Absorption Spectra of Dilute Solutions. 



tion of the dinitrophenol which is electrolytically dissociated in a 

 solution, a measurement of its extinction coefficient for any one 

 wave-length having been made. If x is the part which is dissociated 

 into its ions, the extinction coefficient of the solution (calculated for 

 unit concentration and 1 cm. layer) will be 



# e( un diss.). 



Table X contains the results of the measurements of a number of 

 solutions of dinitrophenol of different concentrations. For the experi- 

 mental details see Appendix, Table V. In Table X, % e,-, and e Uf 

 are the extinction coefficients for the solution actually measured, for 

 the ion, C 6 H 3 (N'O 2 )20, and for the undissociated molecule of dinitro- 

 phenol respectively. The values of e,-, as remarked above, are taken 

 as the mean of the measurements made with dilute solutions of the 

 potassium and ammonium salts. 



x the fraction dissociated is calculated from the equation given 

 above. 



Table X. 



The numbers under x calculated are the fractions of the substance 

 electrolytically 'dissociated calculated from the determinations of the 

 electrical conductivity of solutions of dinitrophenol made by Bader. 

 (' Zeit. Phys. Chem.,' vol. 6, p. 298, 1890). He found the dissociation 

 constant of dinitrophenol K = 0*008. This is connected with x by 



the formula K = . 



V, the volume in litres in which 1 gram molecule is dissolved, may 



be replaced by -, which gives 

 c 



