To use all functions of this page, please activate cookies in your browser.
With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
- My watch list
- My saved searches
- My saved topics
- My newsletter
The Clark cell, invented by English engineer Josiah Latimer Clark in 1873, is a wet-chemical cell (colloquially: battery) that produces a highly stable voltage usable as a laboratory standard.
Additional recommended knowledge
Clark's original cell was set up in a glass jar in a similar way to a gravity Daniell cell. The copper cathode was replaced by a pool of mercury at the bottom of the jar. Above this was the mercurous sulphate paste and, above that, the zinc sulphate solution. A short zinc rod dipped into the zinc sulphate solution. The zinc rod was supported by a cork with two holes - one for the zinc rod and the other for a glass tube reaching to the bottom of the cell. A platinum wire, fused into the glass tube, made contact with the mercury pool. When complete, the cell was sealed with a layer of marine glue.
The H-form cell was introduced by Lord Rayleigh in 1882. It was set up in an H-shaped glass vessel with zinc amalgam in one leg and pure mercury, surmounted by a layer of mercurous sulphate paste, in the other. The vessel was filled, nearly to the top, with zinc sulphate solution. Electrical connections to the zinc amalgam and the mercury were made by platinum wires fused through the lower ends of the legs.
The design had two drawbacks - a rather large temperature coefficient of -1.15 mV/°C, and corrosion problems caused by the platinum wires alloying with the zinc amalgam connections where they enter the glass envelope.
Clark cells were later made obsolete by the more temperature-independent Weston cell design.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Clark_cell". A list of authors is available in Wikipedia.|