557 



is of the same order of magnitude as the heat effect. But with small 

 i the heat effect is much smaller than the variation of the free 

 energy. This latter is probably in connection with the small value 

 of the first differential heat of sorption in this substance. Most likely 

 there is no equality in the middle piece either, but only coirespond- 

 eiice in the order of magnitude. The experiments are, however, 

 not accurate enough to set forth this difference clearly. 



4. The Analogy of the Curves with those for ISfeioly-made Silicic 

 Acid and Zsigmondy and Anderson's Explication. 



As I already observed, the isotherm has the same typical shape 

 as that found by van Bkmmelen and later by Anderson for silicic 

 acid gel. The "turn", the point where the second «^-shaped curve 

 begins, lies at z'=0.57 and A = 0.65 for carbon. Also Bachmann 

 found a curve with a horizontal portion for the cocoanut carbon 

 examined by him (possibly even with two such pieces). And Behi. 

 and Andress found a curve of the same shape as mine in the carbon 

 examined by them. 



cal. 



20 



10 



Fig. 3. 



That also the curves of the heats of sorption correspond is shown 

 by fig. 3, in which I have represented Bellati and Finazzi's results ') 

 for newly-made silicic acid (temperature 12° — 20° C). Unfortunately 

 these carefully performed researches have so far escaped the notice 

 of the writers of the books on colloid chemistry, whence they have 

 not met with the recognition they deserve. The curve typically 



1) M. Bellati and L. Finazzi, Atti d. R. Instituto Veneto, Serie Vlll, Tomo i, p. 518. 



