. Electrotype manipulation : Being the theory and plain instructions in the art of working in metals, by precipitating them from their solutions, through the agency of galvanic or voltaic electricity. Also in the arts of electro-plating, electro-gilding, and electro-etching; with an account of the mode of depositing metallic oxides, and of the several applications of electrotype in the arts . nd thesolution is decomposed by the use of a platinum terminalin connection with the copper of the battery, and thesubstance to be platinized in connection with the zinc,A few minutes action will suffice.
. Electrotype manipulation : Being the theory and plain instructions in the art of working in metals, by precipitating them from their solutions, through the agency of galvanic or voltaic electricity. Also in the arts of electro-plating, electro-gilding, and electro-etching; with an account of the mode of depositing metallic oxides, and of the several applications of electrotype in the arts . nd thesolution is decomposed by the use of a platinum terminalin connection with the copper of the battery, and thesubstance to be platinized in connection with the zinc,A few minutes action will suffice. Platinum is some- 56 ELECTROTYPE MANIPULATION. times platinized; but, for all practical purposes, silveris equally serviceable. This aggregation of small pointsfacilitates the liberation of the evolved hydrogen, whichescapes with a loud hissing noise, in place of adheringto the metal and interrupting the action. The arrange-ment is generally made with one platinized silver platebetween two zinc plates, as in the following figure, wheres is the silver plate connected with the copper of theusual decomposition cell, and z the zinc plate connectedwith the moulds. In employing this arrangement, caremust be taken to avoid dropping any sulphate of copperinto the acid water; for the copper would at once bereduced upon the silver plate, and by altering the natureof the battery would spoil 66. As the silver plate in this arrangement is betweenthe zinc plates, it follows that the streams of hydrogenmust ascend between the metals of the pair, so that,while in one sense they form a partial screen betweenthe plates, they, on the other hand, prevent the plates VOLTAIC APPARATUS TO BE USED. 57 being approximated within certain limits. A very in-genious modification of this arrangement has beendevised by Professor Grove,* who substitutes platinizedsilver gauze in place of the plate of silver ; as, by thismeans, a facility is afforded to the hydrogen of passingthrough the apertures of the
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