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Mlime-stones contain sonae portion Os Other earthis they may, under these circumstances, Vitrisy, and form a coating overthe furface of the lumps, Whicti Will defend them Bom theaction os mater, and thus preverat their Staking or solution: lime, theresere, may thus be ove burni. The pieces ossione to be burnt should be as nearly as may be of equat siete. Is half iis Weight of Water M poured upon time, it sWelis and falis into a White poWder, much heat is evolved, and partos the water rises in steam; this is called flaked lime, and in this state it readily attaches carbonic acid frona the ala. When perfectly dry it may be Eept in botiles for any tenginos time unaltered; but to obviate any chance of iis betagimpure Dom the above cause, it is usualty directed to be em- Noyed neWου prepared. Lime ne ly staked, and lo Whichmore Water is added, ought not to effervesce on the ad dition os acid.
Aqua calcis, P. L. I 87. Aqua calcis simplex, Z L. 17 5. Aqua calcis, P. L. 1720.
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Lime is solubie in about 450 times iis Weight of Water, orlitile more than one grain in one fluidounce; hence the proportion here directed is much more than is required for thesaturation of the Water, but as the larger quantity allows more-over for any impurity contained in the lime, and as it is a che articie, the quantity used is there re of less importance. The process here adopted is simple, essicacious, and convenient, and by keeping the solution standing upon the limeit will always he saturaled, and the place of any crust os cambonate of lime whicli forms upon the furface, is exposed, willbe supplied Dom the lime, Whicli remains in a state ready sorsolution.
Creta praeparata, P. L. 17SI. P.L 1745. Creta, P. L. I 720
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ΕARTHS AND THEIR SALTS. IO 1 po viter into a large vesset fuit of Water, thenstir it, und after a Shori intervat, potir thesupernatant turbid solution into another
This is the most certain method of obtaining the poWderuniform and fine. The principie has long been adopted
for the preparation os other fine and equat powders of insolubie substances, as in the common manufacture of whiten-ing, and it was also e loyed in the early Pharmacopoeiae; it consisis in the longer suspension of the finer particles in Water, So that, after the subsidente of the coisser in the sestinstance, the uniform and very subile poWder Which remains longer suspended, may be collected as the produci of a secondsubsidence. In the previous mechanical division, or grind-
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Tahe of Sulphate of Magnesia, Subcarbonate of Ρotasti, of eacha potand. Water, three gallonS. Dissolve the subcarbonate os potasti in three pinis of the water, and stratn: dissolve also the sulphate os magnesia separateb in sve pinis of the water, and strain: then addine rest of the water to the lai ter solution,
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103it is the object to collect as Deo as possibie Dom the last. Hence, as sulphate os potasti requires a large proportion os mater sor iis solution, such a proportion is directed in the frit instance, and it is asterWarci Mil Washed with more. Is waterbe impregnated With carbonic acid gas it Will dissolve carbon te of magnesia, and lience the liquor is made to boit for thepurpose of delaching it. Is the tWo solutions be mixed cold, and the precipitate lest sex some days upon the fiter Without artificiat drying, many large and perfect crystals of carbonate of magnesia Will be formed in it. The subsequent heat by ich the powder is dried si uid not be great enouo todelach any of the carbonic acid. The present process willyield a pure and elegant preparation; iis form is that os a White poWder, eastly Diable, and, according to Fourcroy, is the base be fully saturaled with carbonic acid, as in the crystala for in iis ordinary form it is a subcarbonate), IO0
paris contatu carbonic acid 5O, magnesia 25, Water 25 ; andis not so saturaled, but in iis state os sub-sali, carbonic acid 8, magnesia 40, Waler 12. In commerce, the muriate of magnesia contained in theresiduary liquor aster the costalligation os muriate of sodafrom sea water is decomposed by a similar process, and yielcia large proportion of the ordinary magnesia of the markets.
I ake of carbonate of Magnesia, i Our Ounces, burn it in a very strong sire for tWo
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Ιt may be noted that a definite quantity has been proscribed here and in many other cases for the salie of precisiononly, and not as influencing the quali ty of the produci. It was the magnesia usta of the former Pharmacopoeia : but asthe term magnesia is correctly eXpreSsiVe of the pure earth, so it has been thought proper to apply it decidedir, although, in common language, the .ame term is most generallyappliod to the carbonate, and ths epithet calcinia is added tos Xpress the present preparation. The process depends uponthe expulsion of the carbonic acid of the carbonate by heatand in the form of gas, and hence the carbonate yields tess
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Flores sulphuris loti, P. L. 1787. '
Sublimed sulphur prepared upon a large scale containssome sulphuric acid, Which is evident to the taste, and these . directions are intended to wash it away. It is farther pro-Per, that sulphur, When washed, should be kept in closed vesseis rather than in an open drawer; lar in the laltersituation iis superior sursace manifestly becomes acid on
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Sulphur praecipitatuna, P. L. I 87. P. L. I 745. I ac Sulphuris, P. L. 1720.
Tahe of sublimed Sulphur, a POUnd. Fresti Lime, three Pound S. Boii the sulphur and lime together in mater, then stra in the Solution through paper, and dros in as much muriatic acid as may bene Cessary to precipitate the sulphur: Iastly, Wash this by repente i affusions of water uiatilit is tastelOSS.
In the Pharmacopoeia os II15 a sulphuret os lime was formed, and the sulphur precipitaled froin the solution bysulphuric acid; in that of I 87 sulphuret os potash was de- composed by the fame acid. The insolubie sulphate of lime could scarcely be Washed out stom the former, and the sulphate of potasti not without dissiculty from the lalter; boththere re contained admixtures of these salis, to whiph theyowed a good deal of their Whiter appearance. The presentprecipitate, frona the ready solubili ty of the muriate of lime, mill be only sulphur, but it Will be stili much whiter in iis appearance than Sublimed sulphur, either frum more minute
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division, or some other cause not Weli ascertained. It will, however, differ in no other respect Dom sublimed sulphur, and is there re omitted in both the Edinburgh and Dublin Pharmacopoeia; but as this circumstance of colour gives it anadvantage in the composition of oinimenis, so as a refinc-ment, rather than necessary agent in practice, it is hereretained.
Oleum sulphuratum, P. L. 1787. Balsamum sulphuris simplex, P. L. II45.
Tahe of Washed Sulphur, i Ur OunCOS. Olive Oil, a Pint. Having heated the oti in a very large iron poli add the sulphur gradu ally, and stir themixture aster each addition untii they have
Great care must be tinen that the vesset be sussiciently large to contain thrice the buth of the ingredients, and that the heat be not raised higher than iust to malle the ollhubble, for Without such care the mixture mill swell, bollo er, and inflame.
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Tahe of was hed Sulphur, an OUn Ce., Suhcarbona te of Potasti, sive
The object of this preparation is to render the sulphur solabis in materi Which these proportions so managed Willeffeci; the former process Was deficient in the directions forfusing the mixture, Whicli is necessary. A persect chemicat Sulphuret of potasEwould require the use of potasti, not iis subcarbonat 3 but this is not necessary sor the purposes Ospharmac' at may also be proper to state, that this preparation is unfit for the separation os sulphuretted hydrogen gas,on account of the carbonis acid li contains, and that this may he best-obtained 'frois sulphuret of iron and sulphuric acidmuch diluted. From .ibe .cΩlQur Of. thς compound resulting froni the union os potasti and sulphur it has been