108 



ENDOSMOSIS. 



fore it, the endosmosis towards the water is 

 abolished, and then the column in tlie endos- 

 mometer begins to rise again slowly, until the 

 level of the external and included fluids corre- 

 spond. We, therefore, see that at a temjiera- 

 ture of + 10 cent., sulphuric acid, of the 

 density of 1.093, presents the current of endos- 

 mosis from the water towards the acid ; whilst 

 the density being 1.054, the endosmosis is 

 from the acid towards the water. Between 

 these two opposite endosmotic currents there 

 necessarily exists a main when no phenomena 

 of the kind occur. This mean, the tempera- 

 ture continuing -f 10, I find to belong to sul- 

 phuric acid of the density of 1.07. The two 

 fluids, divided by the animal membrane of the 

 endosmometer, penetrate one another athwart 

 the septum reciprocally and in equal measure, 

 so that the contents of the eudosmometer re- 

 main for a certain time at the same height in 

 the tube of the instrument ; subsequently the 

 contained fluid begins to sink in consequence 

 of the cessation of all endosmosis. These ex- 

 periments were necessarily undertaken when 

 the temperature was moderate or low ; the 

 phenomena detailed would not else have been 

 appreciable ; for in a warm atmosphere the 

 abolition of endosmosis by sulphuric acid is 

 accomplished so rapidly, that it is with diffi- 

 culty the slight current established in the first 

 instance can be observed. 



Sulphurous acid, of the density 1.02, sepa- 

 rated from water by an animal membrane, only 

 exhibits endosmosis towards the water; this 

 endosmosis is pretty active at first ; but after 

 the lapse of a brief interval the current ceases, 

 just as it does with the sulphuric acid. These 

 results I came to after a number of experi- 

 ments, the temperature being at one time + 5, 

 and at another +25 cent. 



Formerly I regarded the hydrosulphuric acid 

 as inactive in regard to endosmosis ; 1 assimi- 

 lated it, in this respect, with the sulphuric acid. 

 The fact, however, is that, like the sulphuric 

 acid, it has the property of producing endos- 

 mosis. The acid I employed was of the den- 

 sity of 1.00628. With a piece of bladder be- 

 tween this acid and water, the endosmosis was 

 constantly towards the water. This conclusion 

 was not influenced by variations of tempera- 

 ture between 4- 4 and -|- 25 cent. The ac- 

 tion was somewhat protracted, but the endos- 

 mosis never failed to cease after a certain time, 

 as in the case of the sulphuric acid. 



The nitric acid of considerable density exhi- 

 bits endosmosis towards the acid when sepa- 

 rated from water by a piece of animal mem- 

 brane. Thus, at a temperature of + 10 cent, 

 this acid (density 1.12 or higher) presents the 

 current flowing towards the acid. Under the 

 same circumstances, but of the density of 1.08, 

 the endosmosis is towards the water. Of the 

 density 1.09, the mean term between the two 

 opposite endosmoses is obtained. At higher 

 temperatures the nitric acid very speedily puts 

 an end to the phenomena of endosmosis, espe- 

 cially when its density is not very high, so that 

 it becomes difficult to perceive the very tran- 

 sient currents produced in the first instance. 



The hydrochloric is the most potent of all 

 the mineral acids in directing the current of 

 endosmosis from the water towards the acid. 

 Its density must be considerably reduced before 

 it offers the direction of the current changed, or 

 from the acid towards the water. At a tempe- 

 rature of + 22 cent, for instance, the hydro- 

 chloric acid has to be brought, by the addition 

 of water, to a density no higher than 1.003, 

 before it presents the endosmosis flowing to- 

 wards the water, from which, as understood, it 

 is divided by a layer of animal membrane. Of 

 greater density the eudosmosis is towards the 

 acid. When the temperature is lower than 

 +- 22", the same acid, of greater density, ac- 

 quires the property of causing endosmosis to- 

 wards the water. Thus, with the centigrade 

 thermometer at -f- 10, I found that hydro- 

 chloric acid of 1.017 density presented the 

 mean term between the two opposite eudosmo- 

 ses. At the same temperature hydrochloric 

 acid, of 1.02 density, presented endosmosis to- 

 wards the acid, and of 1.015 density, endos- 

 mosis towards the water. Under a higher 

 temperature, however, and of the latter density 

 (t.015), the endosmosis was towards the water, 

 so that a depression of 12 cent, in tem- 

 perature causes the mean term of the density of 

 hydrochloric acid, which separates the two op- 

 posed endosmoses, to rise from that of about 

 1.003 to that of 1.027; that is to say, the 

 quantity of acid added to the water must be 

 increased almost six-fold to produce the same 

 effects. 



In the present state of our knowledge, we 

 find it quite impossible to give any explanation 

 of the remarkable phenomenon exhibited in the 

 changes of direction of the endosmotic currents 

 according to the degree of density of the acid 

 and the temperature. The singularity of this 

 phenomenon will appear the greater when the 

 following observation is taken into the account. 

 Hitherto it was always by a layer of animal 

 membrane that I separated the acid from the 

 water. Instead of the animal membrane I 

 now tried the effect of one of vegetable origin. 

 We have seen above that oxalic acid, whatever 

 its density and under whatever temperature, 

 when separated from water by an animal mem- 

 brane, always exhibited endosmosis from the 

 acid towards the water. I filled a pod of the 

 colutea arborescens, which being opened at one 

 end only and forming a little bag, was readily 

 attached by means of a ligature to a glass tube, 

 with a solution of oxalic acid, and having 

 plunged it into rain-water, endosmosis was ma- 

 nifested by the ascent of the contained acid 

 fluid in the tube ; that is to say, the current 

 flowed from the water towards the acid. The 

 lower part of the leek (allium porrum) is en- 

 veloped or sheathed by the tubular petioles of 

 the leaves. By slitting these cylindrical tubes 

 down one side, vegetable membranous webs, of 

 sufficient breadth and strength to be tied upon 

 the reservoir of an endosmometer, are readily 

 obtained. An endosmometer, fitted with one 

 of these vegetable membranes, having been 

 filled with a solution of oxalic acid, and then 

 plunged into rain-water, the included fluid rose 



