A treatise on the theory of solution including the phenomena of electrolysis . t colours, and nearly equal specific re-sistances, were placed one over the other in avertical glass tube. In one case, for example,decinormal solutions of potassium carbonate andpotassium bichromate were used. The colourof the latter is due to the presence of the bi-chromate group, Cr207. When a current waspassed across the junction, the anions CO3 andCr207 travelled in the direction opposite to thatof the current, and their velocity could be de-termined by measuring the rate at which thecolour boundary moved. Simi
A treatise on the theory of solution including the phenomena of electrolysis . t colours, and nearly equal specific re-sistances, were placed one over the other in avertical glass tube. In one case, for example,decinormal solutions of potassium carbonate andpotassium bichromate were used. The colourof the latter is due to the presence of the bi-chromate group, Cr207. When a current waspassed across the junction, the anions CO3 andCr207 travelled in the direction opposite to thatof the current, and their velocity could be de-termined by measuring the rate at which thecolour boundary moved. Similar experimentswere made with alcoholic solutions of cobaltsalts, in which the mobility of the ions was found to be muchless than in water. The behaviour of agar jelly was theninvestigated, and the mobility of an ion was shown to be verylittle less in a solid jelly than in an ordinary liquid velocities could therefore be measured by tracing thechange in colour of an indicator or the formation of a pre-cipitate. Thus decinormal jelly solutions of barium chloride. 1 Physical Review, i. 51 (1893). 2 Phil. Tram. A, clxxxiv. 337 (1893); Phil. Mag. Oct. 1894 ; Phil. , CLxxxvi. 507 (1895). 218 SOLUTION AND ELECTROLYSIS [CH. IX and sodium chloride, the latter containing a trace of sodiumsulphate, were placed in contact. Under the influence of anelectromotive force, the barium ions moved up the tube, andtheir presence was shown by the trace of insoluble bariumsulphate formed. By keeping the conductivities of the twosolutions nearly the same, discontinuity of potential gradientwas avoided, and the gradient could then be calculated fromthe area of cross section of the tube, the conductivity of thesolution, and the strengtli of the current as measured in agalvanometer. In dilute aqueous solutions of simple salts, the direction ofmotion observed at the junctions was always normal; butas the concentration was increased, in some cases, such asthat of alcoholic cobalt solut
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