Mr . Keir’s Experiments and Obfervattons on 
giflicated quality by addition of a little fpirit of wine, or by 
difiillation with any inflammable fubftance. 
3. No two fubftances are more frequently in the hands of 
chemifts and artifts than vitriolic acid and nitre , )et I have 
found, that a mere mixture of thefe, when much concen- 
trated, poffeffes properties which neither the vitriolic acid nor 
the nitrous, of the fame degree of concentration, have imgly, 
and which could not eaflly be deduced, a priori , by lealoning 
from our prefent knowledge of the theory of chemifhy. 
4. Having found by fome previous trials that a mixture 
compofed of nitre diflolved in oil of vitriol was capable of 
diffolving filver eaflly and copioufly, while it did not affect 
copper, iron, lead, regulus of cobalt, gold, and platina, I 
conceived, that it might be ufeful in fome cafes of the parting 
of filver from copper and the other metals above mentioned , 
and having alfo obferved, that the diflolving powers of the mix- 
ture of vitriolic and nitron s acids varied greatly in different 
degrees of concentration and phlogiftication, i thought that an 
mveftigation of thefe effects might be a fubjeft fit fot philo- 
fophical chemiftry, and might tend to illuftrate the theory of 
the diffolution of metals in acids. With thefe views I made 
the following experiments. 
3. I put into a long- necked retort, the contents of which, 
including the neck, were 1400 grain meafures, 100 gram 
meafures of oil of vitriol of the ufual deniity at which it is 
prepared in England, that is, whofe fpecifi c gravity is to that 
of water as 1,844 to 1, and ico grains of pure and clean 
nitre, which was then diiTolved in the acid by the heat of a 
water-bath. To this mixture 100 grains of ftandard filver 
were added ; the retort was let in a water hath, in. which the 
