SUL
SWI
( 396 ) •
adding together the two fulphites. It occursin the ftate of fmall tranfparent indeterminatecryftals; it is lefs foluble in water than eitherof the two fulphites feparately, of which it iscompofed. By expofure to air it changes intothe triple fulphat of ammonia and magnefia.When heated it gives out firft fulphurous acid,then acidulous fuiphite of ammonia fublimes,and pure magnefia remains behind. The pro-portion of its conftituent parts has not beenafcertained. It is decorrlpofable by barytes,ftt'ontian, lime, and the fixed alkalies. It isnot made any ufe of.
Sulphite of Alumine.
This fait is formed from pure alumine, ac-cording to the procefs already mentioned. Itis in the ftate of a white foft powder; to thetafte it is fweetifh, and then fulphureous. It isinfoluble in water, but is taken up by an excefsof acid. It is not cryftallizable. By expofureto the air it is gradually converted into fulphat.When heated, fulphurous acid is driven off andthe earth remains behind, together with a littlefulphat. It is compofed, according to Dr.Thomfon, of
32 Sulphurous acid44 Alumine24 Water
100
It is not applied to any ufe.
The fumach is a fhrub which grows natu-rally in Spain, Portugal, Syria , and many partsof the Levant, and is largely employed in dye-ing. 1 Every part of the tree appears impreg-nated with aftringent matter: the entire twigsand branches are the parts employed, whichare dried, and ground in a mill into a coarfebrown or yellowifh-green powder, which is theftate in which.it is imported.
Sumach readily yields a yellowifh green in-fufion with warm water, which foon turnsbrown on expofure to air. This infufion givesa fmall quantity of yellow lake with alum, andwith the folutions of iron it forms an abundantblack or dark brown precipitate, fhewing theprefence of gallic acid. It is largely ufed indyeing; by itfelf it gives a yellow-buff orfawn colour tending to green, which however isfugitive unlefs fixed by a mordant. If a fait ofiron enters into the mordant, the black of the
gallat of iron then produced mixes with the na-tural colour of the fumach, and a valt varietyof ufeful grey, drab, and flate colours arebrought out. Sumach, like the gall-nut, alfocontains a very large quantity of Tati , andhence will give a copious precipitate with infu-fion of glue or any other animal jelly; f 0 thatit has an additional ufe in the preparation ofleather, the finer kinds of which (as mentionedunder that article) are tanned by fumach.
A good deal of fulphat of lime is found inthe infufion of fumach, by the barytic and ox-alic tefts. The infufion of this plant differsfrom that of the other aftringent vegetables ingiving a precipitate with the cauftic alkalies,which is probably owing to the fulphat of limewhich it contains. (See the article Tannin.)Mr. Davy obtained 105 grs. of matter folublein water from 480 grs. of Sicilian fumach, ofwhich he eftimates 78 grs. to be tannin,
SWINESTONE. Stinkjlein , Wern. Pierrepuatite , Broch.
Its colour is dark fmoke-grey palling intogreyifli black, yellowifh grey or blackilh brown.It occurs in mafs, and fometimes diffeminated.Its internal luftre varies from dull to glimmer-ing. Its fracture is fine grained fplintery, orfine grained earthy; fometimes it is imperfe&Iylamellar or flaty; the black variety is more orlefs conchoidal. Its fragments are either inde-terminately angular, or llaty. It fometimescontains very fma 11-grained diftinct concreti-ons. It is opake, fometimes a little tranflucenton the edges. It gives a greyilh-white ftreak,may be eafily fcratched with a knife; is brittle,and eafily frangible; when rubbed it gives outa ftrong fetid urinous odour (whence its name.)
It effervefces ftrongly with acids, and the gasthus liberated is carbonic acid mixed with a littlefulphuretted hydrogen. By calcination it be-comes white, and is converted into quicklime.
It occurs in beds alternating or intermixedwith ftratified gypfum, or ftratified limeftone.It is found in England, Germany, France , andmoft other countries. The harder and morecompact varieties being capable of a good po-lifh are often employed in ornamental architec-ture for marble. It is alfo ufed as a materialfor building, and when burnt affords excellentquicklime. Its peculiar odour has been attri-buted by fome to a mixture of bitumen, andhence it has been improperly confounded withbituminous limeftone.
* Berthoilet Art de la Tdnture,