220 J. A. POLLOCK. 



larger class than those in the acetic acid solution whose 

 origin has just been considered. 



The larger of the bubbles of the class now under discus- 

 sion are created by the partition of the volume of gas 

 entering the liquid, considerable portions of the gas being 

 4 pinched off,' as it were, by the action of currents in the 

 liquid, or, having lost their downward momentum, becoming 

 separated from the mass of inrushing gas owing to their 

 buoyancy. Bubbles made in some such way are always 

 created when a liquid of any kind is agitated, and the 

 class includes the largest of the bubbles which are produced 

 by any method of disturbance. 



But there are other bubbles of the same general class, 

 though much smaller, whose development follows a more 

 orderly course. These are shown in various stages of their 

 growth in the photographs of Plate X, the reference being 

 to bubbles from about a tenth to a few millimetres in 

 diameter in many cases still attached to the parent 

 surfaces. 



Figure 6, Plate X, shows clearly two of the bubbles in an 

 early stage of development, still part of the lower surface 

 of the bubble caused by a jet of carbonic acid entering an 

 0*1 per cent, aqueous solution of acetic acid, the pressure 

 of the gas being too low to cause the disintegration of 

 the surface of the main bubble. Figure 7 is a photograph 

 of a bubble of carbonic acid being formed in water, and 

 figure 8 one of a bubble of the same gas in a 0*1 per cent, 

 aqueous solution of sulphuric acid. 



Whatmough 1 shows that dilute aqueous solutions of 

 sulphuric acid have a surface tension which increases as 

 the concentration becomes greater, they may be said, then, 

 to lack the frothing property even more than water. The 



1 Whatmough, loc. cit. 



