96 BACTERIOLOGY 



ions, which are atoms or groups of atoms having electro- 

 positive and electro-negative characteristics. According 

 to this theory, salts, when dissolved in water, undergo 

 electrolytic dissociation into metallic and acidic ions, the 

 former being the electro-positive cation, the latter the 

 electro-negative anion; sodium chloride, for example, re- 

 solving itself, under these conditions, into its sodium, 

 or metal ion, and its chlorine, or acidic ion. The electro- 

 positive cations, according to Ostwald, comprise the metals 

 and metal-like radicals, such as ammonium (NH 4 ) and hydro- 

 gen (H); while the electronegative anions include the halo- 

 gens, the acidic radicals (such as NO d and S0 4 ), and hydrosyl. 1 

 Using this theory as the basis of their investigations, Kronig 

 and Paul reached the following conclusions with regard to 

 the action of chemical disinfectants: 



The germicidal value of a metallic salt depends not only 

 upon its specific character, but also upon that of its anion. 



Solutions of metallic salts in which the metallic part is 

 represented by a complex ion and in which the concentra- 

 tion of the metal ion is very slight, have but feeble disin- 

 fecting activity. 



The halogen compounds of mercury act according to the 

 degree of their dissociation. 



The disinfecting power of the halogens chlorine, bromine, 

 iodine (as well as their compounds) is in inverse ratio to 

 their atomic weights. 



The disinfecting activity of watery solutions of mercuric 

 chloride is diminished by the addition to them of other 



1 Consult Ostwald's Lehrbuch der Allg. Chemie; or Muir's transla- 

 tion of Ostwald's Solutions, p. 189, published by Longmans, Green & 

 Co., London and New York, 1891. Also The Rise of the Theory of Elec- 

 trolytic Dissociation, etc., by H. C. Jones, Ph.D., Johns Hopkins Hospital 

 Bulletin, No. 87, June, 1898, p. 136. 



