456 G. 0. Squier — Electro-Chemical 



gas bubbles only appeared in small quantities after a consider- 

 able time, further addition of small quantities of the dioxide 

 showed the " protective throw" to be very decided with sul- 

 phuric acid when the hydrogen is removed from the surface 

 of the electrodes in this maimer. 



G. The electromotive force. 



Several attempts were made to obtain the relation between 

 the strength of field and the electromotive force developed in 

 the " protective throw," but it was difficult to obtain consistent 

 readings owing to the trouble of balancing the original deflec- 

 tion, and the small absolute values of this electromotive force 

 when hardened gelatine was employed. 



A curve was constructed, however, showing the variation of 

 the galvanometer deflection with the strength of field, using 

 nitric acid solution without gelatine. This is sliown in fig. 2, 

 p. 449. 



The readings were taken one after another, as rapidly as 

 possible, to eliminate the damping effects of the iron salts 

 formed. 



The curve exhibits the general character of the variation. 

 In the region from about 3,500 H to 8,000 H the greatest rate 

 of change occurred, and beyond 10,000 H the curve became 

 nearly horizontal for the particular electrodes used. Curves 

 were also constructed for the " concentration throw " on mak- 

 ing the field under different conditions, and they were approxi- 

 mately right lines more or less inclined, according to the 

 amount of iron salts present. 



With the sulphuric acid solution already given, the electro- 

 motive force varied from - 0033 to 0'0078 of a volt, while with 

 the nitric acid solution it became as great as 0'036 of a volt. 

 In making all the solutions used with the different substances, 

 amounts were taken proportional to their particular molecular 

 weights, and then halved or doubled until of a suitable strength 

 to give results with the galvanometer. It was thought possible 

 at the beginning, that this might lead to some relations between 

 the protective results and the strengths of the particular solu- 

 tions, but the general irregular character of the whole phe- 

 nomenon prevented comparisons in this respect, and all that 

 can be stated is, that both the " protective throw " and the con- 

 centration effect, in general, increased rapidly with the strength 

 of the solution. 



H. Influence of a 'periodic magnetic field upon the cell. 



An experiment was made to determine the behavior of the 

 standard nitric acid cell when the magnetic field was made and 



