1865.] 



Prof. Guthrie on Bubbles. 



31 



So that if the surface of the original bubble be 1, the surface of the 

 two bubbles of half the size taken together is 1-259885. By making the 

 gas-delivery-tube small, the absorbent surface of the same quantity of gas 

 which passes through is increased in this manner, and the absorption is 

 consequently more rapid or more complete. 



Effect of change in the chemical nature of the liquid medium. To 

 examine this (perhaps the most interesting phase of the causes of variation 

 in bubble-size), the gas-bag L was replaced by a chloride-of-calcium tube. 

 The cotton-wool of J was saturated with the liquid, which was placed for 

 examination in G ; so that the bubbling gas was dry air already saturated 

 with the vapour of the liquid through which it had to bubble. It is clear 

 that if the air so charged were to come into contact with the water in A, 

 the vapour would dissolve in the water, while the air would become moist ; 

 a difference in volume would be thereby occasioned, according to the dif- 

 ference of tension of the vapour of the liquid in G and J and that of 

 water. To avoid this source of error, the vessel A was filled with mercury. 

 After each experiment the vessel A was completely refilled with mercury, 

 so as to expel the vapour of the liquid employed in the previous experi- 

 ment. The mercury was then run off at D, until it fell in A nearly to the 

 mark a. The liquid under examination in G had a height above h in- 

 versely as its specific gravity : this the graduation of the tube G made 

 easy. By this means the pressure on the gas as it issued from h was the 

 same in all the experiments. The vessels A, G, and J were all sunk in the 

 same trough of water, so that the volume of the air should undergo no 

 alteration from temperature, either during or after its passage through G. 

 When gt had been brought exactly to 2", and the mercury in A had sunk 

 to a, a graduated burette was brought under the end of the siphon D, 

 and kept there while 100 bubbles passed through G. The numbers of 

 column 2 are each of them the mean of two determinations. 



TABLE e. 



ff t=2". 



T=25 C. 



B = 764 millims. 



