The operator may now be certain that the liquid will no
longer congeal into a soft mass of silver bisulphate, which on contact
with water will disintegrate into powder, obstinately retaining a
large amount of free acid; but the silver will separate as a
monosulphate in hard and large yellow crystals retaining no acid and
preserving their physical characteristics when thrown into water.
After cooling to, say, 80 deg. F., the silver sulphate will have coated
the pan C about 1 in. thick. There will also be found a deposit of
copper sulphate when the mother acid, after having been used over and
over again, has been sufficiently saturated therewith. Lead sulphate
separates in a cloud, which, however, will hardly settle at this
stage.
The whole operation just described, which constitutes the most
essential feature of the author's improvement upon his old process
described in Dr. Percy's work, is a short one, as the acid requires by
no means great dilution. The steam has merely to furnish enough water
to dilute the free acid present to, say, 62 deg. B. Areometrical
determination is, of course, not possible, on account of the dissolved
sulphates.
_Reducing the Silver Sulphate to Fine Silver.
Pages:
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134