THE REACTION BETWEEN HYDROCHLORIC ACID AND POTASSIUM PERMANGANATE
Journal of the American Chemical Society
~YDROCHLORIC ACID AND POTASSDJM PERMANGANAYE~ 133 'These results show that the liquid junction formed by the confluence of the 2 streams gives exactly the same and just as constant a potential as does the one-way Bow of a single electrolyte. However, the stirred junctions formed here were not constant and in general gave lower potentials than the flowing junctions, whereas in the previous arrangement higher results were obtained. Summary. The above experiments have shown : I. That liquid
... That liquid junctions formed between the bearing surfaces of ground glass stoppers, in gelatin diaphragms and in parchment paper diaphragms, with 0 , I N hydrogen chloride and potassium chloride solutions are not constant and reproducible to closer than 0.2 or 0.4 of a millivolt . . That parchment diaphragms with stirring give somewhat more constant results. 3. That fresh junctions in tubes of 5 mm. bore give potentials reproducible in 0 . I N solutions to about *0.03-0.06 millivolt when oscillations of the electrolyte are prevented, but that with N solutions variations of * Q . 3 millivolt occur. 4. That stirred junctions sometimes give very constant potentials, but these are quite different from that produced by a "flowing" junction and, moreover, they differ, depending on the mode of stirring, etc. 5. That a "flowing" junction, obtained simply by having an upward current of the heavier electrolyte meet a downward current of the lighter electrolyte in a vertical tube at its point of union with a horizontal outflow tube, or by allowing the lighter electrolyte to flow constantly into a large volume of the heavier electrolyte, even with N solutions, gives potentials constant and reproducible to *O.OI of a millivolt. %'ASHINGTOI'I, D. c. On account of its convenience and ease of regulation, the reaction between hydrochloric acid and potassium permanganate has become the usual one for the preparation of chlorine for laboratory purposes. On looking over the text-books one finds some confusion of thought, some misstatements, and a certain amount of evasion of the facts involved The equation given for this reaction in most of the text-books is 2KMn04 + 16Hc1 -+ 2KC1 + 2MnCl2 + 8H20 f gC12.