34 Afr. kirWAn’s Experiments and Obfervations on 
improvement of the arts of dying and enamelling, the pro- 
ceffes by which many of their ingredients are procured being 
at prefent much too vague. Thus the procefs at prefen t ufed 
for preparing the precipitate of cassius frequently fails, the 
ftrenpth of the acids not being; fufficiently afcertained. 
4thly, The ufes of this knowledge in the examination of 
mineral waters, and in efiaying of ores, have been amply 
proved in the elaborate treatifes which the celebrated berg- 
man has lately given us on thefe fubjefts. And I may further 
add, that the knowledge of the quantity of acid requifite for 
the folution of different metallic fubftances may alfo furnifh us 
with a new criterion for diftinguifhing them from each other, 
and the purer from their alloys, and in lome cafes inform us 
of the quantity and quality of the alloy : thus, 100 parts pure 
filver require lefs of the nitrous acid to dilfolve them than 
100 grs. of ftandard lilver ; thus alfo, by diffolving in fpirit of 
fait any metallic fubftance fufficiently foluble therein, we may 
know whether it contains the fm allelf particle of filver, quick- 
filver, or arfenic, as thefe are almoff infoluble therein, or of 
regulus of antimony, cobalt, nickel, or wifmuth, of which 
it alfo takes but a final! proportion. 
But the end which of late 1 had principally in view, was to 
afcertain and meafure the degrees of affinity or attraction that 
fubliif betwixt the mineral acids, and the various bafes with 
which they may be combined, a fubjedf of the greateff impor- 
tance, as it is upon this foundation that chymifirv, confidered as 
a fcience, muff finally reft ; and though much has been already 
done, and many general obfervations laid down on this head, 
yet fo many exceptions have occurred even to fuch of thefe 
obfervations as feemed to have been moff firmly eftablifhed, 
that not only a variety of tables of affinity have been formed, 
7 but 
