined with vegetable extractive, is a very active mercurial, especially with respect to its alterative powers. The same observation will, to a certain extent, apply to the results of its decomposition by other agents; the fixed alkalies have been found by actual experiment to be incapable of disarming this salt of its virulence, because, as Orfila has stated, the oxide liberated is, in itself, an active poison. Mr. Rose has lately transmitted to me a formula for the preparation of “Alterative Drops,” which he states, from ample experience, to possess very considerable powers as a mercurial, and to excite ptyalism, with a quickness and certainty which characterize but few preparations of the same class. The principal ingredients are an alcoholic solution of corrosive sublimate and a vinous solution of tartarized antimony. It is scarcely necessary to observe that upon admixture a mutual decomposition takes place; the peroxide of mercury is precipitated by the alkaline element of the antimonial compound, whilst this latter salt, having its affinities thus overthrown, parts with the protoxide of antimony; so that the preparation holds a considerable quantity of insoluble matter in suspension, and which is to be carefully incorporated with the liquid by shaking the phial, whenever the drops are administered. Now there can be but little doubt but that the activity of this preparation is owing to the peroxide of mercury, thus diffused in a state of minute division, while at the same time the antimonial protoxide very probably disposes the stomach and system to be more readily influenced by it, for reasons which have been fully discussed in the first part of this work, p. 152. Med. Uses. It is one of the most acrid and active of all metallic preparations; in well directed doses, however, it is frequently of service in secondary syphilis, and in cases of anomalous disease, when it would be improper to administer the other forms of mercury.[[525]] In obstinate cutaneous diseases its administration in small doses is often very serviceable; I have, however, seen extreme emaciation and hectic fever produced by its too long continued exhibition, although ptyalism was never occasioned. Its application also as a lotion to leprous affections, in the proportion of about one grain to a fluid-ounce and a half of some liquid vehicle, I have frequently seen highly beneficial; in directing the use of so acrid a lotion, we should caution the patient not to touch his eyes until his hands have been washed; in consequence of a neglect of this kind I have seen a very severe ophthalmia produced. The practitioner should also remember that the system may become affected by such external applications; a case stands recorded in which a girl of five years old became salivated, and died, in consequence of an application made to the head for the cure of Tinea, which consisted of Pomatum rubbed up with a few grains of this salt. Its internal exhibition should be accompanied with mucilaginous drinks; when an overdose has been taken, the white of egg, diluted with water, is the best antidote, for Orfila has found that albumen decomposes it, reducing it to the state of mild muriate, whilst the compound which it forms with it is inert. Many examples are recorded of the success of this practice. In the Transactions of the King and Queen’s College of Physicians in Ireland, an interesting case of this kind is related by Dr. Lendrick; it is, however, at the same time but justice to state, that there are instances also of the failure of this antidote. In the 41st volume of the London Medical and Physical Journal, p. 204, the reader will find the case of a girl, who was poisoned by a drachm of Sublimate, and who, notwithstanding the copious ingestion of albumen, died in ninety hours. More recently vegetable gluten, as existing in wheat-flower, is said to answer as well as albumen; for the administration of which all that is required is to give wheat-flower and water. Dose, gr. 1/8 to ½, see Liquor Hydrargyri Oxymuriatis, and Form. 142. Adulterations. It ought to be volatilized by heat; it is frequently met with in commerce contaminated with muriate of iron, sometimes with arsenic; the presence of calomel is at once discovered from its insolubility. Tests of its Presence. If any powder be suspected to contain this salt, expose it to heat in a coated tube, as directed in the treatment of arsenic, but without any carbonaceous admixture, when corrosive sublimate, if present, will rise and line the interior surface with a shining white crust. This crust is then to be dissolved in distilled water, and assayed by the following tests; 1st, lime water will produce, if the suspected solution contains this salt, a precipitate of an orange yellow colour. 2d, a single drop of a dilute solution of sub-carbonate of potass will at first produce a white precipitate, but on a still farther addition of the test, an orange-coloured sediment will be formed. 3rd, sulphuretted water will throw down a dark coloured precipitate, which when dried and strongly heated may be volatilized without any alliaceous odour. 4th, ammonia produces a white precipitate, which is an insoluble triple salt, composed of muriatic acid, ammonia, and oxide of mercury, which, on being heated, grows yellow; it passes afterwards to a red, and gives out ammoniacal gas, nitrogen, calomel, and metallic mercury. In this operation the oxide is supposed to be decomposed by the hydrogen which results from a portion of the ammonia. 5th, Nitrate of tin, according to Dr. Bostock, is capable of detecting the three-millionth part of a grain; a single drop will occasion an immediate and copious dark-brown precipitate. All the above precipitates, if rubbed on a bright plate of copper, will render its surface very white. Where the salt is mixed with various coloured liquids, we must proceed as directed under the head of Arsenic. A very ingenious application of galvanic electricity has been also proposed by Mr. Silvester, for the detection of corrosive sublimate, which will exhibit the mercury in a metallic state. A piece of zinc or iron wire about three inches in length, is to be twice bent at right angles, so as to resemble the Greek letter Π, the two legs of this figure should be distant about the diameter of a common gold wedding ring from each other, and the two ends of the bent wire must afterwards be tied to a ring of this description. Let a plate of glass, not less than three inches square, be laid as nearly horizontal as possible, and on one side drop some sulphuric acid, diluted with about six times its weight of water, till it spreads to the size of a halfpenny. At a little distance from this, towards the other side, next drop some of the solution supposed to contain corrosive sublimate, till the edges of the two liquids become joined; and let the wire and ring, prepared as above, be laid in such a way that the wire may touch the acid, while the gold ring is in contact with the suspected liquid. If the minutest quantity of corrosive sublimate be present, the ring in a few minutes will be covered with mercury on the part which touched the fluid. This experiment may be beautifully simplified in the following manner; drop a small quantity of solution containing corrosive sublimate on a piece of gold, and bring into contact a key, or some piece of iron, so as to form a galvanic circuit, when the gold will be immediately whitened. A solution of nitrate of silver will, under similar circumstances, occasion on the gold a white precipitate, but as no amalgamation takes place, it is readily wiped off, and cannot possibly occasion any fallacy.[[526]]
Certain metals likewise decompose solutions of this salt, by virtue of superior affinity; in those cases where the precipitating metal is capable of forming a direct union with Mercury, we shall find the precipitates to consist of an amalgam of the metal employed; where no such combination takes place, the mercury will be frequently seen standing on the surface as a metallic dew. This is particularly striking where iron or steel has been employed; these metals are also at the same time blackened by it.
Brugnatelli[[527]] has proposed the following method of distinguishing corrosive sublimate from arsenic—Take a quantity of fresh wheat starch, mix with water, and add a sufficient quantity of iodine to give the liquid a blue colour; if corrosive sublimate or arsenic be added to this liquor, the colour is alike destroyed and it becomes reddish, but if the change has been effected by the latter substance, a few drops of sulphuric acid will restore the blue colour, but if by the former it is not recoverable by such means.[[528]]
HYDRARGYRI SUB-MURIAS. L.