204 On a new Method of obtaining pure Silver. 
stina, by M. Menager; the Arch of Titus, by M. Guenepin 3 
the Temple of Fortune at Preneste, by M. Huyot; and of the 
Pantheon, by M. Leclerc; to which we may also add the re- 
storations of the Portico of Octavius, by M. Chatillon, and the 
Temple of Mars the Avenger, by M. Gauthier. 
It only remains, therefore, for us to solicit the minister of the 
interior to supply the funds for engraving these splendid re- 
mains of ancient architecture, to enable us to outstrip the career 
of other nations, 
XLVI. Ona new Method of obtaining pure Silver ; with Oblser- 
vations on the Defects of former Processes. By M. Do- 
NoVAN, Esq.* 
Tuere have been four principal methods proposed for obtain- 
ing pure silver. The first is by cuppellation; the second, by 
the reduction of /una cornea; the third, by precipitating silver 
from its nitrous solution by sulphate of iron; the fourth, by 
means of that symmetrical precipitation called arbor Diane. 
These different modes labour under defects. They are either 
inconvenient, incertain, tedious, unceconomical, or inadequate. 
In the process of cuppellation, it is true that all the base me- 
tals are carried down by the lead ; but it is not thus possible to 
separate the gold: this is accordingly found in the resulting 
silver. 
The reduction of luna cornea by atkali affords when the pro- 
cess succeeds a very pure silver: but the success is doubtful, and 
for the most part fails in the hands of the inexperienced. It is 
well known that when the crucible is taken from the fire, instead 
of containing pure silver, it is often found entirely empty, so great 
is the tendency of the fused matter to pass through the pores, 
unless prevented by due skill in the operator. Another source 
of uncertainty is the degree of heat : if it he teo high, the muriate 
volatilizes: if too low, the reduction is not completed; and 
without singular good fortune, the expected quantity will in no 
ease be obtained. Beside these difficulties, the process is ex- 
ceedingly complex and troublesome. 
In the next method, a solution of nitrate of silver is mixed 
with very dilute solution of sulphate of iron: the iron acquires a 
new dose of oxygen derived from the silver; the latter is there- 
fore precipitated. Unless the sulphate of iron he recently pre- 
pared, it will not have the strong attraction to oxygen necessary 5 
and either little silver will be obtained, or none. 
* Read in the Kirwanian Society, February 7, 1816. 
But 
