104 



ENDOSMOSIS. 



circumstance that the excesses of density of 

 t'acli of these sulinc solutions over the density 

 of water are in the ratio of 2 to 1, or to this, 

 that the excesses in the power of capillary 

 ascent of each of these saline solutions over the 

 power of capillary ascent of water are in the 

 ratio of 2 to 1 ? In other words, is it the re- 

 spective density of the two fluids which regu- 

 lates or determines their endosmosis, or is it 

 the respective powers of capillary ascension of 

 the fluids severally ? 



The following experiment will solve this 

 question. We have seen above that a solution 

 of sulphate of soda and a solution of hydro- 

 chlorate of soda of equal densities being put 

 in relation to pure water, produce endosmoses 

 which are in the relation of two to one. Here 

 the difference of density does not interfere with 

 the regulation of the endosmosis ; we must then 

 see if it be regulated by the power of capillary 

 ascension. I prepared a solution of sulphate 

 of soda and one of hydrochlorate of soda, having 

 the same density 1.085, and tested their ca- 

 pillary ascension in the same tube in which we 

 nave seen pure water raised to a height of 1 2 

 lines at a temperature of + 10 degrees R. 

 I found that in the same tube and at the same 

 temperature the capillary ascension of the so- 

 lution of sulphate of soda was of 8 lines, 

 and that of the solution of hydrochlorate of 

 soda was of 10 lines. The excess of the capil- 

 lary ascension of water above that of the solu- 

 tion of sulphate of soda is consequently 4 ; 

 the excess of the capillary ascension of water 

 above the solution of hydrochlorate of soda is 

 2. These two excesses are in the relation of 

 two to one, a relation which also measures the 

 endosmosis produced with the concurrence of 

 water by each of these two solutions of equal 

 density. The result of this is that the capillary 

 ascension, or power of capillary ascent, of fluids 

 governs their endosmosis, and that their density 

 only intervenes in this case as the determining 

 cause of their capillary ascension. But how 

 does the capillary action operate here ? This ap- 

 pears to be difficult to determine. The capillary 

 action never carries fluids out of the canals in 

 which it takes place ; how then apply this action 

 to the phenomenon of double permeation, which 

 takes place in endosmosis and exosmosis ? 

 This double permeation, which carries two he- 

 terogeneous fluids towards each other, seems 

 as though it were the result of the reciprocal 

 attraction of the two fluids, of their tendency 

 to associate by admixture. In experiments of 

 endosmosis made with a dense fluid and water, 

 the tendency to mix is favoured by the respec- 

 tive positions of the two fluids; the dense 

 fluid is above and the water below. This dis- 

 position may possibly be one cause which fa- 

 vours the reciprocal mixture of the two fluids, 

 whose specific gravity would tend to place 

 them in an inverse situation to that given them 

 in the experiment. This does not take place 

 when experiments on endosmosis are made 

 with alcohol and water ; then the alcohol, spe- 

 cifically lighter than water, is situated above 

 this latter fluid, and, notwithstanding this, the 

 endosmosis is exceedingly energetic ; we must 



then acknowledge that the specific gravity of 

 two fluids has not here the degree of influence 

 that might be supposed to belong to it at first 

 sight. We have consequently no means left to 

 explain the course of the two fluids towards each 

 other athwart the capillary canals of the parti- 

 tion which separates them, but their reciprocal 

 attraction or tendency to admixture. In ad- 

 mitting that such is the efficient cause of this 

 double permeation we must also necessarily 

 admit that this efficient cause is governed in 

 its operation by the capillary action of the par- 

 tition. 



Here another question presents itself, do 

 the two fluids accomplish their admixture 

 in the capillary canals themselves, or do they 

 cross the partition by different capillary canals, 

 so that neither fluid mixes with its opposite 

 fluid until the moment of its exit from the 

 capillary canals? On the latter hypothesis it 

 were necessary to admit that the number and 

 diameter of the capillary canals followed sepa- 

 rately by each of the two fluids must be per- 

 fectly equal, for, without that, how would the 

 general result of this double permeation, a result 

 which is explained by the quantity of endosmo- 

 sis, be in exact relation with the capillary action 

 on the two fluids? Now it is repugnant to 

 reason to admit any such perfect equality among 

 all the capillary canals, or to suppose an equal 

 number especially fitted for the transmission of 

 each of the two fluids. It must then necessarily 

 be allowed that the transmission of the two op- 

 posite fluids takes place by the same capillary 

 canals, and that consequently this double 

 movement of transmission takes place by a 

 reciprocal penetration of the two fluids. 



The preceding theory, with which I was at 

 one time inclined to rest satisfied, and which, 

 indeed, seemed to be based on a sufficiently 

 firm foundation, was however brought into jeo- 

 pardy by a discovery which I made subse- 

 quently, in regard to the phenomena of endos- 

 mosis exhibited by certain acids separated 

 from pure water by a layer of animal mem- 

 brane. 



In the earliest experiments I made on the 

 endosmosis of the acids, I observed a number 

 of anomalous phenomena, for which I felt my- 

 self incompetent to assign any sufficient reason. 

 I had always placed the acids above the water, 

 from which they were separated by a layer of 

 animal membrane. Certain acids, such as the 

 hydrochloric, at very different degrees of den- 

 sity, and nitric acid only at pretty high degrees 

 of density, gave me an endosmosis, the current 

 of which was directed from the inferior water 

 towards the superior acid, so that the acid rose 

 gradually in the tube of the endosmometer. 

 On the other hand, I had always found the 

 sulphuric acid pretty largely diluted, and the 

 hydrosulphuric acid, under the same circum- 

 stances as the acids mentioned above, gradually 

 to sink in the tube of the endosmometer. [ con- 

 cluded from this that these acids did not occasion 

 any endosmosis, and that they passed mechani- 

 cally, and merely in virtue of their gravity, 

 athwart the animal membrane to mingle with 

 the water. I had ulso found that the sulphuric 



