VOL. LXXXtl.] PHILOSOPHICAL TRANSACTIONS. 227 



with alkali and glass, and some phosphoric selenite remained dissolved in the 

 liquid. Supposing the whole of the charcoal formed in this experiment to be 

 united to respirable air, the quantity of carbonic acid composed may be calculated 

 to be 104 gr.; for 32 gr. of charcoal combined with 72 of respirable air compose 

 104 gr. of carbonic acid, or 70 oz. measures; to which must be added the 25 

 oz. measures of undecom pounded carbonic acid separated. Then the quantity 

 of this dastic fluid, calculated to be decompounded, and remaining united in 

 about 400 gr. of mild fossil alkali, is 95 oz. measures, and the quantity of it 

 actually found to exist in an equal weight of alkali, was about 112 oz, measures: 

 therefore the quantity of charcoal produced does not differ very considerably from 

 that calculated to be contained in the carbonic acid decompounded. But future 

 experiments must determine whether there is a like coincidence with respect to 

 the other supposed constituent of carbonic acid, namely, respirable air. 



I deem it unnecessary to relate a number of experiments which I have made, 

 the result of which was similar to the preceding one; but it may be proper to 

 mention, that in every instance, the proportions of phosphoric acid and charcoal 

 were inversely as the quantity of carbonic acid remaining in the alkali; and that 

 the quantities of these two products diminished as the quantity above-mentioned 

 of phosphorus was diminished; accordingly, the alkali most exposed to the phos 

 phorus contained the greatest proportion of charcoal. 



I made this experiment several times with alkali, which contained a good deal 

 of water, and then I obtained a large quantity of air, which smelt of phosphorus, 

 but did not explode on contact with atmospheric air; it contained no carbonic 

 acid, nor phlogisticated air, excepting a few oz. measures in the first jar that 

 came over, but it exploded loudly when mixed with an equal bulk of dephlogis- 

 ticated air, on applying a lighted wax taper. A charge of 95 gr. of phosphorus, 

 and 540 gr. of the above alkali, afforded 206 oz. measures of this inflammable 

 air, which was of the same quality whether it was received over water or quick- 

 silver. This air I apprehend was produced by the decomposition of the water in 

 the alkali, in consequence of the superior affinity between phosphorus and res- 

 pirable air, to the affinity between respirable and inflammable air. Therefore 

 when moist alkali is used, caet. par. more phosphoric acid will be formed than 

 when dry alkali is employed; and in calculating the quantity of respirable air 

 formed, regard must be paid to the decomposition of water. It appears also, 

 that it requires less heat to decompound water by phosphorus, than to disunite 

 carbonic acid from fixed alkali. 



In these experiments I frequently used thick white glass tubes, and applied 

 heat for a long time, to the degree of rendering them flexible: when cold, I 

 found the internal surface in contact with the black alkaline matter full of cells, 

 or small cavities, and rough, to which small grains of lead adhered, consequently 



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