30 



Prof. Guthrie on Bubbles. 



[Jan. 19, 



into the cork of the tube G, fig. A. The vessel M was a burette graduated 

 into tenths of cubic centimetres. A hundred bubbles at gt=2"-Q were 

 allowed to pass through G, and the water from D was measured. 



TABLE S. 



From this Table we see that the bubble-size is very sensitive to the 

 size of the orifice. The bubble-size is doubled if the radius of the orifice 

 is increased fivefold ; and so on. The same effect can also be well shown 

 in a manner quite analogous to that adopted * to show the effect of varia- 

 tion in radius of curvature of the solid (SLG). 



If the same quantity of gas be made to bubble in succession through the 

 same liquid, similarly disposed in similar vessels, and if the tubes through 

 which it is delivered have continually decreasing diameters, then the rates 

 of bubbling are seen to follow the inverse order of the diameters of the 

 tubes. Fig. D shows such an arrangement, which requires no explana- 

 tion. In fact the reason why increase in radius of curvature in the case 

 SLG produces increase of drop-size is very similar to that which causes 

 increase of orifice to increase bubble-size in the case SGL. In the 

 former case the thickness and general approximation of the residual liquid- 

 film to the drop is greatest in large and flat surfaces ; in the latter the 

 area of residual gas is larger when the orifice is larger. When, around a 

 large orifice, the liquid medium closes upon the bubble, the latter is not so 

 straitened for material as when the orifice is narrow. 



The influence of the size of the tube upon bubble-size is of considerable 

 practical importance. In washing a gas, in separating two gases from 

 one another by a medium which absorbs one of them, in saturating a 

 liquid by a gas (a process which so often occurs in manufactures and 

 analysis), the completeness of the operation invariably depends upon the 

 extent of surface in common between the gas and liquid during a given 

 time. If a spherical bubble, having the volume V and the surface S, be 



V 

 divided into two equal spherical bubbles, each having the volume -^ and 



the surface s, then S 1 



On Drops, p. 460. 



