Viscosity of a Solution of Saponine. 



411 



size; and as those called " large " are much larger than those 

 actually used in the experiments, the correction which might 

 otherwise have been necessary has been neglected. 



The following are the results of the experiments on saponine 

 solution : — 



Position of plate. Upper 

 surface 



Time of oscillation. 



Log. decrement. 



•14 millim. above liquid... 



9*51 sec. 

 9-50 „ 

 9-55 „ 

 9-60 „ 

 963 „ 

 9-58 „ 

 9-55 „ 

 9-62 „ 

 9-63 „ 

 9-62 „ 

 959 „ 



•1960 

 •2520 

 •0067 

 •0045 

 •0039 

 •0034 

 •0030 

 0025 

 •0022 

 •0020 

 •0019 





•2 



•3 



•4 



•6 



1-0 



1-4 



2-4 



3-65 





These results are shown on the accompanying curve (p. 412). 



With regard to the first two observations, in which the plate 

 was oscillating in the surface of the liquid, only two complete 

 oscillations were obtainable for each determination ; and as 

 the logarithmic decrement was found to diminish considerably 

 as the amplitude increased, a number of observations at dif- 

 ferent amplitudes were taken. These were plotted down in 

 the form of a curve, showing the amplitudes and logarithmic 

 decrement; and from these curves the logarithmic decrement 

 for an arbitrary standard initial amplitude of 500 divisions 

 was taken. The slope of these curves was so considerable that 

 our observations can only be considered as giving an inferior 

 limit to the resistance of the surface of the saponine solution. 

 When the plate was once immersed below the surface, it was 

 found that twenty or more oscillations were readily obtained, 

 and that the magnitude of the original amplitude had little 

 or no effect. The variations of temperature were small (the 

 difference being only o, 7 C); and as their effect on the surface- 

 viscosity is unknown, no correction was made for them. The 

 error thus introduced would, however, as the regularity of the 

 curve shows, be small. 



These observations, then, enable us to compare the resistance 

 offered to a disk when oscilating in, or just below, the surface 

 of a saponine solution and of water. 



Thus we get for the surface of saponine, 



MX _ 186653 x -252 

 T ~ 9-5 



4951; 



