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ammonia. The fponge after this procefs be-comes more or lefs tranfparent, and confiderablyfoftened, and is then compleatly foluble in am-monia into a deep orange-coloured liquor.When digefted wifh boiling diftilled water,fponge gives out a portion of gelatin, which isprecipitated by infufion of oak-bark. Thefponge by lofing its gelatin, becomes much lefsflexible than before, and is eafily tom whenmoift, or crumbles between the fingers whendry. When fponge either in its natural ftate,or efpecially when its gelatin has been extractedby long boiling with water, is boiled with caufticpotafh, it compleatly diffolves therein and formsan animal foap.
Sponge, when heated in a clofe vefTel, givesout an ammoniacal fetid fmoke, and is reducedto a black charcoal, which, after incineration,leaves a fmall quantity of common fait and fomecarbonat of lime.
Charred or burnt fponge is ufed in medicine.
The chief conftituent parts of fponge there-fore are, animal gelatin, and that condenfedalbumen which Mr. Hatchett has found to bethe principal part of all foft membranous organs,of cartilage, &c. The former is diffolved, thoughwith fome difficulty, in boiling water, but doesmot yield to cold water \ the albumen is info-Iuble in water at any temperature, but yields tocauftic alkali.
STAHL’s SULPHUREOUS SALT. SeeSulphite of Potajb.
STANGENSPATH. See Heavy Spar.STALACTITE ? 0 T
STARCH. Amidon , Fr. Starkmehl, Germ.
Under the article Fecula , the chemical pro-perties of the ftarch, or fecula of all vegetables,have been defcribed ; we have therefore only inthis place to mention fhortly the mode of manu-facturing the common ftarch which is made,for fale, almoft exclusively from wheat. Thisgrain confifts of gluten, fecula, a colouring ex-tractive matter, and phofphat of lime, and it isthe objeCt of the ftarch-maker, to feparate thefecula alone from all the other ingredients.This might be done, one would think, Amplyby grinding the wheat into very fine flour, mix-tng the flour with water into a ftiff pafte withmuch beating, and then expofing this pafte withuninterrupted agitation to a gentle current ofP ur ® • wa * er » ' v hich would run off milky withthe ftarch as long as any of it remained in the
pafte, and the gluten alone would be left be-hind. This milky water would depofit theftarch by remaining at reft for a time.
A fimilar method is followed in the final!way in making potatoe ftarch, as mentionedunder the article fecula, only with lefs labour,as this contains no gluten.
Wheat ftarch is not made however exaCtly inthis Ample way, but the grain after being coarlelyground, is fuffered to ferment or mould withwater for many days, by which its texture is en-tirely broken down, and the ftarch which isfcarcely alterable in the procefs, is probablymore effectually feparated from all the otheringredients, and obtained Aner and whiter. TheaCfual method is (in a few words) the follow-ing: 1 The wheat is Arft coarfely bruifed, andplaced in large wooden vats or refervoirs, water-tight, and intimately mixed with water. Herea fermentation begins after a time, which is amixture of the vinous and acetous, and is at-tended with a ftrong, unpleafant, four, mouldyfmell. The wheat remains in the vat for abouta fortnight, till the fermentation ceafes, whichis known by its fettling at the bottom of the vat.The contents are then emptied fucceffively intoa fmall tub, and mixed with frefh water, till allthe pulpy part is thin enough to pafs through ahair Aeve, whieh feparates the bran from it.What has gone through contains the ftarch fuf-pended in a very four water, and confiderablyfoul. This is put into tubs or frames, and al-lowed to remain for two days undifturbed, duringwhich the impure ftarch fettles to the bottom.The water is then drawn off, the frames turnedon their ftdes, and the dirty difcoloured part ofthe ftarch (which is the laft that fubftdes andtherefore is at the top) is fcraped off, and the?remaining ftarch is well walhed and brufhed,till it is nearly free from this muddy fediment,which is called Jlimes , and is treated feparatelyto obtain its ftarch. The ftarch is ftirred withfrefh water, and fuffered to fettle, and againcleanfedj till all its impurities are removed, andis then mixed with water enough to make itliquid, and paffed through a ftne lawn Aeve. Itis then At to receive its colour, which conAftsof fmalt mixed with water and a fmall quantityof alum, and is thoroughly incorporated with theftarch. After again fettling, the ftarch is takenout and put into oblong boxes, about Ax feetlong and one broad, with holes at the bottom,and lined with linen cloth, where the moiftureof the ftarch drains off till it becomes folidenough to be cut into fquare lumps. Thefe ar e
• Original Communication.