This substance is procured by making incisions through the bark of the Norway Spruce fir, and afterwards boiling the flakes so obtained in water, and then straining the resin through coarse cloths under a press; whereas frankincense (Abietis resina) is a spontaneous exudation from it. It is now entirely confined to external use, as a rubefacient spread on leather; it is very adhesive. Emplast: Picis comp. L. Emplast: Picis Burgund. D. Adulterations. A factitious sort, manufactured in England, is often met with; it is to be distinguished by its friability, and its want of viscidity and unctuosity, and by the absence of that peculiar odour which characterises the genuine specimens.

This fluid is formed from the decomposition of the resinous juice of the pine, during the slow and smothered combustion of its branches, and as a summary definition of the substance, that by Pliny cannot be surpassed, “Pix nihil aliud quam combustæ resinæ fluxus.” Lib. 23. c. 1. Chemical Composition. It is found to consist of empyreumatic oil, resin, acetic acid, and some salts. Solubility. Water readily dissolves a portion of Tar, and forms a solution of the colour of Madeira wine, with a sharp empyreumatic taste. Med. Uses. Tar water, under the auspices of Bishop Berkley, was formerly considered a remedy of extraordinary powers;^[600] this opinion however has at length passed away, (see page 27.) and Tar is now particularly indebted for a place in the Materia Medica, to an essay by Sir Alexander Crichton, entitled, “An Account of some Experiments made with the Vapour of boiling Tar,^[601] in the cure of Pulmonary Consumption.” At the request of Sir Alexander, I was induced to make a trial of its effects, and I do not feel any hesitation in stating that the result has led me to believe that it may, in some cases, be attended with benefit. In the application of the remedy several precautions are necessary for its success. The Tar employed should be that used in the cordage of ships; to every pound of which half an ounce of sub-carbonate of potass must be added, in order to neutralize the pyroligneous acid generally found mixed with the tar, the presence of which will necessarily excite coughing; the tar thus prepared is to be placed in a suitable vessel over a lamp, and to be kept slowly boiling in the chamber during the night as well as the day; the vessel however ought to be cleaned and replenished every twenty-four hours, otherwise the residuum may be burnt and decomposed, a circumstance which will occasion increased cough and oppression on the chest. The ancients entertained a high opinion of the efficacy of Tar in pulmonary diseases, when internally administered; supposing it to promote expectoration, relieve dyspnæa, and check spitting of blood; Dioscorides particularly speaks of its utility in such cases; he also recommends it to be applied to ulcers, which he says it fills up and heals, whether they be situated on the surface of the body, or in the ears, throat, and other internal parts. See the chapter on “Inhalations,” page 202. Officinal Prep. Unguent. Picis Liquidæ. L.

Chemical Composition. The composition of this substance has not until lately been well understood, and hence the different appellations bestowed upon it by the different colleges. Solubility. It is insoluble in water, but soluble in pure potass. Uses. It is only employed externally, by sprinkling on excoriated parts; the safety of such a practice however is questionable. Officinal Prep. Unguent. Ceruss. D. Plumbi Acetas L.E.D. (K) Adulterations. Chalk may be detected by assaying its solution in cold acetic acid with oxalate of ammonia; Carbonate of barytes, by adding to a portion of the same solution, sulphate of soda very largely diluted with distilled water; and Sulphate of barytes, or Sulphate of lead, by the insolubility of the white lead in boiling distilled vinegar.

It is a yellow protoxide of lead, which has been melted and left to crystallize by cooling. It is only employed in pharmacy for forming other preparations of lead, and the following officinal plasters, Emplast. Plumbi, L. E.D. Ceratum Saponis. L. It is added to wines to remove their acidity; for the detection of which, evaporate the suspected liquor to a thick fluid, add charcoal, and calcine in a crucible: in the space of an hour metallic points will be obtained, consisting of lead surrounded by a quantity of yellow protoxide.

Qualities. Form, irregular masses resembling lumps of sugar, being an aggregation of acicular four-sided prisms terminated by dihedral summits, which are slightly efflorescent; by careful crystallization, it may be obtained in quadrangular prisms. Taste, sweet and astringent. Chemical Composition. Although it has been termed a Super-acetate, it appears to be a neutral salt, and that its power of reddening valuable blues is attributable to a partial decomposition; for when dissolved in water containing the least portion of carbonic acid, a white carbonate of lead is precipitated, and a corresponding portion of acetic acid is necessarily disengaged. The College have therefore now designated it as an acetate. According to the experiments of Berzelius, this salt, in its anhydrous state, consists of one proportional of acetic acid, and one proportional of oxide of lead; so that the proportion of the metallic base is one-third of that in the sub-acetate. Solubility. It is dissolved in 25 parts of water, hot or cold; it is also soluble in alcohol. When common water is employed the solution is quite turbid, unless a small proportion of acetic acid be previously added. Incompatible Substances. The alkalies, alkaline earths and their carbonates; most of the acids; alum; borax; the sulphates, and muriates; soaps; all sulphurets; ammoniated, and tartarized iron; tartarized antimony; undistilled water. The solution of acetate of ammonia decomposes that of this salt, in consequence of the carbonic acid which is generally diffused through it. It has lately been discovered that Gallic acid and Tannin are capable of combining with lead in solution, and of forming a perfectly insoluble substance, which falls to the bottom of the vessel; hence all vegetable astringents must be considered as incompatible with this medicine. On this account, liquors which have been kept in oak casks,^[603] for a certain time, must be freed from lead. This explains a fact, with respect to the effect of new rum in the West Indies, of some importance. This spirit, when newly distilled, is found to contain traces of lead, derived from the leaden rims of the coppers, and the leaden worm, used for its condensation; but, by being kept about twelve months in oaken casks, it loses its deleterious properties, and no longer exhibits any traces of this metal.^[604] Certain bodies appear likewise to be incompatible with the compounds of lead, not from the chemical changes they induce, but from the contrary effects they produce upon the body; thus mercury appears to invalidate their powers and to counteract their effects, as we may have observed in treating saturnine cholic. I suspect also that antimony operates in the same manner; M. Merat relates the case of an apothecary who was cured of a desperate saturnine cholic, after having taken, in the course of eight days, eighty grains of tartarized antimony. Med. Uses. I feel no hesitation in pronouncing this salt of lead to be one of the most valuable resources of physic; from the results of numerous cases, I state with confidence that it is more efficient in stopping pulmonary and uterine hemorrhage, than any other known remedy—“nil simile, nec secundum,”—and that its application is equally safe and manageable; but it must not be combined with substances capable of decomposing it, nor must it be simultaneously administered with the medicines which are frequently prescribed in conjunction with it, as an Infusion of Roses, Sulphate of Magnesia, &c. Alum has also been in some cases added to it, with the intention of increasing its astringency. It is evident that under such circumstances an insoluble and inert Sulphate of Lead will be produced. The experiments of Orfila confirm the truth of these views, and shew that such substances act as counter-poisons for the salts of lead. According to my experience, those vegetable acids which decompose the acetate of lead, and form insoluble salts with its base, are not medically incompatible, when administered simultaneously with it, although no scientific physician would prescribe such a mixture; this fact is shewn by the circumstance of potations, containing malic and tartaric^[605] acids, not having been found to invalidate the efficacy of this salt. Whether the stomach in the first instance prevents the decomposition, and its necessary results, or allows the operation of the usual affinities, and then subsequently decomposes the insoluble compound which results from them, by the abstraction and digestion of its vegetable constituent, are questions for future inquiry, when the laws of gastric chemistry shall be better understood, and more justly appreciated. I have also seen much benefit accrue from this medicine in protracted diarrhœa, when it has checked the bowels more effectually even than opium. M. Gaspard has communicated to the public, through the medium of Majendie’s Journal de Physiologie, (3 numéro Juillet, 1821,) a paper upon the operation of Acetate of Lead, entitled “Experiences Physiologiques et Medicales sur L’Acetate de Plomb,” in which he asserts that this metallic salt cannot be administered without risk in any dose, unless indeed it be given in vehicles which decompose it, and which, he adds, appears generally to have happened in the prescriptions of those who have given it extensively. He observes, that “it produces a slow and peculiar inflammation of the bowels, as well as of the lungs; and that it, moreover, occasions Cholica Pictonum.” No one, I apprehend, will deny the poisonous quality of acetate of lead, any more than that of arsenic; and yet both may, by proper management, be rendered therapeutical agents of value and safety. Forms of Exhibition. In that of pill, guarded by opium; it will be prudent to recommend an abstinence from all potation, except that of cold water, or draughts, composed of diluted acetic acid, for at least an hour after the ingestion of the pill.^[606] Dose, gr. ½ to gr. j. Form. 57. Officinal Prep. Cerat. Plumb. acetat. L.^[607]

[This plant is found in almost every part of the United States in low and moist situations. It flowers in May and June, and the root is the only part used in medicine. By analysis this is found to contain resin, bitter extractive, fœcula, and a slight proportion of a gummy substance. The root of the May Apple is an excellent active cathartic, operating in a manner very similar to the common Julap. It is given in powder, in doses of about grs. xx. The proper period for collecting the root for medicinal purposes is the autumn, when the leaves of the plant have turned yellow. It should be carefully dried and then pulverized.]

The addition of lime to potass renders it less deliquescent, and more manageable, as an escharotic.

Qualities. Form, a white brittle substance, extremely caustic and deliquescent, and possessing in an eminent degree all the properties denominated alkaline. Solubility. f℥j of water dissolves ʒvij; it is also soluble in alcohol. Chemical Composition. This preparation, independent of its impurities, is the hydrated protoxide of potassium, although in the state in which it is cast into sticks it generally contains a little Peroxide,^[608] and therefore evolves oxygen when dissolved in water. Med. Uses. It is a most powerful caustic (causticum commune acerrimum), and is frequently employed to establish an ulcer; or, instead of incision, to open a tumour. It has the advantage of other caustics, from the circumstance of our being able to neutralize its powers by touching it with vinegar, and thus to arrest its progress in an instant; it is however more liable to produce a large eschar than nitrate of silver, in consequence of the chemical action of the alkali upon the skin. Within the last few years, surgeons have greatly preferred the use of this caustic to that of nitrate of silver, in cases of organic stricture of the urethra, as acting more powerfully, and yet occasioning less irritation than the latter substance; it is also said that the part which it destroys is sooner detached and more easily eliminated. Its disposition, however, to extend its sphere of action has occasioned such a destruction of the membrane as to allow the urine to pass into the cellular substance, by which very serious effects have been produced. For this reason there are cases in which the nitrate of silver is still to be preferred. As an internal remedy it is only employed in solution. See Liquor Potassæ.^[609]

Acetas Kali. D. Kali Acetatum. P.L. 1787.—Sal diureticus. P.L. 1745.—Terra foliata Tartari.—Sal Sennerti.—Magisterium Purgans Tartari.—Sal Essentiale vini. Oleum Tartari Sennerti.—Sal digestivus Sylvii, &c.

Qualities. Form, masses of a foliated, laminar texture, extremely deliquescent; Odour, slight and peculiar; Taste, sharp and pungent. Solubility. f℥j of distilled water at 60° dissolves 404 grains, or 100 parts of it are soluble in 105 parts of water; the solution soon undergoes spontaneous decomposition; it is soluble in four times its weight of alcohol.—Chemical Composition. It consists of one proportional of each of its components, or 48 potass and 50 acetic acid. Incompatible Substances. It is decomposed by tamarinds and most sub-acid fruits; by almost every acid, as well as every variety of neutral salt, whether alkaline, acid, or metallic. Med. Uses. In small doses, diuretic; in larger ones, mildly cathartic. Dose, ℈j to ʒj to produce the former, ʒij to ʒiij to excite the latter of these effects. Forms of Exhibition. On account of its deliquescent property it is not admissible in powders or pills, but should be always exhibited in solution. (Form. 108, 110, 111.) In the former editions of this work, I introduced under the present article, those views regarding the operation of saline bodies upon the kidneys, and their decomposition by the digestive organs, which I considered as capable of throwing some light upon the medicinal operation of these bodies. Having, however, in the present edition of my work devoted a chapter to the consideration of Diuretics, I have necessarily removed all my general observations upon this subject to that part of the work; I therefore entreat the reader to refer to the first part, page 93. Alibert, in speaking of the diuretic virtues of this salt, says that it is so well suited to the sensibility of the Absorbents that its administration is frequently followed by very salutary effects. (Elémens de Thérapeutique, vol. i. p. 327.)

Adulterations. Tartrate of potass is discovered by adding a solution of tartaric acid, which will occasion with it a copious precipitate; the sulphates, by their forming with acetate of lead, or muriate of baryta, precipitates insoluble in acetic or muriatic acid. The brown tinge which it frequently exhibits depends upon the same cause as that which usually imparts colour to the Liquor. Ammon. Acet. This salt is also sometimes contaminated with lead, which arises from its having been prepared by decomposing the acetate of lead by means of carbonate of potass.

Qualities. Form, crystals which are four-sided prisms with dihedral summits, permanent in the air; Taste, slightly alkaline without acrimony. Chemical Composition. It is a bi-carbonate, consisting of two proportionals of carbonic acid and one proportional of potass; and in its crystalline form, it also contains water equal to one proportional. Solubility. It is soluble in 4 parts of cold, and in ⅚ths of its weight of boiling water, in which it is partially decomposed, carbonic acid being emitted during the solution; it is quite insoluble in alcohol. Med. Uses. In cases where an alkali is indicated, this preparation offers an agreeable and efficient remedy; and experience has shewn that its additional proportion of carbonic acid does not in the least invalidate its alkaline agency. In disordered states of the digestive functions, alkalies frequently act with surprising effect; in calculous affections their value has been already noticed (see Liquor Potassæ), and the stomach appears to bear the protracted exhibition of the carbonate of potass or soda, with more temper than it does that of any other alkaline combination; and on account of the increased quantity of carbonic acid which this salt contains, it is preferable for effervescing draughts. (See Acid. Citric. and Form. 123, 168.) Incompatible Substances. Acids and acidulous salts; borax; muriate of ammonia; acetate of ammonia; alum; sulphate of magnesia; lime water; nitrate of silver; ammoniated copper; muriate of iron; sub-muriate and oxy-muriate of mercury; acetate of lead; tartarized antimony; tartarized iron; the sulphates of zinc, copper, iron, &c. Dose, grs. x to ʒss.

Qualities. Form, crystals which are six-sided prisms usually terminated by dihedral summits. Taste, bitter and sharp with a sensation of cold. Chemical Composition. It consists of one proportional of nitric acid, and one proportional of potass. Solubility. It dissolves in seven parts of water at 60°, and in its own weight at 212°. Its solubility is considerably increased by adding muriate of soda to the water; its solution is attended with a great reduction of temperature; it is quite insoluble in alcohol. Incompatible Substances. Alum; sulphate of magnesia; sulphuric acid; the sulphates of zinc, copper, and iron; according to the usual laws of affinity, it should be also decomposed by sulphate of soda; this however only takes place at the temperature of 32°, and then but partially. Med. Uses. Refrigerant, in which case the draught should be swallowed immediately after the solution of the salt is complete, for if it be allowed to stand for some time, its effect with regard to cooling is not nearly so evident (see Form. 138, 144); as a diuretic, its powers are too inconsiderable to be employed, except in combination (Form. 102, 109, 115, 170); a solution of ʒj to f℥vj of rose water forms a good detergent gargle, and a small portion allowed to dissolve slowly in the mouth, will frequently remove an incipient inflammation of the tonsils: for its modus operandi as a diuretic, see Potassæ Acetas. Dose, grs. x to xv, as a diuretic or refrigerant; grs. xxv to xl are aperient, and in large doses it excites vomiting, bloody stools, convulsions, and even death. The best antidotes are opium and aromatics. Impurities. As it occurs from the hand of nature it is far from pure, and even by art it is freed with difficulty from sea salt; the presence and quantity of which in any specimen, may be learnt by adding nitrate of silver to its solution as long as any precipitate is produced.

Before the nature of this salt was well understood, it received various appellations according to the different methods by which it was procured, and it was supposed to possess as many different virtues, as Salt of Wormwood, Salt of Tartar, Salt of Bean Stalks, &c.

Qualities. Form, coarse white grains, so deliquescent, that by exposure to air they form a dense solution, (Oleum Tartari per deliquium, P.L. 1720.) Taste, alkaline and urinous.^[610] Chemical Composition. This salt, although far from being pure, is sufficiently so for every pharmaceutical purpose. It consists of one proportional of acid and one proportional of potass, with variable quantities of sulphate of potass, muriate of potass, siliceous earth, alumina, together with the oxides of iron, and manganese. Solubility. It is dissolved by twice its weight of water; the residue, if any, may be considered as impurity; it is insoluble in alcohol; with oils it combines, and forms soaps. Incompatible Substances. They are enumerated under Potassæ Carbonas. Med. Uses. Antacid, and diuretic, (Form. 101, 107, 129), but it is far less pleasant than the carbonate; it is principally used for making saline draughts, see Acid. Citric. and Form. 107. Dose, grs. x to ʒss. Officinal Prep. Potassæ Acetas, L.E.D. (I) Liquor Potassæ L.E.D. (K) Potassæ Sulphuretum (I) L.E.D. Potassæ Tart. L.E.D. (I) Liquor Arsenicalis (I.L.) Adulterations. Its degree of purity may be estimated by the quantity of nitric acid, of a given density, requisite for the saturation of a given weight. The purest sub-carbonate is that obtained by incinerating cream of tartar, since most of the impurities are decomposed by the heat during the process, (Sub-carbonas Potassæ Purissimus. E.); it however generally contains lime.

Qualities. Form, crystals which are right rectangular (but not square) prisms, modified on the edges and angles; or double six-sided pyramids with short intervening prisms, which are macles, or hemitrope crystals; they are slightly efflorescent, and when heated they decrepitate. Solubility. f℥j of water dissolves only grs. 24: the salt is insoluble in alcohol. Incompatible Substances. It is partially decomposed by the nitric and muriatic acids, in which case, a portion of the base being saturated, a corresponding portion of bi-sulphate results; this fact illustrates a chemical law of some importance, viz. that a substance less weakly attracted by another than a third, will sometimes precipitate this third from its combination with the second, in cases wherein a super, or sub-salt is readily formed.^[611] The history of tartrate of potass will furnish farther illustrations. See page 183. Sulphate of potass, when in solution, is entirely decomposed by lime and its compounds; by oxy-muriate of mercury; nitrate of silver; and by acetate and sub-acetate of lead. Med. Uses. On account of its insolubility, it does not possess much activity as a purgative, but is said to be powerfully deobstruent; it should be exhibited in the form of powder, and in conjunction with rhubarb, or some other purgative medicine. Dose, grs. x to ℥ss. Form. 94. From its hardness and insolubility, it is a most eligible substance for triturating and dividing powders. Officinal Prep. Pulv. Ipecac. co. L.E.D. (M) Under the name Sulphas Potassæ cum Sulphure, the Edinburgh college retains the preparation formerly known by the name Sal Polycrest (Salt of many virtues); and as it is produced by deflagrating nitre with sulphur, the product, besides sulphate of potass, contains bi-sulphate and sulphuret of potass. It possesses no superiority over the common sulphate.

Qualities. Crystals, long hexangular prisms; Taste, sour and slightly bitter. Chemical Composition. It is a bi-sulphate, consisting of two proportionals of acid, and one proportional of base. Solubility. It is soluble in twice its weight of water, as well as in alcohol. Med. Uses. It affords a convenient mode of exhibiting sulphuric acid combined with a saline purgative, in a solid form; as it is more soluble, so is it more active than the sulphate. Dose, grs. x to ʒij. It forms a grateful adjunct to rhubarb. See Form. 85.

Qualities. Form, a hard brittle mass; Colour, liver brown, hence the old name of hepar; Taste, acrid and bitter; Odour, none when dry, but if moistened, it yields the stench of sulphuretted hydrogen. Chemical Composition. I consider this substance as a mixture of Sulphate of Potass, with variable quantities of Sulphuret and Bi-Sulphuret of Potassium.^[612] Incompatible Substances. It is instantly decomposed by water, the oxygen of which forms Potass with the Potassium; while its hydrogen, combining with the sulphur, produces Sulphuretted hydrogen, part of which escapes, and another part forms, with the excess of Sulphur, Bi-Sulphuretted hydrogen; this latter body uniting with the base, produces what has been termed an Hydroguretted Sulphuret, but which might be more properly called an Hydro-bi-Sulphuret; upon adding an acid to the solution, a quantity of Sulphur is thrown down, Sulphuretted hydrogen is evolved, and a salt of Potass remains in solution. Metallic salts also decompose it, the metal falling down as a Sulphuret, or Hydro-sulphuret. Medicinal Uses. It presents us with a form in which sulphur is soluble in water; it is diaphoretic, and has been found advantageous in cutaneous affections, (Form. 118,) and in arthritic and rheumatic complaints; while, from its known chemical action on metallic salts, it has been proposed as an antidote to such poisons. Its solution has been lately recommended as a lotion for the itch of infants, and in some cases it has been known to succeed after the sulphur ointment had failed.^[613]

Qualities. Form, small irregular brittle crystals, which when reduced to powder are termed cream of tartar. Taste, harsh and acid. Chemical Composition. It is a bi-tartrate, consisting of two proportionals of acid and one proportional of potass. Solubility. It requires 120 parts of water at 60°, and 30 parts at 212°, for its solution; it is slightly soluble in alcohol. The watery solution of this salt was first observed by Berthollet to undergo a spontaneous decomposition by keeping, during which a mucous matter is deposited, and there remains a solution of carbonate of potass coloured with a little oil. It has long been regarded a pharmaceutical desideratum to increase the solubility of cream of tartar; Vogel discovered that it might be accomplished by combining it with boracic acid, and accordingly a formula has been introduced into the Codex Medicamentarius of Paris, for preparing a “Tartras Acidulus Potassæ Solubilis, admixto Acido Boracico.” The following is the process. Let thirty parts of boracic acid, and twenty parts of distilled water be heated together in a silver dish; as soon as this has been effected, add, in divided portions, 120 parts of super-tartrate of potass, taking care to shake the mixture continually; the whole will soon liquefy, (“mire liquescent,”) and by continuing the heat, a pulverulent mass will result. As it is extremely deliquescent it must be carefully preserved from the contact of the air; it dissolves in its own weight of water at 55°, and in half its weight at 212°. It is probable that the result is a new salt, in which the boracic and tartaric acids exist in combination,^[614] but grant even that the chemical identity of the super-tartrate is preserved inviolate in the compound, I would ask what medical advantage can possibly attend the discovery? The peculiar value of cream of tartar depends doubtless upon its comparative insolubility, as I have already stated at page 173; modify this, and you will instantly change the medicinal effects of the salt; for like the neutral tartrate it will act upon the bowels, and therefore cease to undergo those changes in transitu which are essential to its characteristic operation. Alum also has been observed by Berthollet to have in some measure the same effect in increasing the solubility of cream of tartar. Incompatible Substances. Alkalies and alkaline earths; the mineral acids, &c. Med. Uses. In doses of ʒiv to ʒvj, it acts as a hydragogue cathartic, producing a considerable discharge of serous fluid into the intestines; when however it is often repeated, it is liable to occasion debility of the digestive organs, and consequent emaciation: in smaller doses it acts as a diuretic. (Form. 112.) ʒj in oj of boiling water, flavoured with lemon peel and sugar, forms when cool an agreeable beverage well known by the name of Imperial. A Cream of Tartar Whey may be made, by adding to a pint of milk (when it begins to boil) ʒij of Cream of Tartar; the pan must then be removed from the fire, the whole suffered to cool, and the whey separated from the curd by straining; this whey, diluted with warm water, furnishes an excellent drink in Dropsy. As it decomposes the carbonate of potass, the union of these salts will afford a very pleasant purgative draught. (Form. 82.) Officinal Preparations. Pulv. Jalap. comp. E. (BM) Pulv. Scammon. E. Pulv. Sennæ comp. L. Ferrum Tartarizatum, L. (I) Antimonium Tartarizatum L.E. D. (I) Soda Tartarizata, L.E.D. (I) Adulterations. Super-sulphate of potass (Sal Enixum,) is the substance with which tartar is usually adulterated; it may be detected by its superior solubility, and by the solution affording with muriate of baryta a precipitate insoluble in muriatic acid.^[615]

Qualities. Form; this salt, although ordered to be crystallized, is generally kept in its granular form. Taste, bitter and cool. Chemical Composition. It consists of one proportional of acid, and one proportional of base. Solubility. When in its crystalline form it is soluble in its own weight of water, but in its ordinary granular form, 4 parts are required for its solution; hence, compared with the insoluble super-tartrate, it has justly acquired the name of soluble tartar; when long kept in solution, its acid is decomposed, and its alkali remains in a state of a sub-carbonate. It is also readily soluble in alcohol. Incompatible Substances. Magnesia, baryta, and lime; acetate and sub-acetate of lead, and nitrate of silver decompose it. All acids, even the carbonic,^[616] and acidulous salts, tamarinds, and other sub-acid vegetables, by neutralizing a proportion of the base, convert it into the state of super-tartrate; this fact offers another illustration of the chemical law of affinity, explained under the head of sulphate of potass. The practitioner should bear this in his recollection, for I have frequently seen a dose of soluble tartar directed in the acidulated infusion of roses; the result was of course very different from that which the author of the prescription intended to produce. Med. Uses. It is a mild and efficient purgative, and forms a very valuable adjunct to resinous purgatives or to senna, the griping properties of which it corrects by accelerating their operation. Form. 70. Dose, ʒj to ℥j, in solution.

For the administration and advantages of this form of preparation, see page 190. The following Officinal Formulæ offer some valuable combinations.

Pulvis Aloes compositus. L. Pulvis Aloes cum Guaiaco. D. It consists of aloes three parts, guaiacum two (G), and compound powder of cinnamon one part (O). It combines sudorific and purgative effects. Dose, grs. x to ℈j. See Form. 80.

Pulvis Aloes cum Canella. D. and P.L. 1807. Aloes four parts, white canella (E) one part. It is known in the shops by the name of Hiera Picra. The compound is more adapted for the form of pills than that of powder. It is very generally used by the lower classes, infused in gin. Dose, grs. x to ℈j.

Pulvis Antimonialis. L.D. Oxidum Antimonii cum phosphate Calcis. E. This preparation was introduced into the Pharmacopœia, as the succedaneum of the celebrated fever powder of Dr. James, the composition of which was ascertained by Dr. George Pearson. (Phil. Trans. lxxxi. 317.) It consists of 43 parts of the phosphate of lime, mixed, or perhaps chemically combined, with 57 parts of oxide of antimony, of which a portion is vitrified; and it is probable, that the difference of the two remedies depends principally upon the quantity of oxide which is vitrified: the specification of the original medicine is worded with all the ambiguity of an ancient oracle, and cannot be prepared by the process as it is described.^[617] Experience has established the fact, that James’s Powder is less active than its imitation; it affects the bowels and stomach very slightly, and passes off more readily by perspiration; in general however the difference is so inconsiderable, that we need not regret the want of the original receipt.^[618] As it is quite insoluble in water, it should be given in powder, or made into pills. It is diaphoretic, alterative, emetic, or purgative, according to the extent of the dose and the state of the patient; in combination it offers several valuable resources to the intelligent practitioner. (See Form. 119, 121, 125, 129, 134.) But it may be fairly questioned whether this remedy has not been far too highly appreciated. Dr. James was certainly very successful in its use, but it must not be forgotten that he usually combined it with some mercurial, and always followed it up with large doses of bark.

Pulvis Cinnamomi Compositus. L. Cinnamon bark four, cardamom seeds (B) three, ginger root (B) two, long pepper (B) one part. It is principally used to give warmth to other preparations, e. g. Pulv. Aloes. comp. L.D.

Pulvis Contrayervæ Compositus. L. Contrayerva, five, prepared shells, eighteen parts (M). Dose, grs. x. to xl. It is said to be stimulant and diaphoretic.

Pulvis Cornu Usti cum Opio. L. Opium one part, burnt hartshorn eight, powdered cochineal one part. Ten grains contain one of opium.

Pulvis Cretæ Compositus. Prepared chalk twelve parts, tormentil root (G), acacia gum (M), of each six, cinnamon bark eight (E), long pepper (E) one part. It is antacid, astringent, and carminative. Dose, grs. v to ℈j.

Pulvis Cretæ Compositus cum Opio. L. Compound powder of chalk thirty-nine parts, opium one part. Form. 151.

Pulvis Ipecacuanhæ Compositus. L.E.D. Ipecacuan one part, opium (H) one part, sulphate of potass (M) eight parts. This combination has been long established in practice, as a valuable sudorific, under the name of Dover’s Powder. It affords one of the best examples of the power which one medicine possesses of so changing the action of another, as to produce a remedy of new properties; in this combination the opium is so modified, that it may be given with perfect safety and advantage in inflammatory affections accompanied with increased vascular action: it would seem that whilst the opium increases the force of the circulation, the ipecacuan relaxes the exhalant vessels, and causes a copious diaphoresis: the sulphate of potass is also an important ingredient, for experience has fully proved that ipecacuan and opium, in the same proportions, have not so powerful an effect without it; its action must be purely mechanical, dividing and mixing the active particles more intimately, and it appears that the success of the remedy depends very much upon its being finely powdered. Dose, grs. v. to ℈j, diffused in gruel, or in the form of a bolus. (See Form. 120, 121, 122.) The saline constituent in the original Dover’s Powder, was the result of the deflagration of nitre, and was therefore deliquescent; its dose was as much as from 40 to 70 grains. In the Codex of Paris, this compound is directed to be prepared by melting together four parts of sulphate of potass, with an equal proportion of nitrate of potass; to which when nearly cold is to be added, and well mixed by triture, one part of pulverized extract of opium; the powders of ipecacuan and liquorice root, of each one part, are to be added last. It is evident that the proportions of opium and ipecacuan in this combination, are less than those in ours, and yet it is said to be more powerfully diaphoretic on account of the nitre. An arrangement, which is indebted for its medicinal virtue to a similar mode of operation, is presented in Form. 130.

Pulvis Scammoniæ Compositus. L. Scammony and hard extract of jalap, of each four parts, ginger root (E) one part. The Edinburgh preparation of the same name differs very materially in composition, its ingredients being scammony and cream of tartar in equal parts.

Pulvis Tragacanthæ Compositus. L. Powdered Tragacanth, acacia gum, and starch, of each one part; refined sugar, two parts. From what has been already stated under the head of mucilage of tragacanth, it appears to be a superfluous, if not an injudicious demulcent; and since starch is insoluble in cold water, the object for introducing it is not very obvious. Form. 120.

Powders should be preserved in opaque green bottles, as they are materially affected by the action of light and air. Many of the compound ones should be considered as extemporaneous, and ought to be prepared only when they are required. The practitioner is also cautioned against purchasing any medicine in its powdered form, for so universal is the system of adulteration, that regular formulæ are observed in the wholesale houses for sophisticating powders, and Mr. Gray, in his “Supplement to the Pharmacopœias,” has given several specimens, under the title of “Pulveres Reducti.”