the Dijfolution oj Metals in Acids., 373 
the remaining liquor diffolved 5 grains of copper, while 8co 
meafures of nitrous gas were thrown into the retort. 
28. The following fails principally are eftablifhed by the 
preceding experiments. 
1. That a mixture of the vitriolic and nitrous acids in a 
» 
concentrated ftate has a peculiar faculty of diffolving filver 
copioufly. 
2. That it ails upon, and principally calcines, tin, mer- 
cury, and nickel; the latter of which, however, it diflblves 
in fmall quantity, and that it has little or no ailion on other 
metals. 
3. That the quantity of gas produced while the metal is 
diffolving is greater, relatively to the quantity of metal dif- 
folved, when the proportion of nitre to the vitriolic acid is 
fmall than when it is large ; and that when the metals are dif- 
folved by mixtures containing much nitre, and with a fmall 
produftion of gas, the folution itfelf, or the metallic fait formed 
in it, yields abundance of gas when mixed with water. 
4. That dilution with water renders the concentrated mix- 
ture lefs capable of diffolving fiver, but more capable of afling 
on other metals. 
5. That this mixture of highly concentrated vitriolic and 
nitrous acids acquires a purple or violet colour when phlogifti- 
cated, either by addition of inflammable fubftances as fulphur,. 
or by its aflion on metals, or by very ftrong impregnation of 
oil of vitriol with nitrous gas 
% Dr. Priestley has noticed this colour communicated to oil of vitriol by- 
impregnation with nitrous gas or vapour, and alfo the effervefcence produced by- 
adding water to this impregnated liquor® See Experiments and Obfervations, 
V0I..III. p. 129 and 2,1 J. 
6 
6, That 
