518 Mr. W. C. M. Lewis : Experimental Examination 
into the lower part of the tube. When A is empty, the 
tube B (which has a rubber joint near the top) is nipped at 
this point and the upper portion disconnected. The lower 
solution (which is 250 c.c. in volume) is run off from below, 
and a drop-number through it taken with the pipette. The 
fall in concentration is read off by means of fig. 3 — or, 
rather, a somewhat enlarged form of fig. 3 ; the enlargement 
being necessary for accurate readings on account of the 
very small changes in concentration produced by this method, 
the fewer large drops offering a very much smaller surface 
than the emulsion particles. 
Example : Oil B. 
One litre of '25 per cent. sod. glycocholate was prepared. 
The solution w r as poured into B and C as described, and after 
the drops have been passing for about 2 hours the reservoir A 
was empty and the contents of tube B run off. Through this 
solution a drop-number gave 466, i. e., a tension of 13*2 dynes, 
corresponding on the curve to a concentration '243 per cent. 
Hence the fall in concentration = *00 7 per cent. 
.*. for 250 c.c. (the volume of B) the total quantity 
removed ='0175 grm. 
The volume of the oil-reservoir =168 c.c. 
The time of formation of 50 drops was taken at the 
beginning, in the middle, and near the end of the expe- 
riment. It was found that the middle value was the mean 
of the beginning and end, viz. 50 drops in 40 seconds. 
Total time of emptying A . . = 7940 sees. 
.'. total number of drops . . =9925. 
Hence volume of a drop . . = *0169 c.c. 
.*. radius of a drop = "160 cm. 
and hence total adsorbing area = 3192 cm. 2 
.*. Adsorption coefficient = 5'4 x 10~ 6 gram per cm. 2 
A second determination was made in which three times 
the former quantity of oil was used, and hence a greater 
fall in concentration was observed, which is in favour of a 
more trustworthy result : — 
Total volume of oil used . . = 504 c.c. 
Total time of dropping . . =20520 sees. 
Total adsorbing area . . . = 7414 cm. 2 
Total mass adsorbed = "022 grm. 
.*. Adsorption coefficient = 3*1 x 10~ 6 . 
