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Description: | L.C.E.98. (old departmental catalogue number in aluminium paint, removed). Liquid voltameter- there are four of these vessels ( typed on a paper label, removed) MANU unsigned. 19th century. DES after NICHOLSON,William. 1800 London, England. DES after CARLISLE,Antony,Sir. 1800 London, England. DES after FARADAY,Michael. 1834 The Royal Institution of Great Britain, 21, Albemarlle Street, London, England. This voltameter was used to measure a quantity of electricity by the decomposition of water or by the deposition of nickel. from a solution of one of its salts.
For the decomposition of water: as electricity passed throught the cell water was reduced to its component parts; hydrogen and oxygen and since these are gases they bubble off. The stopper was removed from the vessel and the vessell weighed empty and then with a quantity of wate acidified with sulphuric acid. The electricity was then passed through the cell via the nickel electrodes. After a recorded period of time the vessel was reweighed and the amount of water that had been decomposed noted.
Faraday's first law of electrolysis states that the mass of a substance liberated at an electrode is proportional to the quantity of electricity passing through the electrolyte. His second law states that a given quantity of electricity passing through the water will liberate an amount of of substance proportional to its chemical equivalent. The chemical equivalent of an element is equal to its atomic weight divided by its valency.
The mass of water decomposed by the p[assage of one amp second of electricity is equal to the electrochemical equivalent of hydrogen (0.00001044) times the atomic weight of water (16 + 2.016) divided by 2 = 0.0000936g therefore the current that has passed through the cell equals the wieght of water lost x 0.0000936 x the time in seconds.
When a solution of nickel salt was used the negative electrode was weighed to measure the weight of nickel deposited. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
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