CAR

CAR

( 233 )

fore (reducing the whole to Englifh meafure)

: 60.9 grs. carbon, acid : 12.3 grs. plumbago : : 100 : 20.1

fo that a lefs proportion of plumbago is requiredfor the formation of carbonic acid than even ofdiamond, and this without taking into accountthe 5 per cent, of iron contained in plumbago.

If thefe objections to the experiments of M.Morveau are well founded, we mult return tothe deductions of Mr. Tennant, and confidercharcoal and diamond as very nearly the famefubllance chemically fpeaking, though differingfo materially in many other refpedts; and asbearing to each other the fame analogy as chalkto calcareous fpar, alumine to fapphire, filex torock-cryftal.

Diamond when placed in the focus of apowerful lens in contact with oxygen gas pre-sents the following phenomena. Itfirft becomesof a clear red, and foon after is apparently en-larged in bulk by being furrounded by a faintwhite light, indicating it to be in a date of corn-bullion : minute black fpots, having a leadenmetallic luftre occafionally form on its furface,efpecially when there is a flight remiffion of theheat; the diamond.gradually diminilhes, and atlength is entirely confumed without leavingthe fmalleft refidue. It Is fomewhat remark-able, that although in a date of actual ignitionand furrounded with oxygen gas, it neverlhelefsimmediately ceafes to burn as foon as the focusof the lens is withdrawn. The belt obferva-tions on the combuftion of this Angular fub-ftance by the heat of a furnace, are to be foundin a valuable paper by Sir George Mackenzie /A diamond being placed on a thin piece of bakedclay, was introduced into a muffle previouflyheated red hot: it foon acquired the fame red-nefs as the muffle, and in a few feconds morebecame viflble by a bright glow. Being thenremoved from the fire it was found to have ac-quired a flight milky appearance, and its luftrewas impaired, but no black fpecks were per-ceived on its furface. A diamond and. a piece-of plumbago were introduced together into amuffle; the latter was obferved to exhibit thefame luminous appearance as the former, only,it began at a lower temperature. The air beingexcluded for a few minutes by cloftng the mouthof the muffle, both the diamond and plumbago,loft their brightnefs ; but this foon returned onagain allowing.the air to circulate through themuffle, and. was . increafed in both by blowingon them with a pair of bellows. The tempe-rature required for the combuftion of diamond

’ Nicholfon’s Journ. 410. IV. p. 103. e An. Chim.

TOX.. I.

is lower than has been generally fuppofed ; SirG. Mackenzie found that at 13 0 Wedgewood,the diamond had acquired the dim milky appear-ance juft mentioned, and that the highelt heatnecefiary for its compleat combuftion did notexceed 15°

In order ftill further to afcertain the identityof diamond and charcoal, it was ingeniouflyfuggefted by the French chemifts to attempt toconvert iron into fteel by means of diamond in-ftead of charcoal. This was fuccefsfully per-formed by Clouet/ and afterwards repeatedwith fome variations by Sir G. Mackenzie , inorder to obviate certain objections that had beenraifed againft the accuracy of the experiment..

The above are all the chemical fadis hithertoknown concerning diamond or carbon in itspureft ftate: we fliall now proceed to treat ofcharcoal.

Charcoal.

The great confumption of charcoal is as fuel,and the mofl ufual material of which it is pre-pared is wood. The mofl: efteemed kinds ofwood for this purpofe are. oak, chefnut, elm,beech, and afh; the white woods and thofewhich abound in refln being commonly reject-ed. Large timber, befldes being too valuable tobe thus employed, furnifhes only a very inferiorflaky kind of charcoal, the beft being producedfrom coppice wood, the Items of which are fromhalf an inch to two inches in diameter. Piecesthree or four inches thick are not indeed rejected,but they require to be cloven in four previous tocharring, which is fome additional trouble, and -the produce of charcoal is fmaller in proportionthan of the entire pieces. The wood when firftcut down a is formed into large faggots, which-are dried in the open air for two or threemonths, and are then in a fit ftate to-be made-into charcoal. For this purpofe it is forted intobrufh wood, the fmaller items, and the largerones, the two latter of which are cut into trun-cheons from two to three feet in length. A-fquare or circular fpace about fifteen feet in-diameter is then marked out in a dry fhelteredfpot, and the turf is carefully removed from itsfurface, which is beaten till it becomes quitehard, dry, and folid: a thick flake fomewhathigher than the- intended pile is driven into the-centre of the area, and a thin ftratum of brufhwood is ftrewed evenly over the whole fpaceferving as a foundation for the reft. Abovethe brufh-wood is laid a ftratum of trunch-eons, taking care to place the thickeft near theicentre, and the thinneft at the edges: over thisxxxi. p. 3*8, ■ Arts et Metiers art. Charbor.nier,.

2 G