1893.] Gravity of Fluid Bubbles through Liquids. 



19 



In the following table are shown the observed and calculated 

 " times " in the case of two sized tubes. The first column gives the 

 approximate percentage composition of each solution, beginning with 

 glycerine and ending with pure water. The fourth column consists 

 of the ascertained viscosity in terms of that of water. Columns 5 

 and 6 are 1^he calculated and observed " times of descent " respec- 

 tively for a tube of diameter 0*655. Columns 7 and 8 are the like for 

 a tube of diameter 0'895. Temperature between 10 12. 



Table VII. Chloroform Solutions of Glycerine and Water. 



It will be seen from this table that within certain limits we are 

 justified in assuming the velocity to be inversely as the viscosity, but 

 there is a complete failure in the applicability of the law in cases 

 where the viscosity is small. The retardation observed in such cases 

 is doubtless due to the formation of eddying motions in the fluid, and, 

 indeed, if any small motes which happen to be present be watched, 

 considerable commotions are always to be seen as the bubble passes 

 whenever there is this retardation. 



The retardation is even more marked in the case of air bubbles, for 

 as will be seen from the following table, not only are the observed 

 values greater than the calculated values, but they are actually greater 

 than values observed with greater viscosities, i.e., than those given 

 higher up the list. Diameter of tube = 0*665 c.c. 



This retardation is better shown in Diagram 2, which is plotted 

 from a number of careful observations. The maximum velocity with 

 this sized tube corresponds to about 33 per cent, of glycerine, the 

 velocity of which is about three times that of water at the tempera- 

 ture of the experiments. The abscissae represent the percentage com- 

 position of the solutions, beginning on the left with glycerine. The 

 ordinates are the corresponding velocities. 



* The values of surface tension printed in italics were interpolated. 



c 2 



