jji Conibiijlkn cf tht Ditimond iy the Soltir Focus and by Nitre. 



property, was induced to conjc^ure that the diamond itfelf was of an inflammable nature. 

 The inflammable fubftanccs which he employed were camphor, oil of turpentine, oil of 

 olives, and amber ; thefe he called " fat, fulphureous, unftuous bodies ;" and ufing the fame 

 exprefiion refpcdting the diamond, he fays, " it is probably an unftuous body coagulated." 

 This remarkable conjeflurc of Sir Ifaac Newton has been fince confirmed by repeated experi- 

 ments. It was found, that though the diamond was capable of refilting the efFctts of a violent 

 heat when the air was carefully excluded, yet, that on being expdfed to the aiStion of heat 

 and air it might be entirely confumed. But as the fole obje£t of thefe experiments was 

 to afcertajn the inflammable nature of the diamond, no attentitjn was paid to the produfts 

 afforded by its combuftion ; and it ftill therefore remained to be determined, whetlier the 

 diamond wns a dillin<n fubftance, or one of the known inflammable bodies. Nor was any 

 attempt made to decide this queflion till M. Lavoifier, in 1772, undertook a feries of ex- 

 periments for this purpofe. He cxpofcd the diamond to the heat produced by a large lens, 

 and was thus enabled to burn it in clofe glafs veflels. He obferved that the air in which 

 the inflammation had taken place had become partly foluble in water, and precipitated 

 from lime-water a white powder, which appeared to be chalk, being foluble in acids with 

 effervefcence. As M. Lavoifier feems to have had little doubt that this precipitation was 

 occafioned by the produ<Slion of fixed air, fimilar to that which is afforded by calcareous 

 fubllances, he might, as we know at prefcnt, have inferred that the diamond contained 

 charcoal ; but the relation between that fubftance and fixed air was then too imperfeftly 

 underftood to juftify this conclufion. Though he obferved the refemblance of charcoal 

 to the diamond, yet he thought that nothing more could be reafonably deduced from their 

 analogy, than that each of thofe fubftances belonged to the clafs of inflammable bodies. 



As the nature of the diamond is fo extremely fingular, it feemed deferving of further 

 examination ; and it will appear from the following experiments that it confifts entirely of 

 charcoal, differing from the ufual ftate of that fubftance only by its cryftallized form. From, 

 the extreme hardnefs of the diamond, a ftronger degree of heat is required to inflame it, 

 when expofed merely to air, than can eafily be applied in clofe veffcis, except by means of 

 a ftrong burning hens; but with nitre its combination may be effeiiled in a moderate heat. 

 To expofe it to the aclion of heated nitre free from extraneous matters, I procured a tube 

 of gold, which, by 'having one end clofej, might ferve the purpofe of a retort.; a glafs tube 

 being adapted to the open end for collefting the air produced. To be certain that the gold 

 Ycflel was perfeftly clofed, and that it did not contain any' unperceived impurities which 

 could occafion the produdlion of fixed air, fome nitre was heated in it till it had become 

 alkaline, and afterwards diffolved out by water;' but the folution was perfectly free from 

 Axed air, as it did not affedl the tranfparcncy of lime-water. When the diamond was de- 

 ftroyed in the gold veffel by nitre, the fubftance whi'rh remained precipitated lime from 

 lime-water, and with acids afforded nitrous and fixed air; and it appeared folely toconfift of 

 nitre partly decompofed, and of aerated alkali. ' 



In order to eftimate the quantity of fixed air which might be obtained from a givea 

 weight of diamonds, two grains and a half of fmall diamonds were weighed with great ac- 

 curacy, and, being put into the tube with a quar'ter of an ounce of nitre, were kept in a 

 lUong red heat for about an hour and a half. The heat being gradu.illy increafcd, the 

 nitre was in fome degree rendered alkaline before the diamond began to be inflamed ; by 

 which means almoft all the fixed air was retained by the alkali of the nitre. The air which 



cam? 



