Investigations dealing with the State of Aggregation. 403 



their solutions, those with the lowest surface tensions exhibiting the greatest 

 disaggregating action.* 



The disaggregating power has been determined in the following instances : 



(1) As regards their power of dispersing the globulins (this series, Part I). 



(2) Their action on inhibiting the formation of methylene iminopeptones 

 (this series, Part II). (3) Their influence on the critical solution tempera- 

 tures of phenol and water, and their effect on the solubility of certain salts 

 in water (this series, Part III).t In the form of calcium salts these acids 

 also exhibit an inhibiting action on the formation of the chelate gel when 

 the surface tensions of the solutions is lower than that of pure water ; in this 

 case, the greater the concentration, the greater would be the time required 

 for clot formation if the lowering of surface tension impeded aggregation ; 

 the increase in the concentration of the calcium ions, however, diminishes 

 the time, the calcium and anions acting antibatically. In spite of this fact, 

 however, the general relationship between surface tension and disaggregating 

 capacity is clear from the experiments.^ 



The above mentioned salts form, therefore, a perfectly well-defined " series " 

 as regards their disaggregating capacity, and it was of special interest to 

 ascertain whether their power for flocculating colloids ran in any parallel 

 with this action. One other sodium salt was added to the number investi- 

 gated, viz., that of benzene sulphonic acid. This belongs to a class of salts 

 exhibiting, what Neuberg terms " hydrotropic " phenomena,§ that is, the 

 capacity of rendering certain substances soluble in water which are only 

 very slightly soluble in the absence of salts. A similar phenomenon was 

 recorded by one of the authors (see this series. Part III), and ascribed by 

 him to the effect of the salt in lowering tiie surface tension of the aqueous 

 solution and thus markedly increasing the disaggregating power of the 

 solvent. It is recorded in the sequel that the normal solution of sodium 

 benzene sulphonate has a very low surface tension. Benzene sulphonic acid 

 is, furthermore, a strong acid as compared with salicylic acid, and, for this 

 reason alone, the addition of its sodium salt to the list of those investigated 

 was desirable. 



As both negative and positive sols were included in these researches, and 

 as the former are more sensitive to the action of the cations and the latter to 



* There is very little diflference between the surface tensions of the normal benzoate 

 and salicylate solutions. The latter, which has a slightly greater surface tension in 

 normal solution, has a greater disaggregating power, which may be ascribed to the differ- 

 ences in the viscosity. For discussion on these points, see Part I of this series. 



t ' Eoy. Soc. Proc.,' B, vol. 83, pp. 96, 113, 119 (1910). 



X Schryver, ' Eoy. Soc. Proc.,' B, vol. 87, p. 366 (1914). 



§ ' Biochem. Zeitsch.,' vol. 76, p. 107 (1916). 



