the Attractive Powers of Mineral Acids. 65 
reduced during the cxpulfion of its air; fecondly, that the 
quantity of the phlogiflon in the inflammable air may have 
been greater as this varies with its temperature, and the weight 
of the atmofphere ; fo that upon the whole thefe experiments 
confirm the refults exprefl'ed in the table. 
Of the affinity of metallic calces to phlogiflon. 
That inflammable air or phlogiflon is conden fed to a very 
confiderable degree by uniting to any metallic fubflance, fo that 
its fpecific gravity is not only equal, but much luperior, to that 
of the metallic earth with which it combines, may eafily be 
concluded from the example of fixed air, which, by uniting to 
calcareous earth, acquires a fpeciflc gravity equal to that of 
gold ; and hence, that metallic earth which condenfcs phlo- 
giflon mod, and in greatefl: quantity, uniting to it mod clofely, 
may be laid to have the greatefl: affinity to it ; fo that if we 
could find the fpecific gravity of a calx perfectly pure, both 
from phlogiflon and fixed air, we could, by comparing its den- 
lity with that of the fame calx when metallized, know the 
denfity which phlogiflon acquires by its union with fuch calx ; 
but to procure fuch calces hath hitherto proved impoffihle, as, 
during their dephlogillication, they combine with fixed air, or 
fome particles of their menftruum ; and hence their abfolute 
weight is increafed, though their fpecific gravity be fomewhat 
diminifhed. From this lafl circumflance it appears, that the fpe- 
cific gravity of calces differs much lefs from that of their reflec- 
tive metals than docs the fpecific gravity which the phlogiflon 
acquires by its union with thofe calces, from that which it 
poflefles in its uncombined flate ; in the fame manner as the 
denfity of quick-lime differs much lefs from that of lime- 
ilone, than does the denfity which fixed air acquires by its 
Vol. LXX 1 II. " K union 
