Inorganic Disinfectants 177 



With the salts, acids, and bases it appears from the researches of 

 Kronig and Paul* that ionization in solution plays an important 

 part in the destruction of micro-organisms. They found that 

 double metallic salts, in which the metal is a constituent of a com- 

 plex ion in which the concentration of the dissociated metal ions is 

 consequently very low, have very little germicidal power, but that 

 simple salts, in which the condition is reversed, have correspondingly 

 higher germicidal power. Dissociation, therefore, seems to have 

 much to do with the matter. 



Inorganic Disinfectants. 



ACIDS. These agents are seldom employed, since the concentration required 



makes them objectionable. 



ALKALIS. The same holds good with regard to these agents. 

 SALTS. In this group we find some of the most powerful and most useful 



germicidal substances. 



Copper Sulphate. It is curious and interesting that while this salt is highly 

 destructive to algae and other low forms of vegetable life, it is not of 

 much value for the destruction of bacteria. Its chief use is for the 

 destruction of the green alga? that sometimes render the water of 

 reservoirs dirty and offensive. Some of the salt contained in a gunny- 

 sack and permitted to drag to and fro over the surface of the water 

 behind a slowly rowed boat usually accomplishes the end, the actual 

 quantity dissolving in the water being almost infinitesimal. 

 Mercuric Chlorid (HgC^). This is probably the most generally useful 



as well as one of the strongest germicides. 



A study of its activity under varying conditions is instructive as exemplifying 

 the varying behavior of germicides under the varying conditions under which 

 they may be employed. 



First, it makes great difference whether the mercuric chlorid is added to the 

 substratum containing the bacteria, or whether the bacteria are added to solu- 

 tions of the germicide. 



Thus, when the salt is dissolved in gelatin in a concentration of i : 1,000,000, 

 anthrax bacilli cannot grow. If it is dissolved in blood-serum, the concentration 

 must be increased to i : 10,000 to prevent their growth. 



When the anthrax spores are dropped in solutions of the salt, Kronig and Paul 

 found that they were killed in twelve to fourteen minutes by 1 165 solutions; in 

 eighty minutes by i 1500 solutions, and in two hours by 1:1000 solutions. 

 When the reaction takes place in albuminous media Behring and Nochtf found 

 that much more time was required. Thus, the destruction of the spores by a 

 i : 200 solution required eighty minutes, and a i : 1000 solution twenty-four 

 hours to completely kill all of the spores. 



Laplace | and Panfili found that the addition of 5 per cent, of tartaric or 

 hydrochloric acid facilitated the germicidal action through the prevention of 

 albuminate of mercury formation. Liibbert and Schneider and Behring have 

 used sodium chlorid and ammonium chlorid. Both of these salts diminish the 

 germicidal action of the mercuric salt about one-half. Notwithstanding this, 

 however, the "antiseptic tablets" in common use for surgical and household 

 purposes contain one or both of these salts, added for the purpose of preventing 

 the precipitation of the mercuric compounds formed in the presence of alkaline 

 albuminous materials, such as blood, pus, sputum, feces, etc. 



The addition of about 25 per cent, of alcohol to the solution of the mercuric 

 salt greatly enhances its value. Strong alcoholic solutions are, however, less 

 useful than aqueous solutions, for the 95 or 100 per cent.' alcohol dehydrates the 

 micro-organisms and prevents the diffusion currents by which the mercury is 

 carried into their substance. 



* "Zeitschrift fur Hygiene," 1897, xxv, i. 

 t Ibid., rx, 432. 



'Deutsche med. Wochenschrift," 1887, 866; 1888, 121. 



'Ann. Ig. Roma," 1893, in, 527. 



