COR

COR ( 552 )

.not been previoufly boiled with water, but other-wife of an afh-grey , a

Cork is corroded, and almoft entirely diffolvedby nitrous acid, and in 1787 Brugnatelli repeat-ing this experiment, thought that a peculiaracid was thus produced. The inveftigation wasafterwards taken up by B. La Grange with thefollowing refult. b He took finely rafped cork,and added to it in a retort fix times its weightof moderately ftrong nitrous acid. By digeftionat a moderate temperature nitrous gas is givenout, the cork fwells and becomes yellow, andfinally is almoft entirely diffolved. When thered vapours ceafe, the liquor is to be transferredinto a glafs capfule, and is to be gently evapo-rated till it becomes thick, and a pungent vapourbegins to be difengaged. A fubftance is thusprocured of the confidence of thick honey, of alemon-yellow colour, and a lively, penetrating,aromatic odour. In order to feparate the acidgenerated in this procefs from the other matterswith which it is mixed, the whole is to be dif-folved in twice its weight of hot diftilled water,and paffed quickly through a filter, by which afmall quantity of an inflammable fubftance ana-logous to wax will be feparated. The clearliquor is of a light amber colour with an odourapproaching to that of prufiic acid. By refri-geration it becomes turbid, and depofits a pul-verulent fediment which is the acid of cork, orfuberic acid. The acid yet remaining in themother liquor may likewife be obtained byrepeated evaporation and cooling. The fubericacid thus prepared is of a yellowilh-browncolour, but may be whitened by being boiledwith frefh burnt charcoal. When pure it is ina folid form, but not cryftallizable; it is acidulousand bitter to the tafte, is volatilizable by a mode-rate heat, decompofes all the metallic and manyof the earthy falts, and combines with the alka-lies into cryftallizable falts. Hence it is con-fidered by La Grange as a peculiar acid, andFourcroy has ranked cork, under the name Suber,as one of the vegetable principles.

The two chemifts however, above-mentioned,appear to have been led into an error from nothaving examined the compofition of cork pre-vious to treating it with nitric acid, on whichaccount the following facts c may not be unac-ceptable to the reader.

If cork previoufly reduced by filing to ex-tremely fine powder, is digefted with alcohol, abrownifh-yellow tinfture is produced, pofleflingthe faintly aromatic odour of cork, and caufing

8 Neumann, ii. p. 228 . b Manuel de (

* Crcville, Bournon, Chenevu, and Tennant, in Phil.

a flight ochery precipitate in red fulphat of iron:this alcoholic folution being evaporated to dry-nefs by a very gentle heat, leaves behind abrittle brownifti fediment, of a fomewhat aftrin-gent tafte, and confiderably inflammable. Bydigeftion with water a portion of it is diffolved,confifting principally oi gallic acid and tannin;for it forms a black precipitate with red fulphatof iron, and throws down a curdy infolubleprecipitate from a folution of ifinglafs. Theportion infoluble in water appears to be chieflyrefinous, and this, no doubt, it is which marksthe peculiar characters of the gallic acid in thealcoholic folution. After alcohol has extractedfrom cork all that it is capable of taking up, therefidue, when digefted in a weak folution ofcauftic potafh, acquires a deep reddifh-browncolour, which it communicates to the men-ftruum. Muriatic acid added to faturationnearly deftroys this colour without occafioningany fenfible turbidnefs, nor does the neutralizedfolution produce any change in red fulphat ofiron, fo that it is probable that the alkali dif-folves little or nothing but a fmall quantity ofcarbon. Hence it appears likely that the fubericacid of La Grange is only gallic acid convertedby nitrous acid into oxalic acid, and combinedwith a little refinous extradf ; and that the fuberof Fourcroy confifts of vegetable fibre in a veryloofe ftate, mixed with refinous and extractivematter, and a little tannin and gallic acid.

CORK, Mountain. See Asbest .CORROSIVE SUBLIMATE. See Mer-cury, Muriat of.

CORUNDUM . a Of this mineral there arethe three following fub-fpecies.

1. Telefia. PerfeB Corundum , Bournon.Tele/te, Hauy. Saphir, Werner. Sapphire , Ori-ental Ruby, &c. of the jewellers.

Telefia exhibits a great variety of colours.It is pearl-grey, bluifh-white, lavender blue, Ikyblue, azure or indigo-blue, and then is the fap-phire of the jewellers ; or it is peach, crimfon,cochineal, and very rarely carmine red, and isthen called oriental ruby; hence it paffes intoviolet coloured, forming the oriental amethyft ;when yellow or reddifh yellow it is denominatedoriental topaz; when yellowifh-green, orientalchryfolite; and when of a deep fomewhatbrownifti green it is named oriental emerald.The colours are for the moil part uniformlydiftributed, but fometimes two or more occurin the fame fpecimen.

It occurs in fmall rounded pieces or cryf-

am, ii. p 414- c Orig* Experiments.

'ranf. for 1798 and x8q 2. Janaefon, Hauy, Brochant.