CAR

CAR

( 26 0 )

cenftituent parts may be arranged as fol-lows :—

One hundred parts of the pungent carbonatof ammonia contain

Carbonic acid - - - ca ? 'Ammonia - - - - 16.25 ^°‘

Ammonia in excefs - - - 9.6Water ------- 20.2

100.0

When this is reduced to 50 parts, and hasbecome mild carbonat, all the excefs of am-monia appears to be volatilized, and half of thefaturated carbonat of ammonia, but lefs waterin proportion; and when thus reduced, the 50parts will therefore confift of about

Carbonic acid - - - 27 ?

Ammonia - - - - 8.15 ■“"

Water ------ 14.9

50.0

It lhould be mentioned that, according to Mr.Davy, the proportion of ammonia in the fub-limed carbonat, much depends on the heat ufedin the procefs, independent of any fubfequentvolatilization; b

Carbonat of ammonia precipitates all theearths from their folutions in acids except mag-nefia, which it only partially decompofes, at-tended with particular circurtiftances, mentionedunder carbonat of magnefta.

This fait is very foluble in all kinds of fpirits,and as readily rifes with them, as with water, indiftillation. Advantage is taken of this propertyin preparing many of the ammoniacal fpiritsand compounds ufed in pharmacy.

The ufe of the carbonat of ammonia is chieflymedicinal. The common dry fmelling falts forthe pocket confift of this fait a little fcented.

CARBONAT OF POTASH. Kohlenfauregemoachfalkali, Germ. Carbonate de Potajfe, Fr.

Potash. Pearlash . Gcmeine Pottafche.Calcinirte Pottafche , Germ. Salin. Potajfe, Fr.

Salt of Tartar. Wnnjleinlaugenfalz, Germ.Sel de Tartre, Fr.

In this article we fhall firft treat of the me-thod of procuring the vegetable fixed alkali, andthe different forms under which it appears incommerce and domeftic ufe, and fhall thennotice the preparation and characters of thatneutral fait properly called, according to the mo-dern chemical nomenclature, Carbonat of Potajh.

The vegetable fixed alkali was fo named bythe chemifts of the la ft and former ages, be-

caufe it was procured in large quantities fromvegetable fubftances, and was in no cafe fup-pofed to be of mineral origin. From certainlate analyfes, however, by Klaproth and otherable chemifts, it has been difcovered to enter,as an eflential ingredient, into the compofitionof leucite, lepidolite, and a few other minerals,which are by none fufpected of deriving theirorigin from organized bodies. But though theexiftence of potalh in a mineral ftate has beenthus demonftrated, yet it is fo fmall in quan-tity, and fo difficultly procurable, that all thevaft fupplies of this fubftance which civilizedlife requires; have as yet been entirely obtainedfrom the combuftion of vegetables.

If the woody or annual Items of vegetables,that have grown in foils unimpregnated withcommon fait, after being fufficiently dried arefet fire to, the watery, the refinous, the oily, theacid and carbonaceous portions are volatilizedand diffipated in a ftate of more or lefs com-pleat decompofition, and there remains behinda reddilh or whitiffi powder, called ajh or afhes ;confifting chiefly of the earthy and metallic in-gredients of the vegetables, together with a va-riable proportion of fub-carbonat of potalh. Bylixiviation with hot or cold water the alkalinepart is diffolved out, and this folution whenboiled down to drynefs leaves behind a darkbrown faline mafs, confifting of the carbonatedpotalh, coloured by a fmall portion of vegetableinflammable matter; and in this ftate it is knownin the Englifh market by the name of potajh.Calcination at a moderate red heat compleatlyburns off the colouring particles, and the fait be-comes of a fpungy texture, and beautiful bluilhwhite tinge, and is then called pearlafi. Suchis in general the procefs by which the vegetablefixed, alkali is feparated from the fubftances withwhich it is combined by nature, and preparedfor ufe. We fhall now proceed to defcribemore at large the different methods of extradit-ing this fait, together with the precautions thatare neceffary to fecure the greateft fuccefs.

The fimpleft and rudeft preparation of potalhis called cfh-balls in England, and weed-ajh inIreland . It cannot be faid properly fpeaking tobe an article of commerce, although a confider-able quantity is annually made by the peafantryof both countries, and difpofed of among theneighbouring farmers and bleachers. The ve-getable from which this impure alkali is pro-duced is the common fern or brakes (Pterisaquilina Lin.) Many rough and heathy dif-tridls are entirely covered with this plant, which

b Refearchcs, p. 75.