ON THE SCIENCE OP ELECTRO-PLATING. 
47 
surface is coated with copal-varnish, to prevent the gilding from 
taking place on those parts. And, finally, the articles are 
washed in clean water, and at once immersed in hot, dry saw- 
dust, which absorbs the moisture and dries them quickly, before 
they have time to tarnish. The processes of preparing and 
finishing articles are, in nearly all cases, much more troublesome 
than that of plating itself. 
These various points of information are only the outlines of 
the process of electro-plating, and for the details the reader is 
referred to the various published works on the subject. 
The scientific perfection of electro- deposition consists in its 
definite mathematical character. Under carefully prepared 
conditions, all the chemical actions that occur in the battery 
and plating-vat stand in certain precise mathematical relations 
to each other ; for every 32^ parts of zinc dissolved in each 
cell of the battery, there are 108 parts of silver dissolved and 
108 parts deposited in the vat; or if it be a copper solution, 
31 f parts of copper, or an antimony solution, 40 parts of 
antimony ; for every 32| parts of zinc dissolved in the battery, 
there are 9 parts of water decomposed, and if it be a Smeefs, or 
a common zinc and copper cell, there is 1 part of hydrogen set 
free at the negative silver or copper plate ; and similarly with all 
the chemical actions taking place in the various battery-cells and 
depositing liquids. Each action in a given circuit stands in a 
certain mathematical relation to each and all the others, and 
this is known as the law of “ definite electro-chemical action.” 
The artistic advantage of electro-deposition consists in the 
great facilities it affords for the exercise of taste and design, and 
for more accurately imitating the forms of nature, as in rocks, 
animals, fruits, trees, &c. And its domestic utility and house- 
hold economy consist in the greater degree of cleanliness and 
beauty obtained at so moderate a cost. 
As long as arts and manufactures are left to be directed and 
improved by simple experience, their progress is extremely 
slow; but directly scientific knowledge is successfully applied to 
them, they advance with astonishing speed. For years the 
manufacture of plated metal wares existed without making any 
material progress; but, on the application of science, its progress 
became surprising, and called the attention of all persons to 
the new process. 
Thirty years ago electro-plating for commercial purposes 
was unknown ; but as soon as Jacobi and Spencer made known 
the results of their electrical experiments upon metallic solu- 
tions, the manufacture of plated wares began to advance; and so 
rapid has been its progress, that, at the present time, thousands 
of persons are employed in it, and electro-plate productions are 
used in all parts of the world. 
