j Kohlenberg—Osmosis and Osmotic Pressure. 263 
to keep 1 the air in the laboratory entirely free from it. The 
effect appears to be cumulative in character, for one’s system 
seems to become more and moire sensitive to the substance. 
For this reason I felt constrained not to prolong the work with 
pyridine unduly. It will be remembered that I have carried 
on experiments with pyridine continuously for about two years, 
and off and on for a much longer time. During the investiga¬ 
tions I have at times found it necessary to counteract the de¬ 
pressing effects of pyridine by taking small doses of strychnine. 
The results of the experiments performed with the stirring 
apparatus will now be given. It need hardly be stated again 
that the LdCl and the sugar were dry and of a high degree of 
purity, as was also the pyridine. 
57) The inner liquid was 0.125 normal solution of LiCl in 
pyridine and the outer liquid pure pyridine. It required 46 cc. 
to fill the cell. The volume of the outer liquid was 600 cc. 
The temperature was 19.0,° and the experiment was run for 
three days with constant stirring. The maximum height which 
the mercury column reached was 51.2 cm. at 19.0° 0, corrected. 
This height was practically attained during the first 24 hours. 
At the end of the experiment, the whole of the outer liquid was 
evaporated to dryness and the LiCl in the residue estimated. 
It was found that the 600 cc. of outer liquid contained 0.0130 
grams of LiCl, which shows definitely to what extent the solute 
has actually passed into the outer liquid. 
In the light of what has been said in the precediug pages, it 
is evident that a determination of the exact amount of solute 
present in the outer liquid at the time when the maximum pres¬ 
sure is attained is an essential part of all final osmotic pres¬ 
sure measurements,, yet such estimations have hitherto always 
been omitted even in experiments in which great care has been 
bestowed upon other details. 
58) This experiment was exactly like the the preceding one 
(No. 57) except that the outer liquid consisted of 1200 cc. of 
pyridine instead of 600 cc. and the temperatures were as in¬ 
dicated below. The experiment was continued for 27 days, at 
the end of which time an examination showed the membrane 
