100 



ENDOSMOSIS. 



through the capillary conduits of the plate, and 

 this flow would have become perceptible by 

 the sinking of the water in the tube, the inte- 

 rior of which was only two millimeters in dia- 

 meter. 



The result of this experiment was that the 

 plate of marble, which was four centimeters in 

 diameter, did not lose by filtration, in one 

 day, more than the small quantity of water 

 capable, by its subtraction, of lowering its 

 level one millimeter and a half in the tube. 

 I next tried syrup in this endosmometer, the 

 reservoir being plunged into pure water ; but 

 no endosmosis was induced. I now reduced 

 the thickness of the plate of marble to one 

 millimeter and a half; in this state it lost by 

 filtration, in the course of a day, eleven mil- 

 limeters of water measured by the tube. The 

 .permeability of this plate was, as may be per- 

 ceived, very sensibly increased : still the en- 

 dosmometer which it closed when filled with 

 syrup showed no indications of endosmosis. 

 1 reduced the thickness of the plate of marble 

 to one millimeter. In this state it lost by fil- 

 tration, in the space of a day, twenty-one milli- 

 meters of water measured in the tube. I put 

 into the endosmometer, which this plate of 

 marble closed, the same syrup which had been 

 used in the preceding experiments, and the 

 density of which was 1.12, and I now ob- 

 tained an endosmosis which manifested itself 

 by an ascension of seven millimeters in four- 

 and-twenty hours. This last experiment proved 

 to me that carbonate of lime was not, as I had 

 hitherto found it, totally without the power to 

 .produce endosmosis. I wished to compare 

 -this plate of marble with a piece of bladder of 

 the same surface under the double point of 

 view, of their permeability, and their respec- 

 tive properties of producing endosmosis. Having 

 therefore taken off the plate of marble which 

 closed the endosmometer, I replaced it by a 

 piece of bladder whose permeability to water I 

 measured in the same manner as above. I found 

 this permeability very nearly equal to that of 

 the plate of marble of on-e millimeter in thick- 

 ness. I then put into this endosmometer 

 some syrup similar in density to that which I 

 had used in the same endosmometer closed 

 with the plate of marble. The endosmosis 

 which I obtained raised the syrup seventy-three 

 millimeters in three hours. Thus the permea- 

 bility to water being equal in the bladder and 

 in the plate of marble, the endosmosis pro- 

 duced by the first was to the endosmosis pro- 

 duced by the second as 584 is to 7, a most 

 extraordinary difference, and difficult to be 

 accounted for. These experiments prove that 

 carbonate of lime is but very little apt to pro- 

 duce endosmosis, in which it differs singularly 

 from baked clay, thin laminae of which are 

 almost as apt to produce endosmosis as organic 

 membranes. , 



The varieties of sulphate of lime which may 

 be employed in endosmometrical experiments 

 are riot sufficiently numerous or of sufficient 

 variety of permeability for it to be possible to 

 appreciate the properties of this substance in 

 relation to endosmosis. I found that the sul- 



phate of lime used in the manufacture of 

 plaster in the environs of Paris, employed in 

 thin plates to close an endosmometer, did not 

 produce endosmosis. But this mineral is per- 

 haps too easily permeable. In fact it is found 

 impossible to obtain endosmosis when the in- 

 terior fluid of the endosmometer flows easily 

 by filtration, in virtue of its weight, through 

 porous plates. I should say as much of plates 

 of freestone (gres) which I have employed 

 without success in these experiments, but that 

 I recollect to have obtained the phenomenon 

 in a very slight degree with a plate of freestone 

 very close-grained and very little permeable to 

 fluids. 



I have tried a variety of experiments shew- 

 ing that an increase of temperature increases 

 endosmosis. This result has been confirmed 

 by repeated experiments. 



The quantjty of the same fluid introduced 

 by endosmosis, and with the same sort of per- 

 meable partition, is generally in proportion to 

 the extent of surface of this partition. The 

 following experiment demonstrated this fact. 

 I took two endosmometers, the membranes of 

 which, taken from the same bladder, were of 

 diameters in the relation of one to two ; I filled 

 the reservoirs of these two endosmometers with 

 syrup of equal density, and then plunged them 

 into pure water. I had taken care to weigh 

 them previously with great exactness. After 

 continuing the experiment for two hours, I 

 weighed the instruments afresh, and found in 

 the large endosmometer four times as great an 

 increase of weight as in the small one, which 

 proved that the first had introduced, by endos- 

 mosis, four times as much water as the second. 

 This relation was exactly that of the extent of 

 surface of their respective membranes, the 

 diameters of which were as one is to two, and 

 their surfaces consequently as one is to four. 



I have thus enumerated the effects; let us 

 now endeavour to ascertain their causes. 



The first idea which presented itself to my 

 mind to explain the phenomenon of endosmosis 

 was that it was owing to electricity. We know 

 that effects exactly similar to those of endos- 

 mosis are produced by means of the electricity 

 of the voltaic pile in the experiment of M. 

 Porret, inserted in the Annales de Chimie, 

 vol. xi. p. 137. This naturalist having divided 

 a vessel into two compartments by a septum of 

 bladder, filled one of the compartments with 

 water, and put only a small quantity in the 

 other. Having placed the positive pole of the 

 pile in communication with the compartment 

 full of water, and the negative pole with the 

 compartment containing little water, the fluid 

 was forced through the bladder from the full 

 compartment into the almost empty one, and 

 there rose to a higher level than that to which 

 it was reduced in the original full compart- 

 ment. 



I varied this experiment by applying it to my 

 own apparatus. I put pure water into an 

 endosmometer, the membrane of which was 

 plunged into water. I made the interior water 

 of the endosmometer communicate with the 

 negative pole of the pile, and the exterior 



