On the fragments of the ore which extend up outside of the electrolytic
bath is laid a plate of copper connected with the positive wire. Care
must be taken that this plate does not plunge into the bath, otherwise
the current would not traverse the ore at all. The cathode is preferably
formed of the same metal which is to be obtained. The bath should
not contain organic acids. In practice the common mineral acids are
employed, or their salts, selecting by preference a salt of the metal
which is to be isolated. It is convenient to pass the current through
the greatest possible number of small decomposition troughs, taking care
that the resistance in each is not too great. With a current of one and
the same intensity we obtain in n troughs n times as much metal as in a
single one. To keep down the resistance of the circuit we employ poles
of a large surface, i.e., plenty of ore and baths which are as good
conductors as possible.
The state in which the metal is deposited at the negative pole depends
on the secondary actions undergone by the electrolyte, and especially of
the escape of gas.
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