SURFACES 29 



other experimenters with wool, filter paper, etc. Since the chemical 

 constitution of many of these substances is unknown and others can- 

 not be prepared free of electrolytes, H. BECHHOLD considered it de- 

 sirable to settle the problem by, using substances possessing definite 

 constitution and which were easily obtained in a pure state. As such 

 adsorbents, he chose naphthalin (CioH 8 , neutral), naphthol (Ci H 7 OH, 

 acid), naphthylamin (Ci H 7 NH2, basic), amidonaphthol (Ci H 6 OHNH 2 , 

 amphoteric). These substances were freely suspended in water and 

 shaken for several minutes with solutions of various dyes; they were 

 filtered off and washed until' the filtrate was practically colorless. 

 The dye solutions employed were those generally used in microscopic 

 technic. The results of my staining experiments are shown in the 

 accompanying table. From these experiments it is evident that in 

 most cases, even with the neutral naphthalin, there is at least a faint 

 staining. The coloration is so slight, that it certainly could not be 

 recognized in a microscopic specimen and it is evidently to be attrib- 

 uted to mechanical adsorption. It may be seen at a glance how re- 

 markably the staining differs, depending on the chemical constitution 

 of the stained substance, neutral naphthalin is not deeply colored 

 by any stain. Naphthylamin and amidonaphthol are always most 

 strongly stained by the acid dyes, and naphthol and amidonaphthol 

 by the color bases. Thus we see that the chemical constitution of the 

 adsorbent plays a very important part in the distribution of the 

 dissolved substance between the solvent and the dispersed phase. 

 BERCZELLER and CZAKI* reached analogous results with the adsorp- 

 tion of alkaloids (cocain, atropin, etc.), by various powders (starches, 

 coagulated albumin, which acted as weak acids and adsorbed most 

 strongly, whereas alkaline CaCOs adsorbed least) . That we are deal- 

 ing with electrochemical phenomena in the above cases is still more 

 evident when we observe how the addition of electrolytes affects adsorb- 

 ability. Wool, which is dyed particularly well by basic dyes in a 

 neutral bath, takes them up still better from an alkaline bath, but it 

 is also dyed in an acid bath with acid colors. Still better evidence 

 lies in the fact that the cations of neutral salts increase the dyeing 

 of acid colors in proportion to the valence of the cation (W. M. 

 BAYLISS). 



We must furthermore mention the fact that supplementary chemical 

 reactions may occur between adsorbent and adsorbed substances, 

 which may lead to a fixation that makes the process irreversible, i.e., 

 a true chemical combination may result. The occurrence of this 

 condition is characterized by the fact that it requires a certain 

 length of time, whereas according to H. FREUNDLICH, the adsorp- 

 tion balance is established in a few minutes. Moreover, such a de- 



