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refinous fediment falls down. The fupernatantliquor evaporated nearly to drynefs yields afaponaceous extract, which retains much of theflavour of the myrrh. Alcohol digefted withmyrrh forms a very ftrong-frnelling, intenfelybitter tinddure, of a very fine golden yellowcolour, which is made turbid by the additionof water.

Guaiacum. This fubftance has ufually beenreckoned among the perfedd refins, but lateexperiments (though they are not compleat,)fhew that it has fome very peculiar properties,-fo that it cannot be clafled properly either withthe gums or refins.

This gum is procured from the Guaiacumwood, or Lignum vita, which is a very hard,ponderous wood, obvioufly abounding withrefin, and as it were foaked in it, fo that ithas a peculiar greafy feel, and a very ftrongand peculiar fmell when rubbed.

Gum guaiacum is brought over in irregularmafles, eafily friable, of a dulky green colour.It is in fome degree tranfparent, and it breakswith a vitreous fracture. When pulverized, itis of a grey colour, but becomes green onexpofure to air. 1 It melts when heated, andgives a very pungent aromatic odour. Thefmell is fragrant; it gives fcarcely any tafte inthe mouth, but when fwallowed, it excites aftrong burning fenfation in the throat Mr.Hatchett has obferved that guaiacum, thoughapparently a pure refin, differs from all the purerefins in giving much oxalic acid by the nitric,and in yielding fcarcely any artificial tanninwith the nitric acid. Mr. Brande has fincegiven an interefting analyfis of this fubftance. b

When pulverized guaiacum is digefted in amoderate heat in diftilled water, an opakefolution is formed, which becomes clear onpaffing the filter. This liquor is of a greenifhbrown colour, and a fweetifh tafte. Themuriats of alumine and tin, and nitrat of filver,all caufe a brown precipitate, and when theliquor is evaporated an extraB is left. O-nehundred grains of guaiacum yield about 9 grs.of this extradd, which alfo contains fome fait oflime, as'{hewn by the oxalic acid.

Alcohol diffolves guaiacum with eafe, leavingabout 5 per cent, of extraneous matter undif-folved. This folution is of a deep browncolour, and is decompofed by water, whichfeparates the refin and leaves the liquor of amilky hue. If muriatic acid is added to thealcoholic folution, the refin at firft feparates,

which an excefs of the acid rediflolves. Theaddition of nitrous ether to the tinddure andfubfequer.t dilution with water, caufes the refinto precipitate, which foon acquires a fine bluecolour, 0 and this change of colour appearscharadderiftic of the refin of guaiacum, and hasbeen employed as a means of detedling anyadulteration. Liquid oxymuriatic acid addedto the tincture alfo precipitates the refin imme-diately of the fame blue colour. d Acetic acidcaufes no precipitate, the refin being readilyfoluble in this acid. Nitric acid diluted withone fourth of its weight of water, turns thetindture green, and gives a green precipitateafter {landing fome hours, but the colour foonchanges to blue, and afterwards to brown.

Alkalies do not caufe any precipitation in thetindture.

The guaiacum in fubftance {hews the follow-ing eftedts with the different reagents.

Sulphuric ether diffolves it though lefs abun-dantly than alcohol.

Sulphuric acid adds on it nearly as on theother refins, and finally chars it, leaving 58grs. of coal from 100 of the refin. 0

Nitric acid adds upon it in a peculiar manner:100 grs. of guaiacum were added to 2 oz. ofthis acid of 1.39 fp. gr. f the refin at firft be-came of a dark green colour, a violent effervef-cence was excited with the produddion of muchnitrous gas, and the whole was diflolved with-out the afliftance of heat. This folution, leftat reft for fome hours, depofited cryftals ofoxalic acid. In this laft circumftance, and inthe ready folubility in cold nitric acid, guaiacumdiffers effentially from the other refills.

Dilute nitric acid added fomewhat differently,and diflolved only part of the guaiacum, andthe remainder was converted into a chocolatebrown fubftance, apparently the fame as thatproduced by adding the fame acid to thetinddure after it has palled through the changesof green and blue. This brown fubftance nowmore compleatly relembles the true refins,being equally foluble in alcohol and ether, andinfoluble in water. If this is further decom-pofed by nitric acid, in the way mentionedby Mr. Hatchett, it is converted into artificialtannin.

The alkalies, pure and carbonated, diflolveguaiacum with eafe.

RETORT.

An article of chemical apparatus, for an at-count of which fee the Appendix .

a Murray, Appar. Med.Med' vol * Brands*

Pliil. Tranf. for 1806.

6 Hatchett, { Brande.

' Monch, in CrcIl’J Journal, or Murray, Appar.