OSMOTIC AND MEMBRANE EQUILIBRIA 207 



its neighbouring phases, and completely separated from the 



remaining phases. 



Phase a. Containing, inter alia, species A and B. 



Membrane 1. Permeable to B only. 



Phase /3. Containing, inter alia, species B and C. 



Membrane 2. Permeable to C only. 



Phase y. Containing, inter alia, species C and A. 



If all the species A, B, C are electrically neutral, the two 

 membrane equilibria are determined completely by the con- 

 ditions 



4 = Mb. (103.1) 



nZ = 4, (103.2) 



*c f'c, 



but in general 



f^l^t^:, (103.3) 



that is, the phases y and a are not in equilibrium as regards 

 the species A. If the phases y and a be now brought into 

 contact through a membrane permeable to A only, there will 

 be a flow of A from the one to the other in a direction 

 determined by the sign of /x][ — n". This flow will, of course, 

 upset the other membrane equilibria, which will readjust them- 

 selves. The flow of A through the auxiliary membrane and the 

 accompanying readjustments will not cease until either the 

 phases y and a are again separated, or the conditions 



the "chemico-motive force" of the cell for the component A. 

 Bringing the phases y and a into contact through a membrane 

 permeable only to A we may call short-circuiting the cell, and 



