VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 33g 



cific gravity equal to that of gold ; and hence, that metallic earth which con 



denses phlogiston most, and in greatest quantity, uniting to it most closely, may 



be said to have the greatest affinity to it ; so that if we could find the specific 



gravity of a calx perfectly pure, both from phlogiston and fixed air, we could, 



by comparing its density with that of the same calx when metallized, know the 



density which phlogiston acquires by its union with such calx ; but to procure 



such calces has hitherto proved impossible, as, during their dephlogistication, 



they combine with fixed air, or some particles of their menstruum ; and hence 



their absolute weight is increased, though their specific gravity be somewhat 



diminished. From this last circumstance it appears, that the specific gravity of 



calces differs much less from that of their respective metals, than does the specific 



gravity which the phlogiston acquires by its union with those calces, from that 



which it possesses in its uncombined state ; in the same manner as the density 



of quick-lime differs much less from that of lime-stone, than does the density 



which fixed air acquires by its union with quick-lime from that which belongs to 



it in its aerial state ; and hence, instead of deducing the quantity of affinity of 



metallic calces to phlogiston from the following proposition, viz. that the affinity 



of metallic calces to phlogiston is in a compound ratio of its quantity and density 



in each metal, I am obliged to deduce it from this other, viz. that the affinity of 



metallic calces to phlogiston is directly as the specific gravity of the respective 



metals, and inversely as the quantity of calx contained in a given weight of those 



metals. This latter proposition is an approximation to the former, founded on 



this truth, that the larger the quantity of phlogiston in any metal is, the smaller 



is the quantity of calx in a given weight of that metal ; and that the density 



which the phlogiston acquires, is as the specific gravity of the metal. This 



latter proposition, however, is not exactly true, for this density is much greater ; 



yet it is the nearest approximation I can make, and its defect is sensible only with 



regard to those metals which contain a considerable quantity of phlogiston, viz. 



gold, copper, cobalt, and iron : with regard to the rest it is of no importance. 



Then the specific gravity of « t ^g#!£S£ a ' 



metals being,- as represented in ?° ld '9 •• °- 23 •• Wil 



° \ Mercury 14 .. 0.147 .. 012 



the 1st column ot the annexed silver 11.091 .. o.ns .. -iju 



table, the affinity of their calces L^ n - 3a •• 011 °" •• 4S3 



., • . ,, • , Copper 8.8 .. 0.109 .. «i 



to phlogiston will be as is shown Bismuth 9.6 .. 0.099 .. +12 



in the 2d column. The 3d co- CoDalt 7.7 0.092 .. 383 



., re ■ ■ I ron 7-7 . . 0.090 . . 375 



lumn expresses these affinities R eg ulus of arsenic . . 8.31 .. 0.O89 .. 370 

 in numbers homogeneous with Zinc '- 2+ •• o.osij .. 34-0 



j ... ° ,, a- ■ Nickel 7.33 .. O.0S12 .. 333 



those which express the amni- Tin 7. .. 0.075 312 



ties of acids with their basis. Regulus of antimony 6.86' .. 0.074 .. 308 



Here we see, that the calx of lead has a greater affinity to phlogiston than the 



x x 2 



