DISINFECTION. 413 



and bases, into electropositive and electronegative con- 

 stituents into their ions takes place in watery solutions. 

 While in general the salts in watery solution are much 

 more actively dissociated than the acids and the bases, the 

 degree of dissociation of the various salts of a metal is 

 dependent upon the nature of the acid-ion, and that of the 

 same salt in turn upon the dilution. 



As the chemic and physical properties of solutions are 

 dependent upon the degree and the character of the ioniza- 

 tion, it has developed that also the disinfectant activity of 

 equimolecular solutions is influenced by the dissociation, 

 so that, for instance, solutions of mercurial salts are the 

 more active the more mercury they contain, not by weight- 

 percentage, but in the form of ions. For this reason solu- 

 tions of mercuric chlorid exceed in activity solutions of all 

 other mercurial salts. 



In the course of their investigations Paul and Kronig 

 discovered another series of laws. Thus, the acids act in 

 general accordance with their electrolytic dissociation (ex- 

 cept hydrofluoric acid, nitric acid, trichloracetic acid), and 

 likewise the bases in accordance with the concentration of 

 the hydroxyl-ions contained in the solution. It has also 

 been shown that the oxidizing agents nitric acid, chromic 

 acid, chloric acid, persulphuric acid, and permanganic acid 

 are active in accordance with the position that they 

 occupy in the scale of oxidizing agents by reason of their 

 electric activity. The halogens chlorin, bromin, iodin 

 whose disinfecting activity on the whole, in correspondence 

 with their chemic activity, diminishes with increase in atomic 

 weight, play a specific role. 



Whereas ionization has thus proved itself an index for 

 both the chemic and the disinfectant activity of salts, acids, 

 and bases in general, the inorganic disinfectants there 

 exists, according to Scheurlen and Spiro, another large 

 group of disinfectants, whose activity is not dependent upon 

 the action of ions, but upon "molecular action," and in 

 connection with which the entire undissociated molecule 

 must be taken into consideration. The mode of action of 

 this class of substances, the principal representative of 

 which is carbolic acid, can be explained, as Spiro has 

 recently shown, by analogy with the laws for the division of 

 a body between two solvent agencies : that is, the condi- 

 tion present is not, as in the first class of disinfectants, one 



