1 6 Mr. kir wan’s Experiments and Obfervalions concerning 
Solution of iron in the vitriolic acid . 
100 grs. of bar-iron, in the temperature of 56°, require for 
their folution, 190 grs. of real acid, whole proportion to that 
of the water with which it Ihould be diluted, is as 1 to 8, jo, 
or 12. It would acl on iron, though its proportion were 
greater or Idler, but not fo vigouroufly. If towards the end a 
heat of 200° were applied, 1 23 grs. of real acid would be 
fufficient. 
The air produced hy this folution is intirely inflammable, and 
generally amounts to 155 cubic inches. 
Iron is alfo foluble with the afliftance of a ffrong heat, and 
in fmaller quantity in concentrated vitriolic acid ; and in this 
cafe fcarce any inflammable air is produced, but a large quan- 
tity of vitriolic air as Dr. priestley has obferved, and afmall 
quantity of lulphur fublimes at the latter end. This fad is a 
clear refutation of Mr. Lavoisier’s hypothecs ; for is it not 
evident, that the fame fubflance which, when a dilute acid is 
ufed, goes off in the form of inflammable air, does when 
a concentrated acid is ufed, to unite this acid, and thus 
form both vitriolic air and lulphur ? In the flrft cafe it 
cannot unite to the acid, by reafon of the large quantity 
of water combined with the acid ; and as the liquor, being 
moftly aqueous, contains a large quantity of fpeciflc fire, 
it receives that fire when the acid unites to the metallic 
earth, and flies off in the form of air. But in the fecond cafe, 
the concentrated acid, containing much lels l'pecific fire, can- 
not expel the phlogildon in the form of inflammable air (as 
this air abforbs a vaff quantity of fire) but unites to it, when 
by heat it is further ffripped of its water, and thus forms both 
100 
