44 



Introduction. 



Traube discovered the possibility of producing mem- 

 branes by chemical precipitation, at the plane of contact 

 between two solutions, which could be used instead of or- 

 ganic membranes to study osmotic pressure, and later 

 Pfeffer devised the apparatus represented in Fig. 7, with 



FIG. 7. Pfeffer*s apparatus for measuring osmotic pressure. 



which he was able to measure osmotic pressures of very 

 high intensity and with a fair degree of accuracy. He used 

 a porous porcelain cell Z, with three glass pieces, t, v, r, 

 put together with sealing wax in the manner represented 

 in section in the left of the figure, where the method and 

 arrangements for measuring the pressure are also shown 

 at a, m. The complete apparatus, in working order, is 

 represented at the right in the same figure. 



