METALS. 
59 
battery, silver or gold is deposited. This is electro-plating. To 
prevent the silver from presenting a granular or dead appear- 
ance, a few drops of bisulphide of carbon may be added to the 
solution. 
The botanical specimens, &c., of which there are exhibited 
electrotype coatings, may be prepared by first dipping the 
grass or leaves into a solution of phosphorus in bisulphide of 
carbon, and then plunging the article into a solution of nitrate 
of silver. The thin film of phosphorus left upon the surface 
occasions a precipitation of a finely-divided coat of silver, upon 
which, when connected with the battery and placed in the 
proper solutions, any quantity of either copper, silver, or gold 
can be deposited. 
Some of the most interesting results of electro-metallurgy 
have been the coating of iron with copper, and the electro- 
chemical deposition of the compound metal, brass, of which 
some examples are shown. An important application of electro- 
metallurgy on a large scale has been the electro-deposition of 
nickel or various metals. The nickel may be thrown down 
from a solution of a double salt, such as a double sulphate of 
nickel and ammonia. The process is now largely worked in 
London and Birmingham, and specimens are exhibited, showing 
the deposition of nickel on slabs of copper, tin, cast-iron, steel, 
brass, and German silver. 
Phosphor-Bronze. —The upper shelves of this Case (No. 32), 
on the opposite side to that containing the electro-metallurgical 
series, are devoted to the exhibition of specimens of this alloy, 
presented by the Phosphor-bronze Co., Limited. Experiments 
have shown that the alloy formed by adding phosphorus to 
bronze in certain proportions, possesses valuable mechanical pro- 
perties ; and its manufacture has consequently been established 
in this country. The manifold applications of phosphor-bronze 
are well illustrated by the specimens exhibited in the case 
before us. 
Chinese Bronzes, &c. Case No, 36. 
The Chinese and Japanese exhibit very great ingenuity in the 
preparation of alloys, and in their modes of casting. In many 
instances the model is most carefully made in wax, and all the 
ornamentation, inscriptions, and the like elaborately finished ; 
this is then covered with the clay which is to form the mould, 
and when dry the wax is melted out ; the metal which subse- 
quently in a fluid state supplies its place fills every part, and 
thus is obtained a casting of great sharpness and correctness. 
Casting by the cire perdu process is now practised in this country. 
The gongs and tam-tams of the Chinese are forged with 
the hammer, as indeed are many of their bronze articles. The 
composition of these appears to be 82 per cent, of copper 
and 17 of tin, with small quantities of iron and nickel. The most 
celebrated locality for making gongs is Su-tchou. 
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