Prtptriioiis of Carbon in Mintral Coal- 



^^U 



Kilkenn-j Coal. 



fTS colour IS black, an3, when freOi broten, frequently violet. 



Luftre 4, Metallic. Tranfparencyo **. 



Fra£ture foliated, the courfe of the lamellx variouDy and confufedly direfled. Frag- 

 aflents rather (harp, and often difcovering between the diftiniSt concretions whitifli illinitions. 



Hardnefs 7. Specific gravity 1,526. 



Does not burn until vi'holly Ignited, and then (lowly confumes without caking or emitting 

 flame or fmoke. 266 grains of it expofed toa heat of 27° Wedgwood in a crucible for five 

 hours, did not lofe their luftre until almofl: -r'a of them had difappeared, and at laft left red- 

 difliafhes amounting to 7,13 grains, nearly 2,7 per cent. Projeding this coal in fine powder 

 on 480 grains of pure ignited nitre, 1 found the fait required 65 grains of the coal to alka- 

 lize it, but only 50 grains when in coarfc powder ; and in a tliird experiment, when the cru- 

 cible was farther from the flue of the furface, only 49 grains; fo that I look upon 50 grains 

 as being in round numbers neareft to the truth. That is, in the proportion of one part of 

 Kilkenny coal to 9,6 of nitre: or, top parts of nitre require for their decompofition 10,416 

 ef Kilkenny coal. 



This proportion of coal is much fmaller than that of charcoal in Mr. Lavoifier's experi- 

 ment, which we have feen to be as 1 to 7,57, or as 13,21 to 100, which I attribute to the 

 advantageous mode in which his experiment was inftituted, as already explained ; whereat 

 in mine, and the ufual way, the decompofition of nitre is promoted by the external heat 

 applied, as well as by the coal, and confequently lefs of the coal is employed. 



From the experiments of Scheele one might be led to infer, that the proportions of char- 

 coal and nitre necefiary to the alkalization of this latter, approach ftill nearer to each other 



* The figures made ufe of by this author to denote degrees of luftre, tranfparency, hardnefs, and (harpncfs of 

 fitjments, arc explained in the following Table, which I have conftruftcd from his fection upon the diftinftive 

 chara£ter9 of minerals. 



On account of the higher range of niimljcrs, degrees of hardnefs could not conveniently be included iR the 

 ibove- Table. No. 3, denotes the hardnefs of chalk ; 4, a lUperior hardnefs, but yet what yields to the nailj, 

 > , tlut v/hich will not yield to the nail, but eafily and without grittinefi to the knife; 6, that which yields 

 riioic difRcultly tp the knife ; 7, thai v hjch fearci-ly yields to the knife ; S, that which cannot be fci;aped by X 

 V.nlfe.^ut does not give fire with fteel ; 9, that which gives a few feeble fparks with (leels, a't bnult'i 10, that 

 'vWcli'gi-eipler.tirul'rvely fpark'f as flint. K. - -'•''■'■'•' C.i' '-•' 1 ;. , 



-! R 2 thaN 



