On a new Method of obtaining pure Silver. 205 
But admitting that there is a newly prepared sulphate at hand, 
when its solution is mixed with the nitrate of silver, an addi- 
‘tional dose of oxygen is at once presented to the iron. When 
the precipitated silver is collected on the filter, there will be found 
in it a quantity ef sub-oxysulphate of iron, which, if care be 
taken, can be made by its specific levity to oceupy the stratum 
above the silver. 
Another defect in this process is, that the silver is not entirely 
recovered. If the solution of oxysulphate of iron, from which the 
silver has heen filtered, be mixed with solution of salt, there will 
be a copicus precipitation of muriate of silver. This happens even 
when a large quantity of sulphate of iron has heen employed: 
and in these cases, an additional quantity seems to have no ef- 
fect, with such force do the last portions of silver retain their 
oxygen. Thus the defects of this process are, that it presup- 
poses the recent preparation of sulphate of iron; that the silver 
is not entirely recovered ; and that what is recovered is not quite 
pure. 
The formation of the arbor Diane is obviously under the ob- 
jection of tediousness and trouble. 
The defects of these processes compelled me to try several 
methods for obtaining pure silver. The following appears to an- 
swer expectation : 
240 grains of standard silver are to be dissolved in as much 
pure nitric acid of s.G. about 1-2, as will be barely necessary 
for the solution. This is to be filtered, and distilled water al- 
Jowed to run through the filter until the fluids amount to two 
ounces measure. A bright plate of copper weighing more than 
64 grains is to bé immersed, and frequently agitated in it. When 
the silver has entirely precipitated, which will very soon happen, 
the clear supernatant liquor is to be poured off, and the preci- 
pitate is to be well washed. The silver is then to be boiled for 
a few minutes in liquid ammonia: it is to be again well washed, 
and dried on a filter. 
A few remarks to show the adequacy of this process may be 
necessary. 
The silver of commerce is composed of 37 of fine silver to 3 of 
eopper. The fine silver is obtained by cuppellation, and there- 
fore contains gold. When this silver is dissolved, the gold is 
found in the form of a powder. I have sometimes observed it 
black and sometimes purple: that is, it is either peroxide or 
protoxide. In the nitrous solution we have therefore only silver 
and copper, unless we regard the very small quantity of gold 
_ which nitrous acid can dissolve. 
When into the solution of standard silver we immerse a plate 
of copper, the latter dissolves in place of the silver, which is 
therefore 
