The uses of electrolysis in quantitative chemical analysis / by J. Wilkie.

  • Wilkie, J.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: The uses of electrolysis in quantitative chemical analysis / by J. Wilkie. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    In using a platinum basin as one pole for the separation of iron and manganese it is convenient to make it the anode, and to replace the wire spiral by a more snitable apparatus by way of kathode. The spiral has been recommended, but it is not to he employed. A wider surface holding the Iron better ought to he used. This may consist of a platinum cylinder, a platinum cone or a platinum plate. The latter form laid flat under the surface of the solution is excellent; for it offers a wide surface, and opposes the carrying away of deposited metal by currents of gas. The metal employed for the electrodes is accordingly in most instances platinum, which must be scrupulously clean and of an even surface. It is well to wash with strong hydrochloric, and fuming nitric acid at inter- vales ; then with distilled water; and finally with ether. To prevent destruction of the metal for at times alloys form con- taining platinum and the metal deposited such as Zinc or Iron, it is desirable to overlay the platinum surface with a thin sur- face of Copper or of Silver. This is indispensably necessary in separation of Zinc and Nickel by volatilizing the former from a mixture containing the two metals. An alloy of platinum- zinc forms which does not. dissolve out in the strongest acids, with difficulty after melting with sulphide of potassium, and requiring in the end the use of sand. When the metal has been separated upon the surface of the platinum basin, the latter is washed out with distilled water, the washings being of course added to the original remnant of solution when other elements remain to separate—and then with absolute alcohol and then dried in the airbath at about lOOo c. Where the metal has deposited well these opera- tions do not take 10 minutes in all. There is an advantage here in employing a plate or cone of moderate dimensions as the kathode: it is small in size, and easy of weighing; in washing it only requires dipping into, and stirring round first in distilled water, then in ab- solute alcohol, to become adequately washed; and in the rare