CAR

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apparatus made ufe of on this occafion was atube of gold clofed at one end, and terminatingat the other in a curved glafs tube, fo as to an-fwer the purpofe of a retort. By way of pre-vious trial fame purified nitre was heated in thetube till it became alkaline, and being then dif-folved out by water the folution was found tobe abfolutely free from carbonic acid, as it didnot affeft the tranfparency of lime-water. Hav-ing thus fatisfied himfelf with regard to the per-fection of his apparatus, Mr. T. filled the tubewith a quarter of an ounce of nitre and twograins and a half of fmall diamonds: the goldtube was then heated to a full red, and kept atthis temperature for an hour and a half. Thegas difengaged during the procefs was afcer-tained by the teft of lime-water to contain onlyan extremely minute portion of carbonic acid.The alkaline refidue of the nitre was then dif-folved out of the tube by water, and not thelead; trace was found of the diamonds. Thefolution being mixed with muriat of lime a co-pious precipitate fell down, which being care-fully colleaed was placed in a fmall glafs globewith a tube annexed: mercury was then pouredin to fill it, and the apparatus was inverted in abafon of the fame fluid. Some muriatic acidwas then introduced by which the calcareousprecipitate was difiolved, and the carbonic acidthat it contained was at the fame time difen-aged and collected in the annexed tube. Theulk of carbonic acid was fomething more thanto.i ounces of water, at 55° Fah. 29.8 Barom.A fecond experiment was made in a fimilarmanner with one grain and a half of diamonds,and the carbonic acid obtained occupied thefpace of 6.18 ounces of water, according towhich proportion the bulk of the carbonic acidfrom 2.5 grs. of diamond would have been— 10.3 ounces. The carbonic acid thus dif-engaged was again combined with lime, and byheating it in a clofe tube with phofphorus thecarbonic acid was decompofed, and its carbon-aceous bafe which at the commencement of theexperiment was diamond, affirmed now theblack colour and other characters of charcoal.The identity of charcoal and diamond is (tillfurther confirmed by comparing the quantity ofcarbonic acid produced from the combultion ofeach. Lavoifier, from feveral experiments whichhave been acquiefced in by all chemifts as fuf-ficiently accurate, has {hewn that 1 part of pure. , rc T al .requires 2.5 parts of oxygen for itsacidification ; or that ico parts of carbonic acidContain 28 charcoal and 72 oxygen. How af-

firming the medium of Mr. Tennant’s experi-ments as approaching very nearly to the truth,it follows that 2.5 grs. of diamond yield 10.2ounce meafures of carbonic acid at 55 0 tempe-rature, and 29.8 barometrical preffirre. But Iounce meafure is = 1.89 cub. inch, and 1 cub.inch of carbonic acid weighs 0.467 grain: there-fore 2.5 grs. diamond yield 9.03 grs. of car-bonic acid; and the correfpondence of this withthe proportion of charcoal deduced from theexperiments of Lavoifier is manifeft from thefollowing equation,

: roocarb. acid : 28 char.:: 9.03 carh.acid : 2.521 diamondSince the publication of Mr. Tennant’s paperthe fubje£t has been refumed by Morveau at thePolytechnic fchool at Paris , with no fmall paradeand pretenfions to accuracy; and as he hasdrawn from his experiments and calculationsnot only very different refults from Mr. Ten-nant, but has made them the bafis of a newhypothefis, it is requilite to enter into their ex-amination with fome minutenefs.

b A globular receiver of glafs was filled with11470 cubic centimetres (450 cub. inch.) of oxy-ygen gas, and a diamond of the weight of 200millegrammes (3.08 grs.)was placed within it: bythe a£Hon of a powerful lens the diamond wasconfumed and carbonic acid produced. A quan-tity of barytic water was then introduced, anda white precipitate of carbonated barytes wasthrown down, weighing when dried at 212°. 192centigrammes : now, as carbonated barytes ac-cording to Pelletier contains 22 percent, of car-bonic acid, thefe 192 centigrammes reprefent 42centigrammes (6.48 grs.) carbonic acid. The gasremaining in the receiver amounted to 11242centimetres, and ftill contained carbonic acid,for on mixture with ammonia it experienced adiminution of i'omewhat more than 4 per cent,which gives 448 centimetres (8.21 grs.) moreof carbonic acid. Hence it appears, that al-though 28 parts of charcoal and 72 of oxygencompofe 100 parts of carbonic acid, yet thefame quantity of carbonic acid requires only17.88 diamond and 82.12 oxygen. M.Morveautherefore infers that diamond is pure carbon,and charcoal an oxyd of carbon, being compofedof 63.85 carbon and 36.15 oxygen: this con-clufion he confiders as llrengthened by the ex-periments on plumbago by Scheele , who foundthat twice as much charcoal was requifite to al-kalize a given quantity of nitre, as of plumbago,and that 80 centigrammes of the fame whendiftilled with 20 parts of nitre yielded 357 cubiccentimetres of carbonic acid.

* An. de Chim. jpud. p 85.