92 BACTERIOLOGY. 



moniurn (NH 4 ) and hydrogen (H) ; while the electro- 

 negative anions include the halogens, the acidic radicals 

 (such as NO 3 and SO 4 ), and hydroxyl. 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 con- 

 centration of the metal ion is very slight, have but 

 feeble disinfecting 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 in- 

 verse ratio to their atomic weights. 



The disinfecting activity of watery solutions of mer- 

 curic chloride is diminished by the addition to them 

 of other halogen compounds of metals and of hydro- 

 chloric acid. It appears probable that this is due to 

 obstruction offered to electrolytic dissociation. 



The disinfecting activities of watery solutions of mer- 

 curic nitrate, mercuric sulphate, and mercuric acetate are 

 increased by the moderate addition of sodium chloride. 



In general, acids disinfect according to the degree 

 of their dissociation i. e. y according to the concentra- 

 tion of their hydrogen ions in the solution. 



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 

 Electrolytic Dissociation," etc., by H. C. Jones, Ph. D., Johns Hopkins 

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



