✨ Technical Description
2172
THE NEW ZEALAND GAZETTE.
[No. 80
80
the UK form of Daniell’s battery. Inside this jar is placed a porous pot. The zinc is placed in the porous pot; and the negative plate, which is of carbon, is placed in the outer jar. The zinc is cast on to a stout copper wire, and both are well amalgamated.
Each plate is surmounted by a terminal, and any number of cells may be connected together in series.
In the outer jar are placed 3 oz. of bichromate of potash and 4 oz. (measures are supplied for this purpose) of sulphuric acid.
In the porous pot are placed 2 oz. or two measures of mercury. Both the porous pot and the outer jar are then filled up to within 2 in. of the top with water. As the mixing of water with sulphuric acid produces great heat—sufficient, in fact, to fracture a glass jar—a better plan than placing first the sulphuric acid and then the water in the jar is to prepare a solution of sulphuric acid in an earthen vessel, and to pour this solution into the jar. The strength used is about one part sulphuric acid to nine parts water. The acid is placed in the earthen vessel first and the water then poured in; sulphuric acid should never be poured into water.
The zinc and its copper rod are then amalgamated afresh by dipping it into mercury covered with diluted sulphuric acid, and rubbing the mercury over the metals until they are quite bright. The terminals and contacts between the different cells are then made bright and clean. The battery will soon be ready for work.
The sulphuric acid passes into the zinc cell when the plates are connected, attacks the zinc, and forms sulphate of zinc, while the hydrogen reduces the bichromate of potash to a lower form called the dichromate. The mercury keeps the zinc perfectly amalgamated, so that no local action takes place. There is secondary action in the battery when the solutions become saturated, which results in the formation of beautiful dark-violet crystals of “chrome-alum” on the carbon plate. This is a double salt, a sulphate of chromium and potassium.
The secondary action just referred to is only to be prevented by the occasional withdrawal of some of the liquid, and its replacement by fresh sulphuric acid and water, an operation which should be performed immediately the deposition of crystals is detected. The crystals themselves should of course be removed.
As long as the bichromate-solution remains an orange colour little need be done; but, if it turns blue, fresh bichromate
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NZ Gazette 1905, No 80
✨ LLM interpretation of page content
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Description of Bichromate Battery Construction
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🏗️ Infrastructure & Public WorksBichromate battery, porous pot, zinc plate, carbon plate, sulphuric acid, bichromate of potash, mercury, chrome-alum, battery maintenance, electrical cells