The ferrotype and how to make it - The Grian Press

74 THE FERROTYPE.
allowing the sediment to fall to the bottom before
decanting the liquid.
You have now in the washed precipitate a
grayish powder, which is comparatively pure
metallic silver, which, if you choose, may be
converted into solution again by adding nitric
acid sufficient to re-dissolve, or the precipitate
may be dried and placed in a crucible with a
small quantity of nitrate of potash, and fused
the potash will remove any trace of iron or zinc.
I have by this method converted an old and use-
less solution of silver into a good working bath
in a very short time, although it is better not to
do it in a hurry.
Nitrate of silver may also be reduced from
solution by evaporating to dryness ; at the last,
the heat should be very gentle, because in the
presence of organic matter the nitrate is easily
changed to pure silver, which would require to
be re-dissolved.
The fused mass presents a yellowish appear-
ance, and readily dissolves in water, leaving the
organic matter and residues of cadmium and po-
tassium in a thick, pasty mass of a dark color,
but which also contains some silver, and on that
account should be saved with other wastes.
It has been said that the fusion of the residues
of photographer's old silver solutions is attended
with some danger from the not improbable
formation of fulminating silver, a most power-
fully explosive compound. Some idea of its ex-
;