486 Lieut. G. 0. Squier on the Electrochemical 



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, which experiment confirms. 



F. Acids which attack Iron with the Evolution of Hydrogen. 



Professor Rowland had observed the " protective throw " 

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

 except by very sensitive apparatus. The sensitive galvano- 

 meter 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, &c, but as 

 these observations added nothing to the results already 

 obtained they are not given here. 



After several trials a standard sulphuric-acid solution was 

 made up as follows : — 



Distilled water 10 grammes. 



Gelatine 1 gramme. 



C.P. Sulphuric acid, sp. gr. 1*826 ... 1*062 gramme. 



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 

 hydrogen as soon as formed f, which was thought to act 

 merely mechanically. 



When about 1 cubic centim. of H 2 2 was added to the 

 solution the "protective throw" became much more promi- 

 nent, and the gas bubbles only appeared in small quantities 

 after a considerable time. Further addition of small quantities 



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

 coinciding with the direction of the magnetic lines of force as distinct 

 frorn radial currents, have been studied by Dr. Gore (Proceedings of the 

 Royal Society, xxxiii. p. 151). 



t J. M. Weeren, Berichte der Deutschen Chemischen Gesellschaft, 

 No. 11 (1891). 



