532 Prof. A. B. Macallum. Acineta tuberosa : [Feb. 19, 



Out of a large number of solutes used in these experiments only two, 

 caffein and anilin, gave values which approximated the values postulated by 

 do - 



the equation S = — — - . _, while in the case of the others the experi- 



mentally ascertained values greatly exceeded the theoretic values. Thus, 

 in a sodium glycocholate solution of 025-per-cent. concentration, the surface 

 condensation on the droplets of hydrocarbon oil was 5 x 10 -6 grm. per cm. 2 , 

 that is, the directly ascertained value was about 70 times the theoretic 

 value. When mercury was used the ascertained value exceeded the 

 theoretic about 25 times. In sodium oleate solutions the directly 

 determined value was about 100 times the theoretic. With Congo red, 

 methyl orange, and sodium hydrate the experimentally ascertained values 

 were respectively 25, 43, and 20 times the values derived from the G-ibbs 

 equation. Even if errors in calculation were allowed for in every case, the 

 excess of adsorbed solutes was still so great that Lewis suggested, as a 

 possible explanation for the great discrepancy, that the adsorbed material 

 is in a gelatinised or colloidal condition on the surfaces of the droplets of oil 

 or mercury. 



Lewis found also that in the case of inorganic salts the quantity adsorbed 

 exceeded the theoretic amount, but it was chiefly the cation that was so 

 affected. In silver nitrate the silver adsorbed was 5 times in excess ; in 

 cupric chloride the copper was 17 ; and in potassium chloride the potassium 

 was more than 30 times the calculated amount. This excess of the cation 

 is, in Lewis' opinion, probably clue to electrical effects, since the oil used is 

 negatively charged, and the potential difference between the oil and the 

 water is approximately - 05 volt. 



The diameter of a water molecule is, according to Kundt and Warburg (5), 

 3*39 x 10 -8 , and, consequently, the diameter of its sphere of attraction at the 

 oil-solution interface would be 6'78 x 10 -8 cm., but Lewis, accepting the 

 range as equivalent to that postulated by Parks (14), namely, 13*4 x 10~ 6 cm., 

 and using also the value 5 - 4x 10 -6 grm. for the amount adsorbed per cm. 2 

 from a - 25-per-cent. sodium glycocholate solution as experimentally 

 determined, calculated that the concentration of the bile salt in the 

 superficial layer at the oil-solution interface was 40"3 per cent., or 160 times 

 that obtaining in the rest of the solution. If, however, we assume that the 

 range of molecular attraction is smaller than that postulated by Parks 

 then the concentration of the bile salt at the interfacial surface must be 

 extraordinarily high. 



How such a concentration can obtain we do not know, but an explanation 

 may be tentatively suggested. It is not certain that the solute adsorbed 



