y'2 Mr. kirwan’s Experiments and Obfervations on 
nity which thefe calces bear to that portion of phlogifton 
which they muft lofe before they can unite to the acid, as may 
be feen by infpe&ing the table ; but all other metallic fub- 
ftances unite to this acid only where it is concentrated and 
heated. 
Of J elutions in the nitrous acid . 
The nitrous acid has lefs affinity to all metallic fubftances 
than either the vitriolic or marine. It has alfo lefs affinity to 
them than they have to that portion of phlogifton which they 
mult lofe before they can unite to it ; yet it diffolves them all 
(gold and platina excepted) even without the aid of heat be- 
caufe it unites itfelf to phlogifton unlefs too dilute; and the 
heat produced by its union with phlogifton is fufficient to 
promote the folution. 
But if it be too concentrated, it will not act either on lead 
or fiver, without the affiftance of heat, as boyle and boer- 
haave have remarked* ; for the difference betwixt its affinity 
to thefe metals, and that of thefe metals to the portion of 
phlogifton which they muft lofe before they can unite to it, is 
very great ; and when it is very concentrated, the liquor does 
not contain fire enough to throw the phlogifton and it into an 
aerial form, and reduce the folid to a liquid ; the fame would 
probably be obferved with regard to mercury, if it had not 
been already in a liquid (fate, stahl lias alfo remarked, that 
it produces very little heat in diflolving filver, and none in dif- 
folving lead or mercury f- This is eafily explained, now that 
we know that filver contains but little phlogifton, and lead 
much Ids, the heat being evidently produced, according to the 
* i s haw’s boerh. 508. 2 s h.mv’s boyi.e 335. 
f stahl fur les fels 168. 
I 
law 
