Brass . 
127 
Is removed, drop into the water last poured off from the 
precipitate a few drops of liquid ammonia. If any of that 
sulphat be still present, the ammonia will produce a blue 
colour in the water. The silver, if not wished to be kept 
as a powder, may be melted with from a fourth to a half 
of its weight of nitrate of potash. 
The liquid sulphat of copper decanted from the precis 
pitate, as also the water employed in washing it, may af- 
terwards be evaporated in a copper basin, and, by crystal- 
lization, a quantity of blue vitriol equivalent to the cost of 
the acid will be obtained. 
Should some parts of the alloy, by accideiit, have re- 
mained undissolved, they may be separated by decanta- 
tion, and reserved for the next repetition of the process. 
[21 Phil. Mag . 352, 
This process is somewhat of a kin to that discover- 
ed by James Keir, Esq. of Birmingham. Take IGlbs. 
of oil of vitriol : dissolve in it ilb. of nitre. This mix- 
ture will in a moderate warmth or even in the temperature 
of a warm day, dissolve silver, when undiluted : it will 
not dissolve gold, platina, iron, zinc, or nickel, unless it 
be diluted. This is an useful, because a cheap process. 
Aqua regia made with nitric acid is dear comparatively. 
ON ROLLING COPPER INTO PLATES. 
The following method of rolling Copper into plates , as 
practised at the extensive works at Taybach , in Wales , 
is taken from Donovan 1 s Tour through South Wales 
and Monmouthshire . 
BEFORE the copper is converted into plates or bars, 
the pig of metal is made red hot, when it is closely beat- 
en together under the hammer, and cut into pieces of the 
most convenient length for the purpose wanted, by shears 
.moved by a wheel. Again, those pieces are conveyed to 
the furnace when they become red hot as at first. One 
