^Oj Proptrtions of CorhvH m Mineral Coal. 



than in Lavoifier's ftatement, and confequcntly much nearer than in mine : for, in his Eflay 

 on Plumbago, he tells us that five parti nitre are fufficient to confume one of charcoal, and 

 conft-quently it fliouIJ fcem that one part charcoal fliould decompofe no more than five of 

 nitre. The confcqucncc however is not juft, for undoubtedly five parts nitre would con- 

 fume one, of cliarcoal, but it docs not thence follow that they would not confume ftill 

 more. On the other hand, he found that ten parts nitre were ncceffary for the confumption 

 of one part of plumbago ; whence it follows, that one part of plumbago decompofes ten of 

 nitre, o:herwife nine parts nitre would fuiilce to confume it, and the tenth would have been 

 unneceflary, as it acls only as it is decompofed. Now this proportion approaches very 

 nearly to my refults -, namely, one of charcoal to 9,6 of nitre. 



Hence, and fmcc Kilkenny coal in the preceding experiments (hewed no fign of its con- 

 taining any thing bituminous, 1 take Ft for granted that it confiils almoft entirely of pure 

 carbon ; and fince 50 grains of it alkalize 480 grains of pure ignited nitre, that in all the 

 fubfequent experiments on other fpecies of coals or bitumens free from fulphur and iron, 

 the decompofition of this ftandard quaitfity of nitre will irtdieate, in the quantity of coal- 

 necelTary for that decompofition, the prefence of 50 parts of mere carbon. 



Before I proceed to the recital of other experiments, I muft mention another circumftance 

 that occurs in making tliem, which is, that, after the inflammation ceafes, a hifhng noife is 

 perceived for a long time, and is increafed on adding frefli quantities of coal, even when 

 the nitre is feemingly decompofed. This fcemed to me to arife from the decompofition of 

 the nitrous air, or mephitized nitrous acid, of which a portion is always retained by the 

 alkali ; and confequcntly I paid no attention to it, but always ceafed adding coal when the. 

 inflammation totally ceafed. 



Maltha: 

 ITS colour is dark-brown, or black. 



Luftre o. Tranfparency 0. Fraflure uneven, tough. Specific gravity 2,070. 

 It feels fomewhat greafy, yields to compreffion, has a heavy fmell, acquires a pollfli when 

 fcraped, does not adhere to the tongue, or flain the fingers; its flame high and bright, 

 leaving no coal, but only a little allies. 1 



Having but a fmall quantity of this fubftance, I on this occafion ufed only 240 grains of. 

 nitre : when it was heated to rednefs, I threw on it one grain of TCgetable pitch; it im- 

 mediately inflamed, but floated quietly on the furface of the nitre, and decrepitated Uke 

 common fait from the nioifture it contained : the flame was partly white from the action- of 

 the air fpontancoufly emitted by the nitre, and partly yellowifli from the a£lion of the am- 

 bient atmofpheric air, but fteady, and unattended with thofe turbulent gulhes that attend 

 the decompofition of nitre by carbonaceous fubllances. 



I then gradujJly pro]e£led on it 55 grains of maltha, which was all I had : this burned 

 juft as the pitch, but attended with a blacker fmoke ; yet the nitre was fo far from being 

 alkalized, that, to produce this effeft, I was obliged to throw on it 29 grains of cannel coal. 

 Now 33,5 grains of cannel coal, if it alone had been ufed, would fuflice to alkalize 40 

 crains of nitre : it will prefently be feen, therefore, the 55 grains of maltha and the one 

 grain of pitch contained no more carbon than 33,5 — 29 = 4,5 grains. Therefore 100 

 grains of' maltha contain no more than 8 grains of carbon. And as thefc 8 grains of car- 

 bon provoked no turbulent eruption of air from the nitre, it is plain they did not contribute 



