47 



ions in casein, those by Dr. Rungenberg de Jong did so in anivliuii '). 

 Especially this positive effect is, therefore, a forcible aignment in 

 favonr of our view. 



4. Two objections may, however, be raised. The first is: is NH, 

 and also is SO^ in benzene an electrolyte? For the formation of an 

 OH-ion from XH,OH, resp. an H-ion from H,SOj the presence of 

 water is reqnired. If it is, however, calculated iiow much water is 

 required with the very small concentrations in question, values are 

 found which are only a small part of the solubility of water iu 

 benzene, a quantity that is certainly always present in benzene that 

 has not been dried with particular precautions. 



A second objection might be supplied by the question whether 

 the electrolytes in benzene are sufficiently dissociated to put these 

 phenomena to their account. Walden's') investigations, however, 

 may reassure us in this respect. Equal dissociation in two solvents 

 is attained at dilutions that are to each other as the third 

 powers of the dielectricity constants, i.e. for the relation bezene- 

 water 4,7 X 1^^^- Hence the succession of the strengths is the same 

 in two solvents. If now according to Walden the a is calculated 

 for HCI in benzene, cone. 1 milol per litre, taking into account 

 that the constant from Ostwai,d's law of dilution varies proportional 

 to the concentration of the undissociated molecules, the value «=iO,32 

 is found. Here there is, therefore, a considerable ionisation. With a 

 weak acid, as benzoic acid, the dissociation is, indeed, moregreatlv 

 iowered by benzene than in the case that the substance is dissolved 

 in water, but in the concentrations in question here, it is yet not 

 less than '/joo of that in water. 



There is, however, a striking difference between the electro-viscous 

 phenomena in water and those in benzene. In water the curves for 

 cations of equal valency coincide, but this is not the case for our 

 curves, though they all have the H-ion as discharging ion ywith the 

 exception of HgCl,). It makes the impression that the real H-ion 

 concentration plays a part: for the anorganic acids discharge in the 

 order of their strength. The two organic acids are, indeed, stronger 

 than H,S, but organic anions always counteract the discharge through 

 their greater absorbability, the aromatic ion more strongly than the 

 aliphatic one, thus compensating its greater strength. The exceedingly 



') Still unpublished; compare however for casein VV. Pauli, Kolloidcheraie der 

 Eiweisskörper. 81 et seq. (Dresden-Leipzig 1920) and for amylum M. Samec KoU. 

 Beih. 4, 132 (1913), 5, 141 (1914) etc. 



-) P. Walden. Z. physik. Chem. 94. 363 (1920). 



