CAR
CAR
( 232 )
The above are the principal fa£b and infe-rences contained in the memoir of M. Morveau,againft which the following objections may beurged.
i. Allowing the author all his facts, thereappears to be an effential error in his calcula-tions. The carbonic acid as eftimated by himfrom the carbonat of barytes produced is === 42centigrammes, and the carbonic acid indicatedin the refidual gas by the teft of ammonia,amounts to 448 centimetres more;now 42 centigrammes = 6.48 grains
448 centimetres of carb. acid = 8.21
1469 grains
troy, being the total amount of carbonic acid.The quantity of diamond employed was = 200millegrammes (3.08 grs. troy;; therefore : 14.69grs. carb. a. : 3.08 grs. diamond : : 100 : 20.9.Hence the proportions of diamond and oxygenin carbonic acid, inftead of being as M. Morveauftates, 17.88 diamond and 82.12 oxygen, oughtto be reckoned at 20.9 diamond and 79.1 oxy-gen. But there will be a ftill nearer approxi-mation to the proportions laid down by Mr.Tennant, if inftead of eftimating the carbonicacid from the carbonat of barytes and the quan-tity contained in the refidual gas, we take as thebails of our calculations the quantity of oxygenconfumed. Now this, according to Morveau,amounted to 677 centimetres, or 26.6 cubicinches; the weight of which, eftimating thefpecific gravity of oxygen at .0013562, is= 9.12 grs. troy, and this added to 3.08 grs.the weight of the diamond, reduces the quan-tity of carbonic acid to 12.2 grs. inftead of14.69 as deduced from the former method.Therefore 1 part diamond requires 2.96 oxygento produce 3.96 carbonic acid : hence zoo partscarbonic acid are compofed of25 diamond75 oxygen
100
which is not very different from Mr. Tennant’sfecond experiment, in which 1.5 gr. diamondyielded 6.18 ounce meafures of carbonic acid,whence the proportions would be27.4 diamond72.6 oxygen
100.0 carbonic acid.
2. M, Morveau appears to have proceeded on
* Memoirs de Chimie, ii p. 456.
erroneous 'grounds in his eftimate of the car-bonic acid contained in carbonat of barytes.M. Pelletier' ftates the component parts of thenative carbonat of barytes at
22 carbonic acid62 barytes16 water
100
without, however, particularizing the experi-ments from which he obtained this refult. ButKlaproth from a feries of unexceptionable ex-periments' 1 has clearly Ihown, that the nativecarbonat of barytes contains no water, and con-lifts of
22 carbonic acid78 barytes
100
Now M. Morveau’s carbonated barytes was ar*.tificial , and dried only at 212 0 , therefore itdoubtlefs contained a confiderable quantity ofwater; and 22 per cent, muft be a greatly ex-aggerated ftatement of its carbonic acid.
3. The experiments of Scheele which arebrought to countenance thefe refults are by nomeans fufficiently accurate for the purpofe: con-cerning the firft, this able chemift Amply ftates,that “ five parts of nitre are fufficient to decom-“ pofe one of charcoal; whereas ten parts of“ nitre are required to produce the fame effect“ upon one part of plumbago.”' Now, whenit is confidered that in thefe experiments thenitre and charcoal or plumbago were levigatedtogether, and then projected into a red hotcrucible, it will be obvious that the differenceobferved between the plumbago and charcoalis in a great meafure owing to the fuperior fpe-cific gravity of the former, by which it wasprevented from being thrown out during thedetonation. With regard to Scheele ’s fecondexperiment, not to mention the imperfection ofthe apparatus, which confided merely of a glafsretort with a bladder fattened to it; and thatneither the temperature nor barometrical pref-fure of the gas was noticed, nor the carbonicacid which remained in combination with thealkaline refiduum of the nitre, — overlookingall thefe objections, and taking the proportionsas Hated by Morveau, they will be found if theyprove any thing, to prove too much. 80 centi-grammes of plumbago afforded, faysM.Morveau,357 cubic centimetre* of carbonic acid; there-
' Effays, p. *47.
1 Analyt. Eff, i, p. J»3.