Mr Hill, Use of experimental method of preceding paper. 387 



Note on the use of the experimental method described in the 

 preceding paper. By A. V. Hill, Scholar of Trinity College, and 

 George Henry Lewes Student. 



AGDB is the tube containing the gelatine, which stretches 

 from AB to the bottom CD of the tube. Then the conditions 

 throughout the gelatine ACDB must be the same as if we had 

 double as much gelatine AEFB, and KCl (e.g.) solution at each 

 end. For in the first case the bottom of the tube hinders diffu- 

 sion across the plane AB: in the second case from considerations 

 of symmetry there can be no diffusion across the plane CD. 



Gg and Hh are the platinum electrodes. AG = -^= CE. 





Let y be the concentration at any point P measured a distance 

 X along the tube. 



Then we have the equation for the diffusion, 



dt dx" 

 if t is the time. 



A solution of this equation which satisfies all conditions is 



r=oa _j^] 



y^yo+ 2 Are 



■ f . rirx 



sm , 



a 



For (1) at ^ = 0, y = yo, the constant concentration of KCl. 



(2) at « = a, 2/ = 2/o- 



(3) y can be made equal to at ^ = 0. 

 We have at ^ = 



i) = yQ + ZAr sm ■ . 



1 <^ 



