OTHER PROPERTIES OF ELECTROLYTIC SOLUTIONS 297 



TABLE CXXIII. 



EXTINCTION COEFFICIENTS FOB SALTS OF ACETYLOXINDON AT DIFFERENT 

 CONCENTRATIONS IN ETHYL ALCOHOL. 



X = 436. 



Concentration: 1/100 1/1000 1/1000 1/2500 1/5000 



Thickness: 1cm. 1cm. 2cm. 5cm. 10cm. 



Ca . 214 220 226 217 



Sr 230 227 232 231 



Ba 230 238 240 236 



Li 259 263 255 250 258 



a 325 330 328 325 322 



K 339 338 333 325 340 



Rb 329 327 329 343 341 



Cs 390 409 393 383 395 



Tl 325 328 337 330 



inclined to account for these variations on the basis of a slight rearrange- 

 ment in the chromophore group, somewhat similar to that established in 

 the case of the salts of the oximidoketones, a thoroughly satisfactory ex- 

 planation of this behavior of the above solutions does not exist. 



From the foregoing, it appears that, in solutions of salts which have 

 stable chromophores, the absorption spectra are independent of the con- 

 dition of the salt, and accordingly we may conclude that, whether an ion 

 is combined or uncombined, the absorption spectrum remains unchanged. 

 Where changes occur, reactions are to be looked for, the nature of which, 

 however, has not been established in all cases. 



5. The Electromotive Force oj Concentration Cells. The properties 

 of a solution are determined by the values of the variables which fix its 

 state. If the solution is subject to the action of external forces, its prop- 

 erties will vary accordingly. Under such conditions the thermodynamic 

 potential of the dissolved substance suffers a change and electromotive 

 forces naturally arise under suitable arrangement of solutions and elec- 

 trodes. Such, for example, is the case when solutions are subjected to 

 centrifugal action. 23 We shall, however, confine ourselves here to a con- 

 sideration of electromotive forces arising as a result of concentration dif- 

 ference. Wherever we have a surface of discontinuity between two 

 electrolytes, or between an electrolyte and a metal, an electromotive 

 force will in general arise. 



For a system under the action of external forces, the condition for 



Tolman, Proo. Am. Acad. tf, 109 (1910). 



