64 
REPORT ON GILDING, ETC. 
large capsules of platinised brass, which combine cheap- 
ness with the necessary resistance to saline or acid solu- 
tions. 
Armorers will turn to account, under different forms, 
this means of preserving oxidisable and sulphurisable me- 
tals, used in the manufacture of arms. 
Platinum, thus applied, may be obtained from the crude 
solution of platinum ore, as the metals which accompany it 
do not injure the effect. This process reduces the price of 
platinum to that of silver, and seems to open for platinum, 
now but little employed, an unlimited sale, particularly in 
the manufacture of chemical products, and in the concentra- 
tion of acids (especially sulphuric acid.) 
The extensibility of platinum is such, that, by the pro- 
cesses of M. De Ruolz, 1 millegramme of platinum is capa- 
ble of uniformly covering a surface of 50 square millime- 
tres; which corresponds to a thickness of T ^- -L__ of a milli- 
metre, analogous, as is evident, to the most attenuated pel- 
licle of which we can form a just idea by direct observa- 
tion. 
Coppering. — The same process is used as for silvering, 
namely, by means of cyanuret of copper dissolved in the 
alkaline carbonates ; but the precipitation of copper is more 
difficult than that of the precious metals. 
Leading. — By acting on the solution of oxide of lead in 
potassa, by means of the pile, iron pkte, iron, and all the 
metals in general are leaded. 
The manufacture of chemical products will also be bene- 
fitted by this discovery, in thus obtaining iron boilers lined 
with lead, and in which the solidity of the iron is united 
with the resistance of lead to the chemical actions of saline 
solutions and weak acids. 
Tinning. — The new T processes may be extended in ap. 
plications, by giving an easy and prompt means of tinning 
