a spatula, becomes brown at the edge, then suddenly fulminates, and is all dissipated in white fumes. This is a very delicate test; for Dr. Christison informs us that, from a quarter of a grain of oxalic acid dissolved in 4000 parts of water, he and Dr. Coindet procured enough of the oxalate of silver to show its fulmination twice. (Edinburgh Medical Journal, vol. xix. p. 198.) ALKALIES AND SALTS.

here

Under the word ALKALI, and in the article CHEMISTRY, will be found definitions of alkalies and statements of those recent discoveries, more especially of Sir H. Davy, which have thrown new light on their composition. We may repeat that the general properties of these bodies are those of combining with acids forming neutral salts in which the qualities of both the components are lost, of changing the blue colors of vegetables to green, and of combining with oil into a soapy matter which thus occasions, to a certain extent, the union of oil and water. Alkalies

also have an acrid urinous taste; are exceedingly

caustic, so much so as to corrode or dissolve

animal matter; they have a great affinity for water, which, in some cases, they abstract so rapidly and readily even from the atmosphere, that it is necessary to keep them in well-stopped glass bottles, and they are susceptible of fusion or volatilisation by strong heat.

Of the alkalies, the potassa, soda, and ammonia, only are used in pharmacy in an uncombined state.

The London College, adopting the alphabetical order of arrangement, first speak of the preparations of ammonia, then of potassa, and lastly

of soda.

PREPARATIONS OF AMMONIA. Ammonia subcarbonas. London, (formerly called a ammonia præparata, and sal cornu cervi.)— Subcarbonate of ammonia.

Take of muriate of ammonia a pound, prepared chalk dried, one pound and a half. Let them be powdered separately, then mix them and sublime with a gradually increased heat

until the retort become red hot.

Subcarbonas ammonia. Edinburgh. Subcarbonate of ammonia.

Take of muriate of ammonia one part, the softer carbonate of lime, dried, two parts. Let them be separately pulverised, then mixed, and sublimed from a retort into a receiver kept cold. In this formation a double decomposition takes place. The muriatic acid of the muriate of ammonia is attracted by the lime, and the carbonic acid by the ammonia. The subcarbonate of ammonia which is formed sublimes, while the muriate of lime remains in the retort. Qualities.-The salt is commonly seen in a

white, hard, semi-transparent mass. It is solu

ble in water, but when warm water is used it is in some measure decomposed. It is not soluble in alcohol. It is decomposed by the acids and alkalies as well as by their subcarbonates. Magnesia also partially decomposes it. The supertartrate of potassa, sulphate of magnesia, the metallic salts, and some of the earths, also decompose this salt. Its specific gravity is 0.966.

Medical properties.-Subcarbonate of ammo

nia is one of the most useful stimulants whi the pharmacopoeias afford. It may be admin tered in several cases, where, in consequence the inflammatory diathesis which prevails, a ↑ excitants would be inadmissible; as in so instances of erysipelatous inflammation, fer debility, and also in childrens' complaints, pr of its virtues being dependent upon its pow of neutralising acidity in the first passages. atonic gout it is an excellent remedy, as it is some forms of dyspepsia and hysteria. part,' says Dr. Thomson, of pulverised suber of belladonna spread on leather in the form: bonate of ammonia, and three parts of e plaster, is an excellent application for allayus tion from six grains to fifteen. rheumatic pains. Dose for internal adminis It may be co

veniently rubbed down with a scruple of

matic confection.

Liquor ammonia. London.-Solution of

monia.

lime newly burnt six ounces, water four p Take of muriate of ammonia eight ounes Pour one pint of the water upon the lime; tis

cover the vessel and set it aside for an hou Dissolve the muriate of ammonia in the s

mainder of the water previously heated; add it the former mixture, and again cover the vesse after the liquor has become cold strain it

distil twelve fluid ounces of solution of am nia into a receiver whose temperature does exceed 50°. The specific gravity of this soluti is 0.960.

Aqua ammonia. Edinburgh.-Water of

monia.

Take of muriate of ammonia one pound, line newly burnt one pound and a half, distile water one pound, water nine ounces. Upon the lime broken to pieces pour the water in an i or earthen vessel, cover it up until the lime ha fallen into powder and become cold; then rub the muriate to a fine powder, and triturate it wi lime in a mortar, after which put them direct into a bottle glass retort. Place the retort in sand-bath and adapt to it a receiver furnished with a tube passing into a phial containing the distilled water; the phial, however, being suff ciently large to hold double the quantity water. Then apply the fire, gradually raising until the bottom of the iron pot be red hot, and so long as gas and vapor are produced. The spe cific gravity of this solution is 0.939.

The muriate of ammonia in these processes is decomposed by the lime, this last having a greater affinity for the acid than has the amme nia; the ammonia is consequently disengaged and passes over, and the product is an aqueous

solution of it.

Qualities.-Ammonia in this liquid form is colorless fluid, very pungent in its odor, and having an extremely acid taste. It unites with all the acids and forms with them neutral salts It soon becomes carbonated by mere exposure to the atmosphere. Acids and metallic salts and alum are incompatible with it in prescriptions. When it is at all carbonated the presence of the carbonic acid may be detected by adding to s of the solution muriate of lime, which will form a precipitate; if indeed it at all effervesce with

acids the presence of carbonic acid may be inferred.

Medical properties.-Stimulant, antacid, and Erubefacient. Dose from mx to mxx. If taken as a poison and death does not immediately ensue considerable quantities of vinegar should be 5 poured down the throat.

Aqua ammonia diluta. Edinburgh.-Distilled water of ammonia.

Take of water of ammonia one part, distilled water two parts. Mix them.

As extemporaneous dilution is always sufficiently easy, this preparation might have been dispensed with.

Liquor ammonia acetatis. London.-Solution of acetate of ammonia.

Take of subcarbonate of ammonia two ounces, diluted acetic acid four pints or a sufficient quantity. Add the acid to the subcarbonate of ammonia until the effervescence cease.

Aqua acetatis ammonia. Edinburgh.-Water of acetate of ammonia.

Take of carbonate of ammonia in powder any quantity, pour upon it so much weak acid as will exactly saturate the ammonia.

It is better, perhaps, that the saturation be made by guess and taste, and then tasted as in the Dublin College; for the distilled vinegar is always of varied strength.

Qualities. This liquor is limpid and nearly without color. Strong acids and fixed alkalies decompose it, as do alum, magnesia, lime water, sulphate of magnesia, oxymuriate of mercury, and nitrate of silver, which are all of course incompatible with it in prescription. The sulphates of metals and acetate of lead are also decomposed by it.

Medical properties.-An exceedingly useful refrigerant and diaphoretic in disorders accompanied by much febrile heat. It is also diuretic, especially when taken while the patient is not in bed. It is useful as a cooling lotion to the head in cases of phrenitic affection, and Dr. Thomson tells us that he has employed it with the best effect, as a lotion in porrigo affecting the scalp. Dose from f. 3iij to f. 3j.

Liquor ammonia subcarbonatis. London.Solution of subcarbonate of ammonia.

Take of subcarbonate of ammonia four ounces, distilled water a pint. Dissolve the subcarbonate of ammonia in water, and filter through paper.

Solutio subcarbonatis ammonia. Edinburgh. Solution of subcarbonate of ammonia.

Take of subcarbonate of ammonia one part, distilled water four parts. Dissolve the subcarbonate in the water, and filter through paper. Qualities.-Limpid and colorless; it forms a coagulum, when shaken with twice its bulk of alcohol.

Medical properties.-Stimulant and diaphoretic. Dose from mxxv. to f. 3j. in any fluid that does not decompose it.

PREPARATIONS OF POTASSA. Liquor potassa. London.-Solution of potassa. Take of subcarbonate of potassa a pound; lime fresh burnt half a pound; boiling distilled water a gallon. Dissolve the subcarbonate of

Add the re

potassa in two pints of the water. mainder of the water to the lime; mix the hot liquors together; then set the mixture aside in a covered vessel; and, when it is cold, let it be strained through a cotton bag. If, on the addition of any diluted acid, effervescence be excited, more lime must be added, and the filtration repeated. A pint of this solution ought to weigh sixteen ounces.

Aqua potassa. Edinburgh.-Water of potassa. Take of lime fresh burnt eight ounces; subcarbonate of potassa six ounces; boiling water twenty-eight ounces. Let the lime be put into an iron or earthen vessel with twenty ounces of the water. When the ebullition ceases, immediately add the salt dissolved in the remaining eight ounces of the water; and, having thoroughly mixed the whole, cover the vessel till the mixture cool. The mixture being cooled, agitate it well, and pour it into a glass funnel, the tube of which is obstructed with a piece of clean linen. Cover the upper orifice of the funnel, while its tube is inserted into another glass vessel, that the solution of potassa may gradually drop through the linen of the lower vessel. When it first ceases to drop, pour a few ounces of water into the funnel; but cautiously, so that the fluid may swim above the matter. The water of potassa will again begin to drop. The affusion of water, however, must be repeated until three pounds have filtered, which will be in the space of two or three days; then let the upper part of the solution be mixed with the lower by agitation, and preserve it in a well stopped vessel.

In this separation the lime, attracting the carbonic acid of the subcarbonate of potassa, leaves the alkali in a state of purity, or causticity. The liquid should be kept in closely stopped bottles, otherwise it will become carbonated by exposure to the air.

Qualities.-Solution of potassa is exceedingly caustic, scarcely admitting of being put on the tongue. It is without color, and has an oily appearance when shaken. If muriates be present in it they may be detected by saturating a portion of the liquid with nitric acid, then adding nitrate of barytes to precipitate the sulphates if any; and lastly adding a solution of nitrate of silver, which is precipitated if any muriate be present. Sulphates are detected by saturating the liquor with muriatic acid, and adding muriate of barytes; and if lime be present blowing into a liquor through a tube, by adding carbonic acid, will render it turbid. It is always more or less impure, as ordered by the pharmacopoeias, but not to the extent of interfering with its medicinal virtues. The specific gravity of the solution ought to be 1.056. It is a solvent of gum, extractive and resin, and it forms soap when mixed with oils or fat.

Medical properties.-Diuretic, antacid, and lithontriptic. Dr. Willan speaks highly of it in lepra; and Dr. Thomson says that it may be almost regarded as a specific in the various species of psoriasis which depend altogether upon acidity in the primæ viæ, and a hasty and consequently imperfect formation of the juices of the stomach.

Dose mx. to f. 3j. or f. 3ij in some of the cutaneous affections.

Liquor potasse subcarbonatis. London.-Solution of carbonate of potassa.

Take of subcarbonate of potassa a pound; distilled water twelve fluid ounces. Dissolve the subcarbonate of potassa in the water, and filter the solution through paper.

Qualities. This solution ought to be quite clear, and without color or smell. It is of course incompatible in prescription with sulphate of magnesia and the metallic salts. It is likewise improper to mix with lime water, or magnesia, or substances containing much of the tannin principle.

Medical properties.-The same as the salt itself. Dose from mxv. to f. 3ij.

Potassa cum calce. London.-Potassa with lime. Take of solution of potassa three pints; lime fresh burnt a pound. Boil the solution of potassa down to a pint; then add the lime, previously slaked by the water, and intimately mix them.

Potassa cum calce. Olim, Causticum commune mitius. Edinburgh.-Potassa with lime; formerly, milder common caustic.

Take of the water of potassa any quantity. Evaporate it to one-third part in a covered iron vessel; then mix with it as much newly slaked lime as will bring it to the consistence of a solid paste, which is to be preserved in a well stopped vessel. The lime makes the alkali less deliquescent, and consequently more manageable as an escharotic.

Potassa fusa. London.-Fused potassa.

Take of solution of potassa a gallon. Evaporate the water in a clean iron vessel over the fire until, the ebullition having ceased, the potassa melts; then pour it out upon a clean iron plate into pieces of proper form.

Potassa. Olim. Causticum commune acerriEdinburgh. Potassa; formerly stronger

тит.

common caustic.

Take of solution of potassa any quantity. Evaporate it in a covered very clean iron vessel until, the ebullition being over, the saline matter flows smoothly like oil, which happens before the vessel becomes red hot. Then pour it out upon a clean iron plate, cut it into small masses before it hardens, and let it be preserved in well stopped phials.

The concrete potassa procured by these processes is a hydrate sufficiently pure for medical purposes; but it still contains the same foreign ingredients as the solution. To procure it as free as possible from carbonic acid, the evaporation should be performed in a silver vessel very quickly; the vessel should be deep, so that the watery vapor which arises may exclude the atmospheric air. It is generally run into moulds, and formed into solid cylinders, which are covered with paper, and kept in well stopped bottles. The method of Berthollet for obtaining it in perfect purity, which is usually described in chemical and pharmaceutical works, is too troublesome and expensive to be generally adopted. The following method, proposed by Lowitz, is

more economical:

A solution of potassa must be evaporated till a pellicle forms on its surface, then allowed to cool; and the saline deposit, which consists

cniefly of the foreign salts, carefully separate! The evaporation is then to be renewed, skimaiy off the pellicles that form on the surface of t fluid, which, as soon as these cease to be pr duced, and the ebullition is ended, must be moved from the fire, and constantly stirred t it is cold. The mass is next to be dissolved twice its weight of distilled cold water, the se lution filtered and evaporated in a clean iron silver basin until crystals are deposited. If th heated fluid consolidate into a mass in any gree, a small portion of water must be adde and the mass again heated to fluidity. Th supernatant liquor is left of a brown cok which, after being kept for some time at rest well-stopped phials, deposits the coloring matz and may again be evaporated and crystallised a before. The crystals obtained in the vanco evaporations are colorless, pure potassaThomson.

Qualities. When made properly, potasst s in the form of a white brittle substance, smella like quicklime when being slaked, and too catic to be tasted. It is soluble in water an alcohol, and attracts humidity from the air. I is fused and volatilised by heat; and it combine with sulphur, the fixed oils, and the metal oxides.

Medical properties.-Escharotic. Employe usefully in strictures requiring caustic.

Potassa acetas. London.-Acetate of potass Take of subcarbonate of potassa a pound a a half; of the stronger acetic acid two p boiling distilled water two pints. Mix the a with the water, and pour it upon the subcarbon of potassa till all ebullition cease, after win filter. First evaporate the solution in a wate bath until no more bubbles rise; then exp it to gradually increased heat, and continue evaporation till a pellicle form, which shoud be removed and dried on blotting paper. peat the evaporation again and again, remorus the pellicles as they form, and drying them the manner already described.

Acetas potassa. Edinburgh.-Acetate of p tassa.

Take of very pure carbonate of potassa on pound; weak acetic acid a sufficient quantity Boil the subcarbonate in five pounds of the ac and add more acid at different times, until, the watery part of the former portion being nearly dissipated by evaporation, the acid newly added occasions no effervescence, which will be the cas when about twenty pounds of it have been co sumed; then evaporate slowly to dryness. L quefy this impure salt with a gentle heat for short time; then dissolve it in water, and filter through paper. If the liquefaction have bee properly performed, the filtered fluid will be limpid, but otherwise of a brown color. After wards evaporate this fluid in a shallow glass vessel, so that, when removed from the fire, if may pass into a crystalline mass. Finally, the acetate of potassa ought to be preserved in closely shut vessels.

Qualities. This salt possesses a peculiar oder and a sharp taste. It is deliquescent, and it changes into a subcarbonate by exposure to a red heat. It is soluble in water and alcohol.

When adulterated with tartrate of potassa a preecipitate will be occasioned by the addition of tartaric acid in solution; and acetate of lead will produce a precipitate soluble in acetic acid, sulphates may be diluted by nitrate of barytes, and muriates by nitrate of silver.

Medical properties.-Aperient and diuretic. Principally employed in dropsical affections. Dose as an aperient two or three drachms-as a diuretic, from half a drachm to a drachm often repeated.

Potassa carbonas. London.-Carbonate of potassa.

Take of the solution of subcarbonate of potassa a gallon. By means of a proper apparatus transmit carbonic acid through the solution until it is saturated. Then filter. Evaporate until crystals form, being careful not to increase the heat above 120°, separate the crystals from the fluid and dry them on blotting paper.

Carbonic acid is easily obtained from white marble and diluted sulphuric acid.

Carbonas potassa. Edinburgh.-Carbonate of potassa.

Take of pure carbonate of potassa two parts, water three parts. Dissolve the salt in the water, and by means of a proper apparatus throw into it a stream of carbonic acid gas. Filter the solution when it ceases to absorb the acid, and then evaporate it by a heat not exceeding 180°, that crystals may form.

The carbonic acid is easily obtained by pouring diluted sulphuric acid on pulverised carbonate of lime.

It has been recommended by some that muriatic acid be used to evolve the carbonic acid from the marble.

Qualities.—This salt, prepared by these formula, is, properly speaking, a bicarbonate; the subcarbonate of the pharmacopoeias being really a carbonate.' It is without odor, has a taste slightly alkalescent, and mild. It is not soluble in alcohol. It is incompatible in prescriptions with the acidulous salts, with the metallic salts, with borax, muriate of ammonia, lime water, sulphate of magnesia, and alum.

Medical properties.-Useful in the preparation of the effervescing draught. Dose of the salt from 9fs to 3j.

Potasse subcarbonas. London.-Subcarbonate of potassa.

Take of impure potassa (pearl ashes), reduced to a powder, three pounds, boiling water three pints and a half. Dissolve the potassa in the water and filter; then pour the solution into a clean iron pot and evaporate with a gentle heat until the liquor thicken; lastly, being taken from the fire, stir assiduously with an iron spatula until the salt concrete in small grains.

A purer subcarbonate of potassa may be prepared in a similar manner from tartar, previously

burnt until it be of an ash color.

Subcarbonas potassa. Edinburgh.-Subcarbonate of potassa.

Let impure carbonate of potassa be put into a crucible and exposed to a red heat. Then triturate it with an equal weight of water. Pour the solution after the impurities have subsided into a clean iron pot, and boil it to dryness; VOL. XVII.

stirring the salt constantly towards the end of the boiling, to prevent it from adhering to the vessel.

This salt, as above intimated, is rather a carbonate than a subcarbonate, 'being composed of one atom of each of its components.' See CHE

MISTRY.

Subcarbonas potassa purissimus. Edinburgh.Pure subcarbonate of potassa.

Take of impure supertartrate of potassa any quantity, wrap it up in moist bibulous paper, or put it into a crucible; and, having placed it among live coals, let it be burnt to a black mass; which, after having reduced it to powder, expose in an open crucible to a moderate fire, until it become white, or at least ash-colored, taking care that it be not melted. Then dissolve it in warm water; strain the solution through a linen cloth, and evaporate it in a clean iron vessel, stirring constantly towards the end of the process with an iron spoon, lest any of it should adhere to the bottom of the vessel. A very white salt will remain, which is to be left a little longer on the fire till the bottom of the vessel become red hot. Finally, when it is cold let it be preserved in well-stopped glass vessels.

Qualities.-The same as those obtained from the potassa of commerce, with fewer impurities. The impurities of this salt we are directed to ascertain in the following manner :-'If one part of it be dissolved in eight parts of distilled water, and saturated with pure nitric acid, the presence of siliceous earth will be indicated by the solution becoming turbid, and, by weighing the precipitate, its quantity may be ascertained. A precipitate being formed on the addition of muriate of barytes indicates the presence of the sulphates; a white precipitate turning bluish on exposure to the light, on adding nitrate of silver, proves the presence of muriatic salts; and calcareous earth is rendered evident by dropping into a solution of the subcarbonate a few drops of a solution of oxalic acid or oxalate of ammonia.'

Medical properties.-Antacid and diuretic; principally employed in the composition of the saline draught, in the proportion of a scruple to a table spoonful of lemon juice, or fifteen grains of the concrete tartaric acid.

Potasse sulphus. London.-Sulphate of po

Dr. Thomson prefers the Edinburgh process as being quite equal to the others with less ex

pense.

Qualities. The taste is nauseous and rather bitter. The crystals decrepitate when heated, but they are not efflorescent. They are soluble to a certain extent in water. The nitric, muriatic, and tartaric acids partially decompose it: its solution is also incompatible in prescription with muriate of barytes, muriate of lime, oxymuriate of mercury, nitrate of silver, and acetate of lead.

Medical properties.-Cathartic and deobstruent. It is often combined with rhubarb and given in the form of powder, on account of its being less soluble and deliquescent than some other of the saline purgatives. Some practitioners, as Dr. Yeats, have much lauded it in complaints of children. Dr. Y. recommends it to be very finely powdered. Dose for an adult from 15 grs. to 3j.

Potassa supersulphas. London.-Supersulphate of potassa.

Take of the salt which remains after the distillation of the nitric acid two pounds, boiling water four pints. Mix them so that the salt may be dissolved, and filter. Then let the solution be boiled till one half is evaporated, and let it be set aside to crystallise. Pour off the water, and let the crystals be dried on bibulous paper.

Qualities. The crystals are acid and bitterish, soluble in water, and reducible to simple sulphate of potassa by exposure to a red heat.

Medical properties.-It has been introduced into the pharmacopoeia from an idea that it will afford a useful means of producing the sulphuric acid in combination with an aperient salt. Dose 10 grs. to 3ij.

Sulphas potassa cum sulphure. Edinburgh.Sulphate of potassa with sulphur.

Take of nitrate of potassa in powder, and of sublimed sulphur equal weights. Mix them well together, and throw the mixture in small quantities at a time into a red hot crucible. The deflagration being finished, let the salt cool, and preserve it in a well-stopped glass vessel.

This preparation was originally known under the name of sal polychrest. In the process of making both sulphuric and sulphurous acids are formed from the sulphur, but the oxygen which is evolved by the heat is not sufficient to acidify all the sulphur employed, so that part of the latter goes into combination with the potassa of the nitre as sulphur. Thus, sulphate and supersulphate of potassa are formed together with a sulphuret of the same.

Qualities. The salt tastes acid, and reddens an infusion of litmus. It is soluble in water, and by exposure to air converted into sulphate of potassa.

Medical properties.-Cathartic, like the sulphate of potassa, by which last it is almost superseded.

Potassa tartras. London.-Tartrate of potassa. Take of subcarbonate of potassa sixteen ounces, supertartrate of potassa three pounds, boiling water a gallon. Dissolve the subcarbonate of potassa in the water, and add the supertartrate of potassa reduced to powder, till the

effervescence cease. Filter the solution throng! paper; then boil it until a pellicle appear on surface, and set it aside to crystallise. The water being poured off from the crystals let the be dried on bibulous paper.

Turtras potassa. Edinburgh.-Tartrate of p tassa:

50

Take of subcarbonate of potassa one part, pertartrate of potassa three parts, or a suficie quantity, boiling water fifteen parts. To th subcarbonate dissolved in the water add in sm portions the supertartrate of potassa reduced t: | fine powder so long as it excites effervescence, which gradually ceases before three times t weight of the subcarbonate of potassa be adde Let the solution when it is cool be filtered, en porated, and set aside to form crystals.

Qualities. This salt is bitterish to the taste; is soluble in water, and deliquescent. Th weaker acids partially decompose it; and water, magnesia, muriate of barytes, nitrate si silver, and acetate of lead completely.

Medical properties.-A useful purgative, rating without griping. Dose from f. 3ij. to £ Aqua supercarbonatis potassa. EdinburghWater of supercarbonate of potassa.

Take of water ten pounds, pure subcarbon of potassa one ounce. Dissolve and expose th solution to a current of carbonic acid gas, aris from carbonate of lime in powder three orna sulphuric acid three ounces, and water thre pounds, gradually and cautiously mixed. T chemical apparatus of Dr. Nooth is well su for this preparation. But, if a large quantity the solution be wanted, an apparatus which wil admit of a sufficiently great pressure should employed. The solution must be preserved a well stopped vessels.

Qualities. Taste pungent and acidulous, n♪ lently effervescing with all acids.

Medical properties.-Antacid, diuretic, a lithontriptic. It is better for the saline drangh in effervescence, than that prepared with the cr bonate. Dose in calculous disorders f.viij. or three times a day.

PREPARATIONS OF SODA.

Soda carbonas, London.-Carbonate of seda Take of subcarbonate of soda a pound, dis tilled water three pints. Dissolve the subc bonate of soda in the distilled water. Then let carbonic acid be transmitted through the solution by means of a proper apparatus until it be st rated, and set it apart to crystallise. Dry the crystals by compressing them in blotting paper. Let the remainder of the solution be evaporated by a heat not exceeding 120°, in order that more crystals may be procured. These are to be compressed and dried in the same manner before.

Carbonas soda. Edinburgh.—Carbonate of

soda.

Take of subcarbonate of soda two parts, water three parts. Dissolve the salt in the water and until subject it to a stream of carbonic acid gas, the acid be no longer absorbed. Then let the fluid be filtered and evaporated in a heat not ex ceeding 18°, so that crystals may form. The car bonic acid is easily obtained from equal weights