510 Mr. W. C. M. Lewis : Experimental Examination 
Variation of the Interfacial Tension with the Concentration 
of Sodium Glycocholate Solutions. 
First Series. — Oil A. 
Aqueous solutions of the sodium glycocholate were pre- 
pared of the following concentrations : — 
1% 0-8% 0-5 % 0-33 7. 0-25 7, 0-18% 0-125% 
0-1% 0-05% 0-01% 0-001%. 
On being freshly prepared, the aqueous solutions of these 
concentrations were quite transparent, but with considerable 
rapidity — 2 to 3 hours — in the case of the more dilute, a 
white turbidity manifested itself. All tension measurements 
were therefore made with fresh transparent solutions so that 
the values obtained might be quite comparable. 
The following table gives the results obtained with oil A. 
The first column gives the concentration of the solution ; the 
second, the corresponding drop-number ; the third gives the 
relative tension as deduced from the relation already obtained 
(pp. 507, 508), viz., that the drop-numbers are inversely as the 
tension ; the fourth column gives the absolute values of the 
tension based on the oil- water determination 33*6 dynes/cm. 
and by applying the values of column 3. 
Table II.— Oil A. 
Per cent. 
Drop- 
Relative 
Tension 
Concentration. 
number. 
Tension. 
dynes/cm. 

183 
1-000 
33-60 
o-ooi 
191 
0-958 
3220 
o-oi 
219 
0-836 
18 08 
0-05 
244 
0-750 
25-21 
01 
280 
0-654 
21-96 
0-125 
297 
0616 
2070 
0-18 
365 
0-501 
16-81 
025 
418 
0-438 
14-71 
0-33 
489 
0374 
12-57 
05 
536 
0-341 
11-48 
0-8 
558 
0-328 
1103 
10 
566 
0-323 
10-86 
The above values in columns one and four are plotted in 
fig. 2. It will be noticed how exceedingly marked is the 
lowering effect of the sodium glycocholate upon the inter- 
facial tension. 
We are therefore, now, in a position to obtain an experi- 
