VOL. LXXXII.] PHILOSOPHICAL TRANSACTIONS. 223 



there was a deficiency of this elastic fluid, and that the charcoal and phosphoric 

 acid corresponded to this deficiency. Accordingly some chemists have conjec- 

 tured that the small quantity of charcoal afforded in this experiment pre-existed 

 in the phosphorus, which, it is well known, is distilled from charcoal; and 

 others have suspected that it might have arisen from accidental impurities. 



As experience also has taught us that phosphorated mineral alkali will not yield 

 phosphorus by exposure to charcoal and heat, unless plumbum corneum be added, 

 we cannot infer that the carbonic acid in mild mineral alkali will be decom- 

 pounded by phosphorus; because, as in the case of bone-ashes and phosphorus, 

 the joint affinities between respirable air and phosphorus, and between phosphoric 

 acid and mineral alkali, are, by this fact, shown to be not inferior to the con- 

 joined affinities between charcoal and respirable air, and between carbonic acid 

 and that alkali. No other conclusion can be drawn with respect to the affinities 

 exerted when charcoal is applied to phosphorated vegetable alkali; because the 

 affinity is stronger between the phosphoric acid and vegetable alkali, than be- 

 tween the same acid and mineral alkali. As the attractive forces between phos- 

 phoric acid and barytes, and between that acid and magnesia are, very probably, 

 at least equal to those between phosphoric acid and fixed alkalis, the question, 

 whether carbonic acid united to these earths can be decomposed by phosphorus, 

 remains to be determined by experiments. But with respect to the volatile alkali, 

 we know, by the experience of making phosphorus from urine, that tlie united 

 affinities between respirable air and phosphorus, and between phosphoric acid and 

 volatile alkali, are inferior to the joint affinities between charcoal and respirable 

 air, and carbonic acid and volatile alkali; hence, in a due degree of heat, phos- 

 phorus and mild volatile alkali are formed from phosphorated volatile alkali and 

 charcoal, consequently carbonic acid combined with volatile alkali, cannot be 

 decompounded by phosphorus and heat, even if the volatility of that alkali did 

 not, apparently, render it impossible to apply the requisite degree of heat. We 

 know so little of the degree of chemical attraction between clay and phosphoric 

 acid, that the question, whether carbonic acid united to clay will be decom- 

 pounded by phosphorus? can only be answered by future experiments. 



As I presume that I have made experiments which enable us to draw conclu- 

 sions concerning the above cases of compound attraction, and which also show, 

 in several instances, that carbonic acid is decompounded, and affords respirable 

 air, and charcoal; I think it my duty, on a subject so very interesting in the pre- 

 sent state of chemistry, to submit them to the consideration of this Society. 



Experiments ivith phosphorus, applied to mild fossil alhali. — I began with at- 

 tempting to decompound carbonic acid in union with fossil alkali, in preference 

 to the same substance combined with quick-lime, because tlie proportion of this 

 elastic fluid is much greater in mild fossil alkali than in calcareous earth, because 



