58 Stiles and J 0rgensen. — Studies in Permeability . IV. 
In experiments with distilled water and low concentrations of sub- 
stances, which are continued over a considerable time, a complication is 
introduced by secondary reactions, such as the effect of substances produced 
by bacterial action in the medium. We have therefore in these cases also 
employed another method in which the liquid is constantly renewed, 
whereby such secondary reactions are eliminated. But during the first 
twenty-four hours the two methods give practically identical results with 
the material we have employed. We may therefore postpone the descrip- 
tion of this method until a later occasion. 
Experimental Results. 
In all experiments recorded in this section twenty discs of potato, 
weighing altogether about 9 grm., were kept in 50 c.c. of solution at 20 ° C., 
at which temperature also the conductivity measurements were made. 
The experiments were generally continued for 34 hours, but in some cases, 
of which mention will be made, the time of experimentation was consider- 
ably longer. The conductivity measurements were all corrected for 
depression in their value caused by the presence of non-electrolytes in the 
external solution in the manner described in the previous section of this 
paper. The conductivities are stated in arbitrary units. To obtain the 
actual specific conductivities the values given have to be multiplied by 
a constant. 
When exosmosis is complete and equilibrium established between the 
electrolytes in the external solution and inside the plant cells, the corrected 
conductivity measurement is about 550, though, as already mentioned, this 
value is liable to variation corresponding with the weight of potato used. 
As we have shown in a previous paper, electrolytes diffuse out from 
cells even when they are surrounded by distilled water. After 48 hours’ 
immersion in conductivity water of twenty discs of potato, the conductivity 
of the liquid has increased to 144*8, only about a quarter of the value for 
complete exosmosis. The curve for distilled water is given in Figs. 4 and 6. 
The substances employed in this investigation were the following : 
Methyl alcohol Hopkin and Williams, free from acetone. 
Ethyl alcohol ‘ Absolute alcohol.’ 
Normal propyl alcohol Kahlbaum. 
Isobutyl alcohol Kahlbaum. 
Isoamyl alcohol Kahlbaum. 
Secondary I. Octyl alcohol, CH 3 (CH 2 ) 5 CHOH*CH 3 Kahlbaum. 
Acetone British Drug Houses, Analytical Reagent. 
Chloroform Hopkin and Williams, pure. 
Ether Tyrer, S. G. 0*717. 
Chloral hydrate Kahlbaum. 
