374 Mr. H. A. McTaggart on 



from Traube (Journ. de Chim. et Pliys. iii. p. 587, 1905) 

 and Freundlich (Kapillarch.. p. 64). Tbe curves showing 

 the effect of concentration on tbe velocity, i. <?., on the 

 electric charge occur in the same order as in the case 

 of surface tension. The alcohol which lowers the surface 

 tension most rapidly also reduces the electric charge most 

 quickly. 



The pure alcohols themselves showed no cataphoresis of 

 air-bubbles. This was not expected, particularly for methyl 

 alcohol, because Baudouin (C. It. cxxxviii. pp. 893, 11C>5) 

 found for it a small but easily measurable electric osmosis 

 through certain porous diaphragms — the sign, however, 

 depending on the nature of the diaphragm. Besides this, 

 methyl and ethyl alcohols give rise to electrification in water- 

 fall and in bubbling experiments, which might lead one to 

 expect some effect. 



In methyl alcohol, bubbles of air of a size *10 mm. showed 

 no sign of motion under potentials of 100 volts/cm. The 

 application of the potential in this case had the curious 

 effect of hastening the absorption of the bubble. 



In ethyl alcohol 125 volts/cm. gave no motion to an air- 

 bubble, not even in a 50 per cent, aqueous solution. 



In a 25 per cent, solution of propyl alcohol no motion 

 can be observed with 125 volts/cm. for air-bubbles artificially 

 made. 



In isobutyl alcohol no motion of an air-bubble is 

 apparent. 



It does not follow, of course, that a cataphoresis of other 

 particles than air-bubbles does not occur in these alcohols, as 

 the case of benzine spheres in 25 per cent, propyl alcohol 

 shows as well as Baudouin's experiments. 



The results for the first four fatty acids are given here. 

 The concentrations are necessarily small for the reason ex- 

 plained in the last paper. A complete series of observations 

 for formic acid is given to show again the effect of size, these 

 acids being adsorbed like the alcohols and being very active 

 in reducing the surface tension. The concentrations are 

 given in ccs. of acid per c.c. of water. 



The readings are not as regular as they should be — perhaps 

 because of some unavoidable impurity introduced with the 

 bubble by the pipette, or perhaps — where the final reading 

 for a bubble is large — because of some residue left by the 

 acid in the surface. 



