* JACQUES LOEB 189 



tions in m/128 HCl than in m/1,024 acid, on account of the negative 

 osmosis caused by solutions of acids, as the next chapter will show. 



Fig. 10 shows the difference in the influence of concentration upon 

 the rate of diffusion of water in the case of Na2HP04 and NaH2P04. 

 In the presence of the latter solution the water diffusing through the 

 membrane is negatively charged and the curve does not show the 

 initial rise and drop but shows only the gas pressure effect of the 

 solution. In the case of Na2HP04 water diffuses in the form of 

 positively charged particles and the curve shows the rise and drop 

 as described for neutral and alkaline salts in which the anion has 

 a higher valency than the cation. 



We can therefore state that for the diffusion of negatively as well 

 as positively electrified particles of water the law of van't Hoff is re- 

 versed within a certain range of concentrations of electrolyte — in the 

 extreme between about m/256 and m/4 — inasmuch as in this range 

 the attraction of a solution of an electrolyte for pure water diminishes 

 with increasing concentration. 



III. Negative Osmosis. 



Dutrochet,^ Graham,"* and Flusin^ have observed a striking phenom- 

 enon of negative osmosis in certain acids; namely, that the stream 

 of liquid diffuses through pig's bladder from acid to pure water, in- 

 stead of in the opposite direction. This was observed for tartaric 

 and oxaHc acids. Flusin tries to explain the phenomenon on the basis 

 of a difference in degree of imbibition or swelHng of the two sides of 

 pig's bladder, one side being in contact with pure water where the 

 swelHng is sHght, the other being in contact with acid where the swell- 

 ing is great. Bartell, and Bartell aind Hocker^ have observed 

 negative osmosis through porcelain even in the case of some neutral 



^ Dutrochet, H., Ann. chim. et. phys. 1835, Ix, 337. 



" Graham, T., Phil. Tr., 1854, cxliv, 177. 



^ Flusin, G., Ann. chim. et phys., 1908, xiii, 480. For a discussion of the lit- 

 erature see Hober, R., Physikalische Chemie der Zelle und der Gewebe, Leipsic, 

 4th edition, 1914, 248. 



« Bartell, F. E., /. Am. Chem. Soc, 1914, xxxvi, 646. Bartell, F. E., and 

 Hocker, C. D., /. Am. Chem. Soc, 1916, xxxviii, 1029, 1036. 



