484 Lieut. Gr. 0. Squier on the Electrochemical 



D. The Iron Salts about the Point Electrode. 





The effect of artificially stirring the liquid, and the direct 

 influence of the fluid condition of the solution on the de- 

 flexions observed, at once suggested movements of the liquid, 

 produced indirectly by the magnet. In order to locate these 

 currents and determine their potence, a small cell was made 

 of two rectangular pieces of glass held by stout rubber bands 

 to thick rubber sides. Perforations in the sides admitted the 

 electrodes, which were point and disk as before. The cell, 

 between the poles of the electromagnet, was in a strong light, 

 and the movements in the liquid were easily perceptible from 

 the displacements of suspended particles introduced for the 

 purpose. When very dilute nitric acid was placed in the cell 

 and the magnet excited, some interesting phenomena were 

 observed. 



The liquid, at first colourless, almost immediately assumed 

 a pale brown colour about the point, but nothing appeared at 

 the disk electrode. The iron salts were drawn as soon as 

 formed towards the point electrode, since here the rate of 

 Variation of the square of the magnetic force is a maximum. 



As more iron was dissolved, a surface approximating to an 

 equipotential surface of the pointed pole, and enveloping the 

 coloured iron salts, was observed enclosing the point and at 

 some distance from it. The outline of the surface became 

 darker in a short time, and finally two or more dark contours, 

 separated by lighter portions and symmetrical with the outer 

 one, appeared between it and the point, indicating maxima 

 and minima of density. When the magnetic field was gra- 

 dually increased, this surface usually enlarged without breaking 

 up and holding the iron salts within it. On further strength- 

 ening the magnetic field to about 16,000 H, the ridges merged 

 into one thick black envelope around the point. 



This phenomenon is best studied with but little iron salts 

 present, and by watching the point electrode with a micro- 

 scope while the strength of the magnetic field is increased 

 and decreased continuously. The sections (fig. 3) show the 

 general form of these contours with different strengths of 

 field. 



Upon breaking the field everything dropped from the point 

 suddenly to the bottom of the cell, and on making the field 

 again it required a few seconds for the salts to reappear at the 

 point. 



This, at least partially, accounted for the sudden effects 

 often noticed at breaking the field circuit, and the compara- 



