the Dilution of Metals in Acids. 37 1 
from the folutlon. The folution of filver, when faturated and 
undiluted, congeals readily in cool temperatures, and, when 
diluted to a certain degree with water, gives foliated cryftals. 
23. In the fame apparatus, and in the fame manner, 100 
grain-meafures of this impregnated oil of vitriol were applied 
to iron. An effervefcence appeared without application of 
heat, the furface of the iron acquired a beautiful rofe colour or 
rednefs mixed with purple : and this colour gradually pervaded 
the whole liquor, but difappeared on keeping the retort fome 
time in hot water. Notwithftanding a confiderable apparent 
effervefcence, the quantity of air expelled into the inverted jar 
was only 400 grain-meafures, of which \ was nitrous* and 
the reft phlogifticated. The folution was then poured out of 
the retort, and the iron was found to have loft only two grains 
in weight. The folution was returned into the retort, without 
the iron, and 200 grains of water were added to it; upon 
which a white powder was immediately precipitated, which 
re-diflolved with great effervefcence. When 2000 grain-mea- 
fures of nitrous gas had been expelled into the inverted jar 9 
without application of heat, the retort was placed in the water- 
bath, the heat of which rendered the effervefcence fo ftrong, 
that the liquor boiled over the neck of the retort, io that thw 
quantity of gas extricated could not be afcertained. 
24. In the fame manner 1 1 grains of copper were diffolved 
in 100 grain-meafures of impregnated oil of vitiiol. The fo* 
lution was of a deep violet colour, and at laft was turbid. The 
quantity of nitrous gas expelled into the inverted jar during 
the operation was 4700 grain-meafures. When the copper 
was removed, and 200 grains of water were added to the folu- 
tion, an effervefcence took place, 1700 grain-meafuies of 
C c c 2 nitrous 
