Effects due to Magnetization. 455 



Applying this fact to the exposed conical point electrode, 

 we see that local electric currents exist from its vertex to the 

 other parts of the surface, returning by way of the metal. 

 In the case of the vertical rod, these currents pass from the 

 poles at its ends, through the liquid, to the neutral portions, 

 returning as before. 



These currents* under the influence of the poles themselves, 

 would cause electromagnetic rotations of the liquid, as we find 

 them. The mere mechanical influence of these rotations, as 

 in the case when the liquid is artificially stirred, is to increase 

 the chemical action upon the point, causing it to tend to act 

 more like a zinc. 



F. Acids %ohich attack iron with the evolution of Hydrogen. 



Professor Bowland had observed the "protective throw" 

 with such acids to be extremely small and difficult to detect, 

 except by very sensitive apparatus. The sensitive galvanom- 

 eter was set up, and every precaution taken against inductive 

 effects. A telescope and scale were used in this part of the 

 work. 



Several substances were first examined, among them being 

 hydrochloric acid, acetic acid, perchloric acid, chlorine water, 

 copper sulphate, ferric chloride, sulphuric acid, etc., but as 

 these observations added nothing to the results already ob- 

 tained, they are not given here. 



After several trials a standard sulphuric acid solution was 

 made up as follows : 



Distilled water . 10 grams 



Gelatine .. 1 gram 



C. P. Sulph. acid (sp. gravity 1-826).. .1-062 grams 



More strongly acidulated gelatine would not harden, and 

 weaker solutions gave too small effects. 



The " protective throw " was detected, but the point very 

 soon became completely covered with minute bubbles of 

 hydrogen, so that the electrodes had to be cleaned constantly. 



The effect of adding hydrogen dioxide to the solution was 

 next tried, since this would facilitate the removal of the hydro- 

 gen as soon as formed,f which was thought to act merely 

 mechanically. 



When about l cc of H 2 2 was added to the solution, the 

 " protective throw " became much more prominent, and the 



* The rotations produced in liquids by axial currents, e. g. currents coinciding 

 with the direction of the magnetic lines of force as distinct from radial currents, 

 have been studied by Dr. Gore, Proceedings of the Royal Society, xxxiii, p. 151. 



f J. M. Weeren, Berichte der Deutschen Chemischen Gesellschaft, No. 11, 1891. 



