Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 54

8. (PRECIPITATED CALOMEL; CALOMELAS PRaeCIPITATUM, L.) Digest pure quicksilver, 9 parts, in nitric acid (sp. gr. 102 to 125), 8 parts, until no more metal will dissolve, applying heat as the effervescence ceases; then mix the hot liquid quickly with a boiling solution of sodium chloride, 8 parts, dissolved in water (slightly acidulated with hydrochloric acid), 64 parts; lastly, well wash the precipitate in boiling distilled water, and dry it. The product, when the process is skilfully managed, is perfectly white and pure.

_Prop._ A heavy, white, tasteless powder; insoluble in water, alcohol, and cold dilute nitric acid; volatilises at a temperature below redness, and yields a white or yellowish-white sublimate; hot nitric acid oxidises and dissolves it; alkalies, the alkaline carbonates, and lime water, decompose it, with the production of the black oxide; ammonia converts it into a dark slate-grey coloured powder (BLACK PRECIPITATE--Kane). Sp. gr. 714 (Boullay; 7156--Pelouze and Fremy; 7176--Ure).

_Pur._ Calomel is frequently contaminated with small quant.i.ties of corrosive sublimate, which may be detected by digesting a little in alcohol, decanting the clear portion, and testing it with a drop or two of pota.s.sium hydrate, when a reddish precipitate will be formed if any mercuric chloride be present. It is pulverulent, whitish, and sublimes entirely by heat. It becomes black on the addition of pota.s.sium hydrate, then, heat being applied, it runs into globules of mercury. Neither silver nitrate, lime water, nor sulphuretted hydrogen, being added to the water in which it has been washed, or boiled throws down anything.

_Uses._ Calomel is one of the milder mercurials, and in this respect takes its position immediately after blue pill, mercury with chalk, and the grey oxide; but it probably ranks before all the other salts of mercury.

Universal experience appears to show it to be a most valuable alterative when judiciously administered. With this intention it is given in doses of 1/4 to 1 gr., generally combined with antimonials, as in Plummer's pill, and repeated every night, or every other night, for some time, followed by a mild saline aperient in the morning. As a purgative, 2 to 5 gr., either combined with or followed by other purgatives, as jalap, rhubarb, senna, colocynth, Epsom salts, &c. As a vermifuge, 2 to 5 gr., over-night, followed by a sufficient dose of castor oil next morning. Combined with opium it is frequently used in various complaints to produce salivation, or bring the system under the influence of mercury. It is also employed as a sedative and errhine, and in a vast number of other indications. It is, indeed, more frequently used, and in a greater variety of complaints, than probably any other medicine.

_Obs._ Of the two methods of preparing calomel, that by precipitation is not only the best, but the most economical. That by sublimation is, however, the one generally adopted in England. Mr Brande states that "a small portion of sodium chloride is apt to remain combined with it, which might affect its medical uses." Such a contamination is not found in carefully prepared precipitated calomel, although we doubt whether the quant.i.ty of it which exists in any of the samples we have met with (being merely a trace) would at all interfere with its therapeutical action; more especially when it is recollected that alkaline chlorides are present in, not merely the primae viae, but also in every part of the animal body. The late Mr Fownes, a chemist who was unsurpa.s.sed in the accuracy of his researches, and the caution and delicacy with which he expressed his opinions, once a.s.sured us that calomel was more easily and cheaply prepared of the best quality by precipitation than by sublimation, and that if, from careless manipulation, it occasionally contained a minute quant.i.ty of common salt, this was of much less importance than the contamination of corrosive sublimate, which was frequently present in samples of sublimed calomel.

To produce a superior article of calomel in the dry way is a somewhat difficult task, and the process frequently fails in the hands of inexperienced operators. The solution of the mercury is best made in an iron vessel, and the sublimation should be conducted (preferably) in an earthenware retort with a short but very wide neck, and fitted in a s.p.a.cious receiver, having a large flat bottom, also of earthenware, and containing a little cold water. On the small scale the heat may be applied by means of a sand bath. The form above given for calomel, by precipitation, produces a large product, perfectly free from corrosive sublimate and mercurous nitrate, and is consequently free from the objections frequently raised against that mode of preparing it.

"The form in which calomel sublimes depends much upon the dimensions and temperature of the subliming vessels. In small vessels it generally condenses in a crystalline cake, the interior surface of which is often covered with beautiful quadrangular prismatic crystals, transparent, and of a texture somewhat elastic or h.o.r.n.y. In this state it acquires, by the necessary rubbing into powder, a decided yellow or buff colour, more or less deep, according to the degree of trituration it has undergone. If, on the contrary, the calomel be sublimed into a very capacious and cold receiver, it falls in an impalpable and perfectly white powder, which requires only one elutriation to fit it for use; it then remains perfectly colourless." (Brande.)

The long-continued action of steam on calomel in a state of minute division is attended by the formation of a small quant.i.ty of corrosive sublimate. (Righini.) Boiling water, hot air, and light, also produce a like effect.

=Mercurous Iodide.= HgI. _Syn._ SUBIODIDE OF MERCURY, GREEN IODIDE OF MERCURY, MERCUROUS IODIDE; HYDRARGYRI IODIDUM VIRIDE (B. P.), HYDRARGYRI SUBIODUM, H. IODIDUM (Ph. L.), H. I. VIRIDE (Ph. D.), L. _Prep._ 1. (B.

P.) Mercury, 1 oz.; iodine, 278 gr.; rectified spirit, a sufficiency. Rub the iodine and mercury in a porcelain mortar, moistening occasionally with a few drops of spirit, and continue the trituration until the ma.s.s a.s.sumes a uniform green colour, and no metallic globules are visible.

2. Precipitate a solution of mercurous nitrate by another of mercurous pota.s.sium iodide; wash the precipitate, first in a solution of sodium chloride, and then in pure water; lastly, dry it in the shade.

3. (Ph. L.) Mercury, 1 oz.; iodine, 5 dr.; triturate together, gradually adding of rectified spirit, q. s. (about 1 to 2 fl. dr.), until globules are no longer seen; dry the powder, by a gentle heat, in the shade, as quickly as possible, and preserve it in a well-stoppered black gla.s.s vessel. The formula of the Ph. D. is similar.

_Prop., &c._ A heavy, greenish-yellow powder; insoluble in water, alcohol, and a solution of common salt; soluble in ether, and slightly so in an aqueous solution of iodide of pota.s.sium. "Freshly prepared, it is yellowish. Heat being cautiously applied, it sublimes in red crystals, which quickly turn yellow, and, on access of light, blacken. It is insoluble in a solution of chloride of sodium." The process of the Ph. L.

and F. P. does not answer when larger quant.i.ties than 4 or 5 oz. are prepared at once, owing to the great heat generated by the reaction of the ingredients, and the consequent volatilisation of a portion of the iodine, by which the colour of the product suffers.--_Dose_, 1/8 to 1 gr., made into pills; "in syphilis and scrofula, especially where they occur in the same individual." It is also used externally, in the form of ointment. It is very poisonous.

=Mercurous Nitrate.= HgNO_{3}. _Syn._ SUBNITRATE OF MERCURY; HYDRARGYRI SUBNITRAS, H. NITRAS, H. PROTONITRAS, L. _Prep._ 1. (Neutral.) By digesting mercury in excess of cold dilute nitric acid, observing to remove the short prismatic crystals within a short time after they are formed; these, when drained, and redissolved in water slightly acidulated with nitric acid, furnish crystals of pure neutral mercurous nitrate by cautious evaporation.

2. (Basic.) Deposited after some time, when excess of mercury has been employed as above. A fine crystallised salt.

_Prop., &c._ Both the above are decomposed by water, but the former may be dissolved in a very small quant.i.ty without decomposition. When the neutral salt is triturated with an excess of sodium chloride, and water subsequently added, the whole of the mercury is thrown down as calomel, and the filtered supernatant liquid does not contain corrosive sublimate.

If this salt is detected, the salt examined contained mercuric nitrate, and if any basic mercurous nitrate was present, the newly formed calomel has a grey or black colour, due to presence of oxide.--_Dose._ Of the neutral salts, 1/16 to 1/8 gr. It is seldom used internally. A solution is sometimes employed as a mild caustic to ulcers; and, more dilute, as a lotion in lepra, porrigo, psoriasis, etc.; or made into an ointment, in the same diseases.

=Mercurous Oxide.= Hg_{2}O. _Syn._ SUBOXIDE OF MERCURY, GREY O. OF M., BLACK O. OF M., MERCUROUS O., DIOXIDE OF M., PROTOXIDE OF M.; HYDRARGYRI SUBOXYDUM, H. OXYDUM, H. O. CINEREUM, H. O. NIGRUM, L. _Prep._ 1. (Ph. L.

1836.) Calomel, 1 oz.; lime water, 1 gall.; mix, agitate well together, decant the clear liquid after subsidence, and well wash the sediment with distilled water; lastly, drain and dry it, wrapped in bibulous paper, in the air.

2. (Ph. D. 1826.) Sublimed calomel, 1 part; solution of pota.s.sium hydrate (warm), 4 parts; triturate together, &c., as last.

3. Briskly triturate calomel in a mortar with pure pota.s.sium hydrate, in excess; wash it with water, and dry it in the shade.

_Prop., &c._ A very dark grey or black powder, suffering decomposition by exposure to light and air, becoming olive coloured, from a portion being resolved into metallic mercury and binoxide. Digested for a short time in dilute hydrochloric acid, it remains undissolved, and the filtered liquid is not affected by pota.s.sium hydrate, or by ammonium oxalate. It is totally soluble in acetic acid, and entirely dissipated by heat. As a medicine pure mercurous oxide is one of the mildest of the mercurials, and is used both internally and externally; but chiefly as a fumigant, or made into an ointment.--_Dose_, 1/2 gr. to 3 gr. twice a day.

=Mercurous Phosphate=, _Syn._ HYDRARGYRI PHOSPHAS, L. _Prep._ Add a solution of mercurous nitrate (slightly acidulated with nitric acid) to a solution of sodium phosphate, and wash and dry the precipitate which forms. In its physical characters it closely resembles calomel, than which it is said to be more appropriate in certain cases, especially in secondary syphilis. Alkalies turn it black.--_Dose_, 1/4 to 1 gr., made into a pill with sugar and aromatics.

=Mercurous Sulphate.= Hg_{2}SO_{4}. _Syn._ SUBSULPHATE OF MERCURY, SULPHATE OF THE SUBOXIDE OF M., PROTOSULPHATE OF M.; HYDRARGYRI SUBSULPHAS, L. _Prep._ By adding sulphuric acid to a solution of mercurous nitrate. The salt falls as a white crystalline powder.

=Mercurous Sulphide.= Hg_{2}S. _Syn._ SUBSULPHATE OF MERCURY; HYDRARGYRI SUBSULPHURETUM c.u.m SULPHURE, H. S. NIGRUM, L. _Prep._ 1. (Pure.) This falls as a black precipitate when a solution of mercurous nitrate is treated with sulphuretted hydrogen or ammonium sulphide.

2. (Impure; ETHIOPS MINERAL; HYDRARGYRI SULPHURETUM c.u.m SULPHURE, H. S.

NIGRUM--Ph. L. 1824 & Ph. D. 1826); (aeTHIOPS MINERALIS--Ph. L. 1836 & Ph.

D. 1826.) (Quicksilver and sulphur, equal parts, triturated together in a stoneware mortar--Ph. D.) until globules are no longer visible.

_Prop., &c._ The last preparation of mercurous sulphide is alone employed medicinally. It is a heavy, insoluble, black powder. It is frequently met with imperfectly prepared, and sometimes adulterated. It is said to be a mixture of mercurous sulphide and sulphur, in variable proportions depending on the length of the trituration. On the large scale it is generally made by melting the ingredients together, and afterwards reducing the ma.s.s to a fine powder in a mill or mortar. It is said to be vermifuge and alterative, and has been used in some cutaneous and glandular diseases, but appears to be nearly inert.--_Dose_, 5 to 30 gr.

=Mercurous Tartrate.= (P. Cod.) _Syn._ PROTO-TARTRATE OF MERCURY, HYDRARGYRI TARTRAS. Made by adding a solution of proto-nitrate of mercury in water, slightly acidulated with nitric acid, to a solution of tartrate of potash as long as a precipitate forms. Wash it with distilled water, dry it in the shade, and keep it in bottles covered with black paper.--_Dose_, 1 to 2 gr.

=MERCURY, Other Preparations of.=

=Mercury, Hahnemann's.= _Syn._ HAHNEMANN'S SOLUBLE MERCURY, H.'S BLACK OXIDE OF M., BLACK PRECIPITATE OF M.; HYDRARGYRI PRaeCIPITATUM NIGRUM, MERCURIUS SOLUBILIS HAHNEMANNI, L.--_a._ By dropping weak ammonia into a solution of mercurous nitrate as long as the precipitate formed is of a black colour; the powder is washed, dried in the shade without artificial heat, and then preserved from the light and air.

(Ph. Bor. 1847.) Solution of mercurous nitrate (recent; sp. gr. 11), 9-1/4 oz.; distilled water, 2 lbs.; mix, filter, and add to the solution of ammonia (sp. gr. 960), 1/2 oz., diluted with water, 4 fl. oz.; collect the powder immediately on a filter, wash it with water, 3 fl. oz., and dry it, &c., as before. A very black powder.--_Dose_, 1/4 to 1 gr.

=Mercury, Precipitates of.= 1. BLACK PRECIPITATE, Hahnemann's soluble mercury (basic mercurous and ammonium nitrate). 2. GREEN P. (MERCURIUS PRaeCIPITATUS VIRIDIS, LACERTA VIRIDIS), from equal parts of mercury and copper, separately dissolved in nitric acid, the solutions mixed, evaporated to dryness, and then calcined until red fumes cease to arise.

Caustic. 3. RED P., mercuric oxide. 4. WHITE P., ammonio-chloride of mercury.

=Mercury, Ward's.= _Syn._ AMMONIO-NITRATE OF MERCURY; HYDRARGYRI AMMONIae NITRAS, L. To nitric acid, 4 parts, contained in a s.p.a.cious bolt-head or matra.s.s, add, gradually, ammonium sesquicarbonate, 2 parts; afterwards add of mercury, 1 part, and digest in a gentle heat, until the solution is complete.

=Mercury with Chalk.= _Syn._ HYDRARGYRUM c.u.m CRETa. GREY POWDER (B. P.) _Prep._ Rub 1 oz. (by weight) of mercury, and prepared chalk, 2 oz., in a porcelain mortar, until metallic globules cease to be visible to the naked eye and the mixture acquires a uniform grey colour.--_Dose._ From 3 to 8 gr.

A little water is said to aid in the extinction of the mercury. Mr Bottle suggests a slight departure from the Grey _modus operandi_ followed by the British Pharmacopia in the above preparation. He proposes to subst.i.tute for the tedious process of trituration in a porcelain mortar the agitation of the mercury with the chalk in a wide-mouthed gla.s.s bottle; by which means the metal may be minutely subdivided, at a considerably less expenditure of time and labour.

=Mercury with Magnesia.= (Ph. D.) _Syn._ HYDRARGYRUM c.u.m MAGNESIa. Pure mercury, 1 oz., carbonate of magnesia, 2 oz. Rub together in a porcelain mortar until the globules cease to be visible and the mixture acquires a uniform, grey colour.--_Dose_, 3 to 8 grains.

=Mercury, Yellow Oxide of.= (Ph. B.) _Syn._ HYDRARGYRI OXYDUM FLAVUM.

_Prep._ Perchloride of mercury, 4 oz.; solution of soda (Ph. B.), 2 pints; distilled water, q. s. Dissolve the perchloride in 4 pints of distilled water, adding the solution by the application of heat, and add this to the solution of soda. Stir them together, allow the yellow precipitate to subside, remove the supernatant liquor by decantation, thoroughly wash the precipitated oxide on a calico filter with distilled water, and finally dry it by the heat of a water bath.

=MES'LIN.= A mixture of various kinds of grain. (Brande.)

=METAGAL'LIC ACID.= Obtained by heating dry gallic acid, by a quick fire, to about 480 Fahr., or until it froths, melts, and becomes black and solid, then dissolving the residuum in an alkali, filtering, and precipitating by an acid. An insoluble, black powder.

=ME'TAL.= _Syn._ METALLUM, L. See METALS.

=METAL'LICA.= [L.] Preparations of the metals. One of the divisions of the Ph. L.

=METAL'LIC TREES.= See VEGETATION (Metallic).

=METAL'LO-CHROMES.= A name given by n.o.bili to extremely thin films of peroxide of lead deposited by electrolytic action upon plates or polished steel, so as to produce an iridescent play of colours. The effect is often very beautiful.

=MET'ALLOIDS.= A name sometimes applied to the NON-METALLIC ELEMENTS.

=METAL'LURGY.= "The art of extracting metals from their ores, and adapting them to various processes of manufacture." (Percy.)

"Notwithstanding the striking a.n.a.logy which exists between common chemical and metallurgic operations, since both are employed to isolate certain bodies from each other, there are essential differences which should be carefully noted. In the first place, the quant.i.ty of materials being always very great in metallurgy, requires corresponding adaptations of apparatus, and often produces peculiar phenomena; in the second place, the agents to be employed for treating great ma.s.ses must be selected with a view to economy, as well as chemical action. In a.n.a.lytical chemistry, the main object being exactness of result and purity of product, little attention is bestowed upon the value of the reagents, on account of the small quant.i.ty required for any particular process. But in smelting metals upon the large scale, profit being the sole object, cheap materials and easy operations are alone admissible."[35]

[Footnote 35: 'Ure's Dict. of Arts, Manufactures, and Mines,' 4th edit.]

The limits of this work do not permit of more than a general reference to the leading operations of metallurgy under this head. These are--digging, picking or sorting, stamping or crushing, and washing, included under the general term, 'dressing ore,'--roasting or calcination, which is either performed with the fuel in contact with the ore, or in reverberatory furnaces; and the liquation or reduction to the reguline form. The application of these processes is noticed under the leading metals. Those who desire to study the subject minutely are referred to the treatises of Dr Percy, Robert Hunt, Karsten, and Le Play.