The theory and practice of electrolytic methods of analysis / by Dr. Bernhard Neumann ; translated by John B.C. Kershaw, F.I.C.
- Neumann, Bernhard, 1867-
- Date:
- 1898
Licence: Public Domain Mark
Credit: The theory and practice of electrolytic methods of analysis / by Dr. Bernhard Neumann ; translated by John B.C. Kershaw, F.I.C. Source: Wellcome Collection.
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![is formed after some time, when the solution used is very- dilute. According to Hittorf, the potassium ion migrates to- wards the kathode and there decomposes water with libera- tion of hydrogen : K4 + 4H20=4KOH+H4. The radical Fe(CN)6 drifts towards the anode, and in concentrated solutions—that is to say, in solutions contain- ing sufficient potassium ferrocyanide—forms potassium ferricyanide : 3K4Fe(CN)6 + Fe(CN)6=4K3Fe(CN)6. When, however, the solution is very dilute, the reaction takes a different course, and Prussian blue is formed according to the following equation : Fe(CN)6 + 2H20=H4Fe(CN)G + 02 7H4Fe(CFT)6 + 02=24HCN + (Fe2)2[Fe(CN)c]3 + 2H20 When the anions are constituted of many elements, especially in the case of the radical groups of organic acids, one can frequently observe that reactions occur between the similarly constituted anions. These reactions result generally in the formation of gaseous products, which either escape or enter again into combination with other ions—simple or complex—present in the solution. Such reactions occur during the electrolysis of nearly all organic acids and salts. The decomposition of formic acid by electrolysis takes place according to the following equations : HCOOH=H + HCOO HCOO + HCOO=H2 + 2C02 2HCOO + H20 = 2HC00H + O At the anode, carbon dioxide and oxygen are evolved, while hydrogen is evolved at the kathode. When the alkali salts of this acid are electrolysed, hydrogen is also evolved at the kathode in consequence of the reaction between the liberated alkali metal and the water. When](https://iiif.wellcomecollection.org/image/b28121284_0027.jp2/full/800%2C/0/default.jpg)
