on Endosmose and- Ex osmose. 319 



is put into the endosmometer, and the instrument is plunged 

 into a strong solution of gum, there is exosmose in the endos- 

 mometer ; the interior fluid descends in the tube, because the 

 current of the exosmose is stronger than the current of the 

 endosmose, owing to the greater density of the exterior fluid ; 

 but when pure water is the exterior fluid, and the fluid in the 

 endosmometer descends in the tube, this is no more an effect of 

 exosmose, but the simple result of a mechanical filtration. 

 Thus when water charged with sulphuric acid is put into the 

 endosmometer this liquid descends in the tube. 



I had before admitted that sulphuric acid was an agent 

 which produced exosmose, but it is not so, as can be ascer- 

 tained by making the opposite experiment. If pure water is 

 put into the endosmometer, and that instrument is plunged 

 into water charged with sulphuric acid, the water even de- 

 scends in the tube. These facts decidedly prove that there 

 is no current of endosmose nor of the exosmose directed from 

 the water towards the sulphuric acid, nor from the sulphuric 

 acid towards the water. This acid, however, by its superior 

 density to water, ought to produce endosmose when it is in 

 the endosmometer. If no effect is produced, it shows that its 

 chemical qualities render it completely incapable of producing 

 endosmose or exosmose. We find also that it is hostile to 

 this double action, for it has a tendency to destroy it when it 

 does exist. 



Thus, if a small quantity of sulphuric acid is mixed with a 

 solution of gum which is introduced into the endosmometer, 

 the fluid produces no endosmose, while the solution of gum 

 employed alone strongly produces that effect ; the gummy 

 fluid mixed with sulphuric acid descends gradually in the tube 

 of the endosmometer. If the quantity of sulphuric acid be 

 very small, there still remains a slight power of endosmose 

 in the gummy solution. We also sometimes see this acid solu- 

 tion which first descended in the tube of the endosmometer 

 resume a slight ascending motion, when the prolonged im- 

 mersion of the bladder in the water deprives the gummy solu- 

 tion of a part of the acid which it originally possessed. This 

 very important fact proves that there are inactive fluids with 

 respect to the property of producing the endosmose, and that 

 these fluids can communicate their inactive state to those 



