470 



Dr. F. G. Donnan on the 



CuS0 4 solution. Concentration = T ^ grm. equiv. per litre. 

 Temperature 21°-26° C. 



H. 



D. 



D 

 H' 



385 C.G.S. units. 

 707 „ „ 

 962 „ 



•0018 

 •0024 

 •0034 



•46X10- 5 

 •34xl0- 5 

 •35xl0- 5 



To test these results by means of the theory, it is only 

 necessary to calculate the value of i(V — U), where it must 

 be noticed that V and U are the velocities of the gram-mols. 

 in centim. per second under a potential-gradient of one C.G.S. 

 electromagnetic unit of potential per centim. From Ostwald's 

 Lehrhuch, vol. ii. p. 770, the molecular conductivity of CuS0 4 

 solutions for the highest dilution at 18° C. is 217 in Siemens 

 units, and therefore 230 in mho's. As the calculation is only 

 very approximate, we may put consequently 



(U + V)i8 °= 96540x2 xl0 8> 



From the same source, p. 612, we get ^f — rf = '^> a va ^ ue 



which may be regarded as fairly correct for temperatures 

 in the neighbourhood of 20° C. (according to Hittorf and 

 Bein, loc. cit.). Hence we obtain finally 



i(V-U) 18 o = 16xlO- 13 . 



The value of i(V-U) for temperatures 21°-26° C. will 

 probably be somewhat smaller. Of course the solution of 

 concentration =yg grin. -equiv. per litre is not by any means 

 completely dissociated; and by using the proper equation, 

 namelv, 



Lv 



Mm 

 L4-M ' 



Lv 



Mm v — u , ,11,. 



T^r- > — r~i we should obtain a 

 L + M 2 ' 



D 



H 



since v > u and therefore 



higher value for ^. Nevertheless this would never account 



for the difference between *39 x 10~ 5 as observed by Bagard 

 and 16 x 10~ 13 as deduced theoretically for the case of complete 

 dissociation. 



