66 Mr. kirwan’s- Experiments and Obfervatims on 
union with quick-lime from that which belongs to it in its aerial 
fhte ; and lienee, inftead of deducing the quantity of affinity 
of metallic calces to phlogifton from the following proportion, 
viz. that the affinity oj metallic calces to phlogijlon is in a com- 
pound ratio of its quantity and denfity in each metal , I am obliged 
to deduce it from this other, viz. that the affinity of metallic 
calces to phlogijlon is direBly as the fpecific gravity oj the refpec- 
tive metals , and inversely as the quantity of calx contained in a 
given weight of thofe metals. This latter propolition is an ap- 
proximation to the former, founded on this truth, that the 
larger the quantity of phlogijlon in any metal is , the fmaller is the 
quantity of calx in a given weight of that metal ; and that the 
denfity which the phlogifon acquires , is as the fpecific gravity of 
the metal. This latter proportion, however, is not exadtly 
true, for this denfity is much greater ; yet it is the neareft 
approximation I can make, and 'its defedt is fenfible only with 
regard to thofe metals which contain a confiderable quantity of 
phlogiflon, viz. gold, copper, cobalt, and iron : with regard, 
to the reft it is of no importance. 
Then the fpecific gravity of metals being as reprefented in 
the firft column of the following table, the affinity of their 
calces to phlogifton will be as is fhewn in the fecond column,, 
The third column expreftes thefe affinities in numbers homo- 
genous with thofe which exprefs the affinities of acids with 
their balls. • * i 
Gold 
