410 S. GARD AND O. MAAL0E 



4. Halogens 



Earlier reports on the action of hypochlorite and chloraniines were some- 

 what conflicting. One of the reasons for this was unawareness of the role 

 played by nitrogen-containing impurities present in the test material. Trask 

 et at. (1945) studied this question and found, not only that much larger doses 

 of hypochlorite were required to inactivate vu'us in a medium rich in organic 

 material, but also that higher residua] chlorine concentrations were needed. 

 Thus, impurities seemed to act partly by consuming chlorine and partly by 

 affording some kind of extra protection against the chemical agent. This 

 phenomenon was later explained by findings concerning the mechanism of 

 chiorination. Chlorine (CI 2) can exist as such in aqueous solution only at a 

 very acid pH. Otherwise it reacts with water, forming hypochlorous acid. 

 This in turn, at alkaluie pH, dissociates hypochlorite ions. In the presence of 

 ammonia or amines a chain of reactions is incited, by which successively 

 mono-, di-, and trichloramines are formed. The latter, finally, are oxidized 

 by addition of further chlorine with formation of chlorides ("break point" 

 chiorination). Residual chlorine may be either "free" (Clg, hypochlorous acid, 

 hypochlorite ions) or "bound" (chloramines). According to Lensen et al. 

 (1949), the inactivating capacity of organically bound chlorine is poor, 

 whereas free chlorme is highly virucidal, particularly in the acid pH range. 

 At an alkaline pH the negatively charged virus protein presumably offers a 

 greater resistance against diffusion of the likewise negatively charged hypo- 

 chlorite ions, thereby affording a better protection of the nucleic acid. In 

 addition, the oxidation reduction potential of hypochlorite is a function of pH. 



In a recent study of the kinetics of chiorination, Kelly and Sanderson 

 (1957) observed deviations from the first-order type of reaction, similar to 

 those described for formaldehyde and urea. 



Iodine, cautiously applied at slightly acid pH and in the presence of an 

 excess of potassium iodide, acts specifically on sulf hydryl groups without any 

 inactivatmg effect (Anson and Stanley, 1941). Depending upon the configura- 

 tion of the virus protein sulfenyl iodides or — S — S — , linkages are formed 

 (Fraenkel-Conrat, 1955). At lower concentrations of potassium iodide and 

 higher pH primarily di-iodot3n:osine substitution is achieved, which affords 

 the protein a new immunological specificity (Boltralik and Price, 1954) with- 

 out necessarily inactivating the virus. Like chlorine, iodine is a powerful 

 oxidant in the acid pH range and under these conditions has a strong viru- 

 cidal effect. 



Scattered observations on inactivation by several other oxidants have 

 been pubhshed, e.g., potassium permanganate in concentrations of 0,001 to 

 0.005 % (Schultz and Robinson, 1942; Dunham and MacNeal, 1944); potas- 

 sium dichromate (Schultz and Robinson, 1942); nitrites (Schramm and 

 Muller, 1940; Zamenhof et al, 1953). 



