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nefia be added to the carbonated ammonia, thefub-carbonat of ^magnefia is equally produced.In either cafe all'o a part of the ammonia uniteswith the magnefia, according to Fourcroy, form-ing a triple fait, the ammoniaco-magnefati carbonat.The fame triple fait alfo is formed by addingthe compound muriat of ammonia with mag-nefia to carbonat of potafh or foda. The pro-perties of this triple fait are not well eftablifhcd,but its fuppofed formation in the above circum-ftances correfponds fufficiently well with theknown tendency of ammonia to fuch triple com-binations.
Magnefia is only ufed in medicine.
Carbonat of Alumine , Glycine , Zircon , See.For the remaining earthy carbonats fee the re-fpe&ive earths.
Carbonats Metallic. See the refpectivemetals.
CARBUNCLE. See Spinell.
CARMINE is a beautiful red precipitate ofthe colouring matter of Cochineal (which fee).
CARTHAMUS. See Safflower.
CARTILAGE . This organ which appearsto hold fomewhat of an intermediate ftate be-tween ligament and bone appears, according toMr. Hatchett’s refearches to confift chiefly ofcondenfed albumen.
Some parts, fuch as the joinings of the ribs,remain cartilaginous through life; in others thecartilage is the firft rudiment of bone, thatwhich determines its fhape and pofition, and itbecomes folid bone by the gradual depofition ofofleous matter. Thefe may be again feparatedin a great meafure by acids which diffolve thebone and leave the cartilage. See Bone andAlbumen.
CASSIUS, Powder of, is a beautiful precipi-tate formed by immerfing tin in a folution ofgold, or by mixing the nitro-muriats of eachmetal. It is ufed to give the fineft ruby co-lour to Glass. See alfo Gold.
CATECHU or TERRA JAPONICA.
This fubflance, concerning the origin of whichthere was formerly much doubt, is an infpiflatedextraCt prepared in feveral parts of India , froma fpecies of Mimofa, by decoction of the woodand evaporation to drynefs. The tree is calledin the Bahar province Coira, and the extraft hasthe feveral names of catechu, catch or cachou.
It is thus prepared, according to Mr. Kerr,an eye-witnefs. a After felling the trees themanufacturer cuts off all the exterior white part.of the wood, which is rejected. The inner
wood which is red, and from which alone theextract is prepared, is cut into chips and boiledwith water till half is evaporated. This ftrongdecoCtion is then poured off without {training,into a {hallow earthen pot and evaporated toone-third by fuel, after which the thoroughdrying is compleated by the heat of the fun,the thickened extract being fpread thin on amat and expofed to the air. In this Amplemethod is the catechu prepared, but it is oftenmixed accidentally or fraudulently with fandor other earthy impurities, fometimes to theamount of one-eighth of the whole, as appearson analyfis. b
There are two varieties of catechu broughtto this country, from Bengal and from Bombay,but differing very flightly in chemical qualities.
Catechu is of a red brown colour, uniform intexture, brittle and friable, and without fmeli.Its fpecific gravity from 1.28 to 1.39. Thetafte is ftrongly aftringent, and at firft fomewhatbitter, but afterwards leaves a permanent andagreeable fweetnefs. It diffolves flowly and to-tally in the mouth, the earthy impurities ex-cepted.
Catechu is Important in a chemical point ofview, from the unufually large quantity of tan-nin which it has lately been found to contain,and which therefore promifes to render it ufefulin the preparation of leather. See Tannin.
By the analyfis of Mr. Davy, c at the fuggef-tion of Sir J. Banks, it appears that there is verylittle difference between the two fpecies, andtherefore the defeription of one will ferve forboth.
Catechu is almoft totally foluble in hot water.The folution is of a deep red-brown, and flightlyreddens litmus. By long decoCtion a folutionis made, which yields by evaporation as muchas of its weight of folid matter.
With chemical reagents nearly the fame ef-fects were produced as when the fame reagentsare added to infufion of Galls , and will bementioned under that article. In particular theprefence both of the gallic acid and of tanninwere fully afeertained, the former among othertefts by the black produced by fulphat of iron,and the latter by the copious precipitate withanimal gelly.
Befides tannin and gallic acid, catechu con-tains a peculiar extract, and alfo a fubftancerefembling mucilage. The latter is left nearlypure after the aftion of alcohol, which readilydiffolves all the reft. It fcarcely differs fromcommon gum mucilage. The extractive matter
•Medical Obfervations, Vol.j. ‘ Lewis’s Mat. Med. * Phil. Trani. for 180,3.