516 Mr. W. C. M. Lewis : Experimental Examination 
these very uniform in size. The radius o£ a drop is taken 
as being -0000425 cm. The maximum value would be 
represented by 
r = -00005 cm., 
and as a minimum, 
r = -000035 cm. 
Substituting these values in the first determination with 
oil B, we obtain the following result : — 
r = -000035 cm., r = 4'4 x 10~ 6 grin, per cm. 2 
r = -000050 „ r = 6-9 x 10" 
r = -0000425 „ r = 5-9 x 10- 
JJ 
•5 
It is evident from these figures that the method is not 
sufficiently accurate to detect a different value of V cor- 
responding to solutions of strengths *317 and *2 per cent, 
respectively. The different values obtained are within the 
limits of experimental error. 
Comparison of Experimental values ofY with Calculated 
values. 
The calculated value for T is, as already pointed out, 
c da 
~RT Tc' 
Let us take as a example the second determination with 
oil B :— 
The concentration of the solution = c = -2 per cent. 
= •002 grin, per c. c. 
Temperature T = 289 abs. 
B is the gas constant. For one gram of solute, 
2 x 4-2 x 10 7 ergs 
R 
molecular weight 
The molecular weight determined as already described is 
140 in aqueous solution. 
The coefficient -=-, read from the curve fig. 3 at the point 
where c = 2 per cent., gave 
do- 9*5 dynes 
= 4750. 
dc -002 grm. per c. c. 
The true value of this probably lies between the limits 
4800-4700, i. <?., an error of about 2 per cent. 
