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state it has usually been hept by druggisis for the use of silve sinitiis, and was formerly also used in pharmacy under the litteof.Sal Enixum. On crystalliging, it chiesy fixes itself to theside of the vesset, Dom Which bed flender nee lles somelimes shoot. It has a strong acid taste, and reddens vegetableblues: one part is solubie in t vo of Water at 6O', and in tessthan an equat weight at 212', and it is not solubie in alkohol; it a rds a usesul means of exhibiting sulphuric acid combinedwith an opening sali in a solid form, an indication whicli is osten destrabie. It consists of 37 paris of sulphate os potasti, with 83 excess of acid.
Kali lariari tum, P. L. t 78 I. Tartarum solubile, P. L. 1745.
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Supertartrate os potasti contains os superabundant acid, whicli is here neutralized by the addition os subcarbonate os potassi, the cessation of effervescence being the test os saturation. Iis crystals are four equal-sided prisms, terminated by two-sided pyramids. Iis taste is somewhat bitter. One part is solubie in Dur os mater at 6O', and lience, compared with the sparingly solubie Super-tartrate, iis name of solubis tartar has been draWn. Potasti and tartaric acid have astronger disposition to Unite in the proportions of the supersali than of the neutral one; hence the addition os more tartaric acid forms a granular precipitate os super sali, and sodo the other actus also, With any of whicli there re it cannot be properly directed in prescription.
Dissolve the potasti in Water, and sit ter: then potar the solution into a clean iron pot
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KALIES AND THEIR SALTS. Si and evaporate the water OVer a moderate
sire, untii the liquor thicliens; then let thu fit ehe withdra via, and stir the liquor Constantly With an iron rod untii the sali concretus into
A purer sub carbonate of potasti may bo
prepared in the fame manner from turtur,
Previous to the Pharmacopoeia of 1745, the alhaline saltobtained Dom the asties of different vegetabies Was supposedio differ, and a great number of preparations os the fame,named after the particular plant Dom Whicli it Was obtained, mere directed to be hept. ordinary potasti is prepared by the incineration os various vegetabies, and is denominated in commerce by the place from Whicli it is imported, as Russian, American, &c. The only difference Whicli respecis the plant, is in the proportion of the athali yielded, and this extends also to the severat soris of potasti Whicli are found in the market: allos them contain heterogeneous matters in abundance, but indifferent quantities ; as sulphate and muriate of potasti, insolubie matter, &c. The proportion os pure potasti yielded by different soris, varies according to Vauquelin frona to
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Soon as a pellicle appeared. It has been thought that this part of the process whicli is connected with some labour and expence might be omitted, Ud that the fame effect would beproduced by using, in the first instance, only enough Water sorine solution of the more solubie subcarbonate. When thesolution has evaporated to about the consistence of cream, the proportion of Water Which rematris is necessary to the composition of the crystals ; the further evaporation is there- fore to be stopped by withdrining the fire, and the mixtureis to be stirred illi it concretes into crystalline grains. It is matter os absolute necessity that the iron pol should be cleanand Dee stom rust. This sali deliquesces, and there re requires to be kept in stopped botiles. 'Tartar consists of supertartrate of potasti, mixed mitti se er heterogeneous matters than common potasti. Thisacid, lihe the other vegetable acidf, may be Wholly de- composed by a strong heat, and a subcarbonate os potasti rematris coloured by carbone. Trealed by the fame processas the former, this yields a purer but more expensive sali,
and is directed to be hept as being preserable sor many
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CARBONATE OF POTASH. Tahe of Subcarbonate of Potasti prepared frona Tartar, R POund. Carbonate of Ammonia, three
Distilled Water, a Pint. Having previ ousty dissolved the potasti in
the water, add the Carbonate os ammonia: then hy means os a sanit buth apply a heatos 48o' for three ho urs, or untii the ammoniashali he driven Osr: lastly, set the Solution byto crystallige. The rema ining solution maybe evapora ted in the Same manner, that Cry-Stal S may again sorin When it is set by.
This process Was invented by Berthollet. TLe potastitahes the carbonic acid Dom the ammonia, whicli is volatile, and passes off in the temperature employed; it is ho eververy dissiculi ho delach the ammonia entirely. The potasbis saturaled With carbonic acid, and contains double the quantity that the sub-sali does, whicli proportion it gives Out Onine addition os muriatic acid, and it may be converted again
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than the former; it crystalliges, and does not deliquesce. Itis solubie in about Dur times iis Reight of water at the common temperature, and in illis of iis meight at 212', but this Ialter heat delaches some of the carbonic acid.
Aqua latis parati, P. L. 1787. Lixivium tartari, P. L. 1765. Oleum tartari per deliquium, P L. I 720.
Dissolve the subcarbonate os potasti in themater, and then Strain the solution through
pa Per. This ij a more definite preparation than the aqua hali praeparati of the Pharmacopoeia os 1 8 , and it also differs hom it; fori during the exposure necessary for deliquescence in the lalter, carbonic acid as Weli as moisture Was
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attraeten Dom the air. The solution here directed wili, in the ordinary state of the subcarbonate, amount to nearly eighteen ounces in bulla.
A qua tali puri, P. L. 1787. Lixivium saponarium, Ρ. L.
Boiling distilled Water, a gallon. Dissolve the potasti in t vo pinis of the
mater. Add the remaining Water to the lime. Mix the liquors While they are hol, Stirthem together, then set the mixture by in acovered vesset, and , after it has cooled, strain the solution through a Cotton bag. Is any diluted acid dropped into the sol Ution occasion the extrication os bubbles of gas, it Will be necessary to add more limeand to stratia it again. A pint of this solution ought to Weigh fixteen OunCCS.
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Vnien carbonate os potasti and lime are thus mixed, thelime unites to the carbonic acid and forms an insolubie carbonate of lime, and the potasti remains in solution. The
proportion os lime here directed, is, is it be good, sussicient
for the perfect decomposition of the sali, and there is an ad-vantage in not having a greater residuary mass than is necessary. The precipitate os carbonate of lime retains, bycapillary attraction, n early of the solution Os potasti, and
this may be disiodged by cautiousty pouring upon the sur- face an equat quantity of Water, Which being lighter ilian thesolution itself, Will not mix With it untii the n eater part of the lalter has passed the fiter. At every period of the process, the presence of external air should he avoided, as afford- ing a supply of carbonic acid; and calico, as here directed, both fillers more quichly than any other means, and is notacted upon by the potasti. The purity of the solution should always be tried by the addition os lime Water, Whicli, is therebe any combined carbonic acid, Will denote it by a precipitate. It is also possibie that a superabundance of lime may have been used, and that lime and potasti may both bo dissolved; this is discoverable and removable the Same Way, by droppingin the solution os subcarbonate of potasti. This solution is
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Tahe of Solution of Potasti, a gallon.
Evaporate the water in a clean iron potover the sire; untii, when the ebullition has Cea Sed, the potasti rem nins in a State of fusion ; pour it upon a Clean iron plate, intopieces of convenient sol m.
This preparation is suffciently pure for iis use as a cautery, much more indeed so than the former hali purum; itcannot be obtained in a state pure enough for accurate experimenis, eXcept by a solution of it in alkohol, separationof the undissolved salis, and a second evaporation, accordingto Berthollet's process Ioiarn. du Phy. V. xxviii.). The cessation of ebullition is suffcient proos that the water is evaporaled, and it may, When poured upon the iron plate, bereadi ly divided, besore it seis, into smali pieces of convenient si Ze, or run into moulds of the shape it may be wished to give it. Is heated it fuses, and again concretes as it cools ; it destroys animal matter rapidly, and is applied as a caustic. It deliquesces on expostare, and one part of water Will dissolve two os it.
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Calx cum hali puro, P. L. II87. Causticum commune fortius, P. L. 1745. Lapis infernalis sive septicus, P. L. Ι72O.
Τake of Solution of Ρotasti, three pinis. Fresti Lime, a POUnd. Boii tho solution of potasti do vn to a pint, then add the lime, previousty sta ked by the addition of water, and mix them together intimately.
This mechanical admixture forms the common caustici whicli is convenient and more manageable in iis operationthan the potasti alone. The lime gives consistence to thesolution os potasti, and this consistence, as it prevenis thepotasti Dom spreading, regulates the boundaries of iis actionon the part lo Whicli it is applied.