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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    — 43 — quires assiduous care, and measurement. The approximate amount of metal, the amount of acid or alkali and the amount of water onght to be known. Moreover various media are con- veniently present. Dilute sulphuric acid is a very convenient medium from which to electrolyse salts of copper. Lead sepa- rates well upon the anode from solutions containing free nitric acid. The various organic acids have been very widely and suc- cessfully employed, a fact in relation with the peculiar electro- lytic behaviour of salts of organic acids already referred to. Acetic acid, citric acid, tartaric acid and oxalic acid have been most made use of. Very often it is best to use a saturated so- lution of ammonic oxalate. On adding this reagent to the metallic compounds a precipitate forms which redissolves in excess. The resulting liquid is submitted to electrolysis. Pyrophosphate of Sodium does not appear to yield such good results as the Oxalate of Ammonia at all events in the case of Zinc and Nickel. A saturated solution is added to the solution containing the metal until the precipitate first formed is redissolved. Farther additions of ammonia or ammonic car- bonate are recommended. The termination of the reaction may be inferred by using the ordinary qualitative reagents for the several metals. A drop is taken from the liquid upon white bibulous paper and the reagent applied. Where a beaker is used, and the liquid possesses highly distinctive colour the conclusion of the electolysis is very evident. It remains to be seen whether, when the liquids are not highly coloured, an index may not remain in the solution throughout; for example sulphocyanide of potassium in solutions of ferric salts. A simple method for reaching the same end, and involving no loss of fluid consists in exposing a fresh surface of plati- num, for example by tilting the platinum basin, to the fluid being electrolysed. If at. ihe end of half-an-hour or so no fresh metal has been thrown down it may be concluded that the reaction is at an end.