336 PHILOSOPHICAL TRANSACTIONS. [ANNO 1783. 



inversely as the affinity of each basis to such acid. 2dly, That the quantity of 

 each basis, requisite to saturate a given quantity of each acid, is directly as the 

 affinity of such acid to each basis. Thus 100 gr>. of each of the acids require 

 for their saturation a greater quantity of fixed alkali than of calcareous earths, 

 more of this earth than of volatile alkali, more of this alkali than of magnesia, 

 and more of magnesia than of earth of alum, as may be seen in the following 

 table. 



Quantity of basis taken up by 1 00 grs. of each of the mineral acids. 



Veg. fixed Mineral Calcareous Volatile Mag- Earth of 



alkali. alkali. earth. alkali. nesia. alum. 



Grs. Grs. Grs. Grs. Grs. Grs 



Vitriolic acid 'J 15 Hi5 110 yo Su 75 



Nitrous acid 215 165 96 87 75 6"5 



Marine acid 215 158 89 79 71 55 



As these numbers agree with what common experience teaches us concerning 

 the affinity of these acids with their respective bases, they may be considered as 

 adequate expressions of the quantity of that affinity, and I shall in future use 

 them as such. Thus the affinity of the vitriolic acid to fixed vegetable alkali, 

 that is, the force with which they unite, or tend to unite, to each other, is to 

 the affinity with which that same acid unites to calcareous earth, as 215 grs. to 

 1 10; and to that which the nitrous acid bears to calcareous earth as 215 grs. to 

 96, &c. 



Of' the affinity of the mineral acids to metallic substances. — Having established 

 the agreement between the quantity of any alkaline or terrene basis, taken up at 

 the point of saturation by a given weight of any of the 3 mineral acids, and 

 the quantity of affinity which each of these acids bears to such basis, I naturally 

 extended my views to metallic substances, to try whether this coincidence could 

 be traced with regard to them also; but the difficulties that occurred in this in- 

 quiry were so great, that the same degree of certainty must not be expected as 

 in the foregoing part. 



Metallic substances, when freest from all foreign mixture, are obtained either 

 in a reguline state, or in that of a calx. These calces, if formed by fire, are 

 constantly combined with more or less of the aerial acid, which is very difficultly 

 extracted from them, and very soon re-absorbed ; and if formed by solution, 

 they as constantly retain a portion of their solvent or precipitant, so that the 

 precise weight of the really metallic part is difficultly ascertained. But though 

 this should easily be effected, still they would for the most part be unfit for my 

 purpose; because most of them, when much dephlogisticated, arc insoluble in 

 some or all the acids: hence I chose metals in their metallic state for the subject 

 of my experiments. These consist of specifically different earths and phlogiston, 

 and of this they must lose a part before they can be dissolved in acids; but, be- 



