SURFACES 



23 



This is the equation of a line. If the logarithms of the values found 



f or : an d for c, of different concentrations of the substances under 



j m 



examination, are carried onto a rectangular system of co-ordinates, 

 these points would lie on a line, provided the substance was sub- 

 jected only to pure mechanical adsorption. 



As the simplest example we shall choose the curves and data 

 which H. FREUNDLICH * derived from his studies of the adsorption 

 of certain fatty acids by charcoal. Fig. 3 shows the adsorption curve 



FIG. 3. Adsorption of fatty acids by charcoal. 



(After H. Freundlich.) 



of acetic acid, propionic acid and succinic acid, in direct graphic 

 representation as we have explained on page 22. 



They are derived from the following somewhat abridged data of 

 FREUNDLICH: 



