28 



Prof. Guthrie on Bubbles. 



[Jan. 19, 



The reason why bubbles are less sensitive to variations in gt than are 

 drops is sufficiently obvious. In the case of SLG, variation in gt affects 

 the size of a drop by varying the thickness of the liquid-film which covers 

 the solid at the moment of the drop's separation. We have seen that 

 when this film is thin, in consequence of slowness in the supply of liquid to 

 the solid, the size of the drop is diminished, because the solid reclaims 

 liquid from the drop-root at the instant of the latter' s departure. But in 

 the case of a bubble, at least in the arrangement of the above experiments, 

 there is in all cases an indefinitely great aeriform residue, the separation 

 of the bubble being determined by the superior density of the liquid medium, 

 and by its persistent cohesion. 



Rate being thus of no appreciable influence upon bubble-size, we are not 

 compelled to take the same extreme precaution to ensure uniformity of gt, 

 as was found necessary with drops. 



Effect of change in the chemical nature of the bubble-gas. The gases 

 examined were hydrogen, oxygen, nitrogen, carbonic acid, and atmospheric 

 ah-. Boiled water was left for several hours in the bags containing the 

 gases, so that the gases might be perfectly saturated with water, and the 

 water with the gases, and so that they might have the same temperature. 

 This water was then employed to fill the vessel A. By this means all 

 disagreement between the volume of the bubbles and the volume of the 

 water flowing from D, caused by the solution of the gas in the water of A, 

 is avoided. In each case the gas was allowed to bubble through G until 

 the water in it was saturated. 



The following Table shows the results obtained : 



Column 1. The gas employed. 



Column 2. The number of bubbles having together the volume 50 cub. 

 centims., each number being the mean of three experiments. 



Column 3. The absolute mean volume of a single bubble. 



TABLE y. 

 M=50 cub. centims. 



T=24C. 

 B=766 millims. 



