Sulphuretum potassæ, Edin. sulphuret of potash, liver of sulphur.

Tartris potassæ, tartrite of potash, Edin. soluble tartar, tartarised kali, Lond.

Carbonas soda, carbonate of soda, Edin. prepared natron, Lond.

Phosphas soda, Edin. phosphate of soda. Murias soda, muriate of soda, sea salt. Sulphas soda, Edin. sulphate of soda, natron vitriolatum, Lond. Glauber's salt.

Tartris soda, Edin. tartrite of soda, natron tartarisatum, Lond. Rochelle salt.

Carbonas calcis præparatus, prepared chalk, Lond. carbonate of lime, Edin. Phosphas calcis, Edin. phosphate of lime, burnt hartshorn, Lond.

Carbonas magnesiæ, Edin. magnesia alba, Lond. Dubl. carbonate of magnesia.

Phosphas calcis, Edin. magnesia usta, Lond. burnt or calcined magnesia.

Sulphas aluminæ exsiccatus, Edin. dried sulphate of alumine, burnt alum, Lond.

In the Dublin process for making magnesia there is a mutual decomposition of the two salts employed. The potash unites itself to the sulphuric acid, while the carbonic acid combines with the magnesia.

The large quantity of water used is necessary for the solution of the sulphate of potash formed; and the boiling is indispen sably requisite for the expulsion of a por. tion of the carbonic acid, which retains a part of the magnesia in solution. Sulphate of Potash may be obtained from the liquor which passes through the filter, by evapo ration. This is not pure, however, but mixed with undecomposed carbonate of potash for one hundred parts of crystallized carbonate of potash are sufficient for the decomposition of one hundred and twenty-five parts of sulphate of magnesia ; and as the carbonate of potash of commerce contains a larger proportion of alkali than the crystallized carbonate, a still less proportion should be used. From these quantities about forty-five parts of carbo nate of magnesia are obtained.

The ablutions should be made with very pure water; for nicer purposes distilled water may be used, and soft water is in every case necessary. Hard water for this

Aqua carbonatis ammonia, Edin. water of carbonate of ammonia.

Aqua acetitis ammonia, Edin. water of acetite of ammonia, spirit of mindere

principle in waters, giving the property called hardness, is generally a salt of lime, which decomposes the carbonate of magnesia, by compound affinity, giving rise to carbonate of lime, while the magnesia unites itself to the acid of the calcareous salt, by which the quantity of the carbo nate is not only lessened, but is rendered lime. Another source of impurity is the impure by the admixture of carbonate of

silica which the sub-carbonate of potash generally contains. It is most easily got rid of by exposing the alkaline solution to the air for several days before it is used.

Murias baryta, muriate of baryte, Edin. Aqua calcis, lime water, Edin. Lond. Dubl.

carbonic acid, the silica is precipitated, and may be separated by filtration.

The carbonate of magnesia thus prepared is a very light, white, opaque substance,

without smell or taste,effervescing withacids. It is not, however, saturated with carbonic acid. By decomposing sulphate of magne sia by an alkaline carbonate, without the application of heat, carbonate of magnesia is gradually deposited in transparent, brilliant, hexagonal crystals, terminated by an oblique hexagonal plane, and soluble in about four hundred and eighty times its weight of water. The crystallized carbonate of magnesia consists of fifty acid, twenty-five magnesia, and twenty-five water; the sub-carbonate consists of fortyeight acid, forty magnesia, and twelve water; and the carbonate of commerce of thirty-four acid, forty-five magnesia, and twenty-one water. It is decomposed by all the acids, potash, soda, baryte, lime, and strontian, the sulphate, phosphate, nitrate, and muriate of alumina, and the super-phosphate of lime,

Sulphur præcipitatum, Lond, precipi tated sulphur.

In preparing this last, instead of dissolv. ing sulphuret of potash in water, we may gradually add sublimed sulphur to a boiling solution of potash, until it be saturated. When the sulphuretted potash is thrown into water, it is entirely dissolved, but not without decomposition, for it is converted into sulphate of potash, hydroguretted sulphuret of potash, and sulphuretted hydroguret of potash. The two last compounds are again decomposed on the addition of any acid. The acid combines with the pot. ash, sulphuretted hydrogen flies off in the form of gas, while sulphur is precipitated. It is of little consequence what acid is employed to precipitate the sulphur. The London College order the sulphuric; while the Dublin College use nitrous acid, probably because the nitrate of potash formed is more easily washed away than sulphate of potash.

Precipitated sulphur does not differ from well-washed sublimed sulphur, except in being much dearer. Its paler colour is ow. ing to its more minute division, or, accord. ing to Dr. Thomson, to the presence of a little water; but from either circumstance

it derives no superiority to compensate for the disagreeableness of its preparation.

These are all the more simple preparations of sulphur in common use. There are various preparations into which sulphur enters as an ingredient; but such as constituting compounds of the general nature of metals, alkalies, oils, &c. will be found under those classes.

CLASS V. Metallica. METALLINE PREPA

RATIONS.

The metalline prepartions are very numer. ous, especially those of antimony and quicksilver.

Sulphuretum antimonii præparatum, Edin. prepared antimony.

Oxidum antim. cum sulphure per nitratem potassæ, Edin. crocus of antimony, Lond.

Oxidum antimonii, cum sulphure, vitrificatum, vitrified antimony, Lond. glass of antimony.

Sulphuretum antimonii præcipitatum, precipitated sulphuret, or sulphur of antimony, Lond.

Murias antimonii, Edin. muriated anti

mony, Lond. butter of antimony.

Oxidum antimonii cum phosphate calcis, Edin. pulvis antimonialis, Lond. antimonial powder.

Tartris antimonii, tartarised, or tartrite of antimony.

Vinum tartritis antimonii, Edin. tartar emetic, antimonial wine, Lond.

Nitras argenti, Edin. argentum nitratum, Lond. nitrate of silver, lunar caustic. Ærugo præparata, Lond. Dub. prepared verdigrease, or carbonate of copper. Solutio sulphatis cupri composita, Edin. styptic water.

Ammoniaretum cupri, Edin. ammoniacal

copper.

Aqua cupri ammoniati, Lond. water of the same.

Ferri limatura purificata, Edin. purified iron filings.

Carbonas ferri, Edin. rubigo ferri, Lond. carbonate, or rust of iron.

Sulphas ferri, Edin. vitriolated iron, Lond. sulphate of iron.

Tinctura muriatis ferri, tincture of muri ate of iron, Lond.

Murias ammoniæ et ferri, martial flowers, ammoniacal iron, Lond.

Tinctura ejusdem, tincture of the same. Tartris ferri, tartrite of, or tartarised, iron, Lond.

Vinum ferri, Lond. wine of iron.

Hydrargyrus purificatus, Lond. purified quicksilver.

Acetis hydrargyri acetite, Edin. of quick silver.

Murias hydrargyri, Edin. Lond. muriate of quicksilver, corrosive sublimate.

Submurias hydrargyri, Edin. calomel, Lond.

tion always similar in its composition and properties. He has led to this proposal by considering the uncertainty of the applica tion, and the precarious nature of the agency of fire, by which means a variable portion of the oxide of antimony may be volatalised, and that which remains may be oxydized in various degrees.

M. Chenevix, therefore, proposes to prepare a substitute for James's powder by

Oxydum hydrargyri rubrum, Edin. red precipitate.

Subsulphas hydrargyri flavus, Edin. vitriolated quicksilver, Lond.

Sulphuretum hydrargyri nigrum, Edin. æthiops mineral, turpeth mineral.

Hydrargyrum sulphuratum nibrum, Lon. Dub. factitious cinnabar.

Acetis plumbi, Edin. acetite of lead, sugar of lead.

Aqua lithargyri acetata, Lond. extract of lead.

Cerussa acetata, Lond. acetated ceruse. Stanni pulvis, Lond. powder of tin. Oxydum zinci, Edin. oxide of zinc, calcined zinc. Lond.

Carbonas zinci, Edin. impurus præparatus, prepared calamine.

Oxydum zinci impurum præparatum, Edin. prepared tutty.

Sulphas zinci, Edin. vitriolated zinc, Lond.

The antimonial powder of the London College is supposed to be nearly the same with the celebrated nostrum of Dr. James, the composition of which was ascertained by Dr. Pearson of London, to whom we are also indebted for the above formula.

By burning sulphuret of antimony and shavings of hartshorn in a white heat, the sulphur is entirely expelled, and the antimony is oxydized, while the gelatine of the hartshorn is destroyed, and nothing is left but phosphate of lime, combined with a little lime. Therefore the mass which results is a mixture of oxide of antimony and phosphate of lime, which corresponds, at least, as to the nature of the ingredients, with James's powder, which, by Dr. Pearson's analysis, was found to consist of 43 phosphate of lime, and 57 oxide of antimony. Another excellent chemist, M. Chenevix, has lately proposed a method of forming the same combination in the humid way, with the view of obtaining a prepara

muriate of antimony and of phosphate of

muriatic acid, and then pouring this solution gradually into water sufficiently alkalized with ammonia. For the reason mentioned in the preceding article, it is absolutely necessary that the muriatic solution be poured into the alkaline liquor. By an opposite mode of procedure, the precipitate would contain more antimony at first, and towards the end the phosphate of lime would be predominant, and the antimony would be partly in the state of a submuriate. The phosphate of lime is most conveniently obtained pure by dissolving calcined bone in muriatic acid, and by precipitating it by ammonia. If the ammonia be quite free from carbonic acid, no muriate of lime is decomposed. M. Chenevix also found that his precipitate is entirely soluble in every acid which can dissolve either phosphate of lime or oxide of antimony sepa rately, and that about 0.28 of James's pow. der, and at an average 0.44 of the pulvis antimonialis of the London Pharmacopoeia resist the action of every acid.

CLASS VI. Olea Fixata. FIXED Oils.

These oils are improperly denominated expressed, which is their usual characteristic name, as in some instances they are obtained without expression, and in other instances expression is employed to obtain volatile oils. The Edinburgh college have therefore distinguished these different classes of oils by the terms fixed and volatile, which accurately characterize them.

Fixed oil is formed in no other part of vegetables than in their seeds. Sometimes, although very rarely, it is contained in the parenchyma of the fruit. Of this, the best known example is the olive. But it is most commonly found in the seeds of dicotyledonous vegetables, sometimes also in the fruit of monocotyledonous plants, as the cocos butyracea. It has various degrees of consistency, from the tallow of the croton sebiferum of China, and the butter

they have sent forth any flowers; and others, as thyme, when the flowers have just appeared. All fragrant herbs yield a larger proportion of oil, when produced in dry soils and in warm summers, than in opposite circumstances. On the other hand, some of the disagreeable strong-scented ones, as wormwood, are said to contain most oil in rainy seasons, and when growing in moist rich grounds,

Several chemists have been of opinion, that herbs and flowers, moderately dried, yield a greater quantity of essential oil, than if they were distilled when fresh. It is, however, highly improbable, that the quantity of essential oil will be increased by drying; on the contrary, part of it must be dissipated and lost. But drying may some times be useful in other ways; either by diminishing the bulk of the subject to be distilled, or by causing it to part with its oil more easily.

The choice of proper instruments is of great consequence for the performance of this process to advantage. There are some oils which pass freely over the swan-neck of the head of the common still: others, less volatile, cannot easily be made to rise so high. For obtaining these last, we would recommend a large low head, having a rim or hollow canal round it: in this canal, the oil is detained in its first ascent, and thence conveyed at once into the receiver, the advantages of which are sufficiently obvious.

With regard to the proportion of water to be employed; if whole plants, moderately dried, are used, or the shavings of woods, as much of either may be put into the vessel, as, lightly pressed, will occupy half its cavity; and as much water may be added as will fill two thirds of it. When fresh and juicy herbs are to be distilled, thrice their weight of water will be fully sufficient; but dry ones require a much larger quantity.

In general, there should be so much water, that after all intended to be distilled has come over, there may be liquor enough left to prevent the matter from burning to the still. The water and ingredients, altogether, should never take up more than three fourths of the still; there should be liquor enough to prevent any danger of an empyreuma, but not so much as to be apt to boil over into the receiver.

The subject of distillation should be macerated in the water until it be perfectly penetrated by it. To promote this effect, woods should be thinly shaved across the

grain, or sawn, roots cut transversely into thin slices, barks reduced into coarse pow der, and seeds slightly bruised. Very compact and tenacions substances require the maceration to be continued a week or two, or longer; for those of a softer and looser texture, two or three days are sufficient; while some tender herbs and flowers not only stand in no need of maceration, but are even injured by it. The fermentation which was formerly prescribed in some instances, is always hurtful.

With regard to the fire, the operator ought to be expeditious in raising it at first, and to keep it up during the whole process, to such a degree only, that the oil may freely distil; otherwise the oil will be exposed to an unnecessary heat; a circumstance which ought as much as possible to be avoided. Fire communicates to all these oils a disagreeable impregnation, as is evident from their being much less gratefal when newly distilled, than after they have stood for some time in a cool place: and the longer the heat is continued, the greater alteration it produces in them.

The greater number of oils require for their distillation the heat of water strongly boiling: but there are many also which rise with a heat considerably less; such as those of lemon and citron peel; of the flowers of lavender and rosemary, and of almost all the more odoriferous kinds of flowers. We have already observed, that these flowers have their fragrance much injured, or even destroyed, by beating or bruising them; it is impaired also by the immersion in water in the present process, and the more so in proportion to the continuance of the im mersion and the heat; hence oils, distilled in the common manner, prove much less agreeable in smell than the subjects themselves. For the distillation of substances of this class, another method has been contrived; instead of being immersed in water, they are exposed only to its vapour. A proper quantity of water being put into the bottom of the still, the odoriferous herbs or flowers are laid lightly in a basket, of snch a size that it may enter into the still, and rest against its sides just above the water. The head being then fitted on, and the water made to boil, the steam, percolating through the subject, imbibes the oil, without impairing its fragrance, and carries it over into the receiver. Oils thus obtained, possess the odour of the subject in an exquisite degree, and have nothing of the disagreeable seent perceivable in those