20 Mr. k i S wan’s Experiments and Observations on 
■ . , * .ft „ f r> » , 
.n . . * ' 1 £ ' ; 1 
Copper in marine acid. 
' i . i ! ' ) 7ll 
loo grs. of copper require 1190 grs. of real marine acid to 
diflblve them, and alfo the affiffance of a moderate heat, the 
proportion of acid to that of water being as 1 to 4J., that is, 
its fpecific gravity being 1,186, if a greater heat he ufed, more 
of the acid will be requifite, as much will be diffipated. If the 
acid be more concentrated, it will a£t more vigoroufly. 
In my laffpaperl mentioned, that 85 grs. of copper afforded 
86 of marine air: however, I muff now add a circumffance 
which I then did not attend to, which is, that the mercury 
over which that air was received was a£Iedupon, fo that part of 
the air was due to this action, which invalidates the conclufion 
I there drew concerning the quantity of phlogiffon in marine 
air, which hence appears to be greater than I there eflimated it. 
The calces of copper are alfo folublein this acid, though not 
fo eafily as in the nitrous acid. 
Tin in the vitriolic acid. 
100 grs. of tin require for their perfefl folution 872 grs. of 
real vitriolic acid, whofe proportion to water fhould not be leis 
than as 1. to .JL, and alfo the affiffance of a ffrong heat; when 
the adion of the acid has ceafed, fome hot water fhould be 
added to the turbid lolution, and the whole again heated.. This 
folution affords 70 cubic inches of inflammable air. Tin is alfo 
foluble in a more dilute acid, but not in fo great quantity. 
The calces of tin (except that precipitated from marine acid 
by fixed alkalies) are infoluble in this acid. 
Tin 
