SILVERING GLASS BY GUN-COTTON. 
65 
cially as the air has no access through the spout through 
which the melted amber flows. Neither will the oil 
through which the melted amber flows be liable to take 
fire, for it does not require to be heated to a very high tem- 
perature; as is at present the practice, — the amber being 
now melted and dissolved in oil heated to the point of vio- 
lent ebullition. And further, the chafing dish is small, and 
it is impossible it can communicate to the vessel filled with 
oil (which is of much more considerable capacity) sufficient 
heat to cause fear of fire. 
4th. All the vessels are of stout copper, and consequently 
are not liable to burst, as is the case with the earthen ones, 
which are at present too often employed. 
It will thus be seen, that, independently of the practical ad- 
vantages which this method of manufacturing varnish (and 
which has already stood the test of long experience) pos- 
sesses over those ordinarily in use, it has the important one 
of being unattended with danger. — Pharm. Journ., Sept., 
1S49, from the Technologist e, as translated in the London 
Journal. 
ART. XT.— MODE OF SILVERING GLASS BY THE EMPLOY- 
MENT OF GUN-COTTON. 
M. Vohl has recently discovered that a solution of gun-cot- 
ton in a caustic ley possesses in a high degree the property of 
precipitating silver from its solutions in the metallic form. 
In fact, on bringing gun-cotton into contact with a caustic 
ley of sufficient strength, the cotton will become dissolved 
in the ley, giving out ammonia with a considerable degree 
of heat, and producing a deep brown liquid, somewhat 
thick. On pouring an acid into this, a brisk effervescence 
is producer], carbonic acid and nitrous acid being disen- 
gaged. 
6* 
