64 Mr. Keik’s Experiments and Obfervations on 
any fenfible effervefcence, or fuffer a greater lofs of weight 
than two grains. , . r . 
7 . In the fame apparatus too grains of ftandard filver were 
expofed' to a mixture of 30 grains of nitre diflolved m _oo 
grain -meafures of oil of vitriol; and in this operation, 80 
grains of filver were diflolved, while at the lame time 45 ^ 
Lin-meafures of nitrous gas were thrown into the inverted 
kr. When the undiffolved filver was removed, 200 g.ams of 
water were added to the folution, which was of a violet co- 
lour, and upon the mixture of the two fluids an efferves- 
cence happened ; but only a few bubbles of nitrous gas were 
""I Tthellm. apparatus too grains of ftandard filver wero 
expofed to a mixture of zoo grain- meafu res ot oil of viti.ol, 
200 grains of nitre, and 200 grains of water ; and m ns 
operation 20 grains of the filver were diffolved without any 
fenfible emiffion of air or gas. # , *3 
o In thefe experiments, the copper contained in the ftan 
filvei gave a reddilh colour to the faline mafs which was formed 
in the folution, and feemed to be a calx of copper interfperfed 
through the fait of filver. I perceived no other difference 
between the effects of pure and ftandard filver diflolved in this 
t 
"I I then expofed tin to the fame mixture of oil of vitriol 
and nitre, In the fame apparatus, and in the to arcumftances, 
taking care always to add more metal than could be diffolved, 
that by weighing the remainder, the quantity capable of being 
diffolved might be found, as I had done with the experiments on 
filver : and the refults were as follow. 
, , No tin was diffolved nor calcined by the mixtures in the. 
proportion of aoo grain-meafores of oil of vitriol to aoo gra.no 
