1811.] On the Cause of Chemical Proportiom. B9 



that boracic acid contains 73*18 per cent, of oxygen, and that 

 these 73- 18 constitute two volumes. The acid, then, is B + 2 O j 

 and a volume of radicle must weigh 73 "273. 



6. Carionicum, carbon (C). — M. Biot has ascertained by delicate 

 and exact experiments that the specific gravity of oxygen, compared 

 with that of atmospherical air, is 1'10359 to 1; and that the 

 weight of the same volume of carbonic acid gas is 1-5 1961. Hence 

 it follows that carbonic acid is; composed of 7i^"62 of oxygen and 

 2'J''iS of carbon. M. de Saussure has determined the weight of 

 oxygen gas 1-10562, from which it follows that carbonic acid 

 ought to contain 72*75 of oxygen ; and, finally, Saussure found, by 

 a direct experiment, that when very pure ch.ircoal, obtained by 

 exposing oil of rosemary to a strong heat, is employed, 27*12 parts 

 of charcoal form lOO of carbonic acid, which ought, therefore, to 

 contain 72*88 of oxygen. On the other hand, we know already that 

 in the carbonates the acid contains either twice or four times as 

 much acid as the base. From this it follows that carbonic acid 

 ouL'-ht to contain either 2 or 4 volumes of oxygen. The circumstance 

 that carbonic acid gas contains exactly four times as much oxygen 

 as the same bulk of ammonia, appears very favourable to the opinion 

 that carbonic acid contains four volumes of oxygen. But there are 

 other considerations which render that idea less probable. We 

 know, for example, that oxygen gas, in combining with the quan- 

 tity of carbon requisite to produce carbonic oxide, doubles exactly 

 its ordinary volume. It appears here reasonable to think that fhe 

 additional volume is carbon ; for it is contrary to the experiments 

 hitherto made to suppose that oxygen gas in combining with half its 

 A'olume of carbon should experience an expansion equal to the half 

 of its own volume. We know several examples where two gases 

 combine without undergoing any contraction in their volume : we 

 know likewise a great many instances where two gases in combining 

 contract half their volunie, or even more; but, as far as I know, 

 wc arc not acquainted with any example of two gaseous bodies 

 dilating v\ hen they combine. Hence we must conclude that car- 

 bonic oxide is C + O, and carbonic acid C + 2 O. Besides, if we 

 consider the imperfectly acid properties of carbonic acid, it is 

 reasonable to consider as supercarhonates those combinations in 

 which the acid contains four times as much oxygen as the base ; 

 and as neutral carbonates, those in which it contains twice as much 

 oxygen as the base, as the carhonates of lime, barytes, lead, &c. (I 

 refer here to what 1 have already said on tliis subject in the Ann. de 

 Chim. Stpt. ISll, p. 264.) 



Although the determinations of the composition of this acid 

 stated above must be very exact, it appeared to me that a verification 

 by means of an analysis of carbonate of lead, would be very inte- 

 resting. 1 found, however, tliat the analysis of this salt, thougii 

 extrcini-Iy simple, is attended with diHiculties which render it less 

 exact than the determinations above staled. 'J'hcsc diflicultics are 

 owing to the great readiness with wliich carbonate of lead combines 

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