. 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 . onnection is made between the zincand medal or mould by a bindingscrew; or by a mere contact, as inthe figure. 103. I must again dwell upon thephilosophy of the action of this ar-rangement, and return to
. 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 . onnection is made between the zincand medal or mould by a bindingscrew; or by a mere contact, as inthe figure. 103. I must again dwell upon thephilosophy of the action of this ar-rangement, and return to first princi-ples, in order to impress them more firmly on the mindsof those who read these pages with the intent to repeatthe experiments. For it is a matter of some importance,in employing the costly salts of the noble metals, to havethe principles of the experiment traced out as distinctlyas possible. 104. In the arrangement just described, the natureof the deposit will depend upon the principles elsewhere(§ 78) set forth; and, d fortiori, from the facility withwhich the salts of silver or gold are decomposed, therewill be a much greater chance of releasing hydrogen,and spoiling the experiment; to prevent which, there-fore, ample provision must be made. For instance, ifthe silver solution is weak in proportion to the energyof action between the zinc and acid water, the electricity. SOLUTIONS AND APPARATUS. 19 developed will be more than sufficient to release puremetal, and hydrogen will be evolved, the result being adeposition of oxide. Or, if the balance between thestrength of the solutions be duly adjusted, the relationbetween the size of the zinc and of the medal or mouldmay be such as to determine the same result. It istherefore requisite that the water which excites the zincshould contain very little acid—a few drops, more orless in proportion as the cyanide solution contains moreor less of the oxide; and that the strength of the lattershould be maintained by a fresh
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