GERMICIDES AND ANTISEPTICS 327 



ethyl iodide, potassium iodate, 1 bromine, ethyl 

 bromide, chlorine, ferric chloride, and sodium fluo- 

 silicate - (' salufer ') destroy many microbes, includ- 

 ing Bacillus tuberculosis, Sarcina lutea, Bacterium 

 allii, B. cedematis maligni, and B. subtilis. 



Many of the derivatives of benzene and its horao- 

 logues are powerful germicides. Among these com- 

 pounds may be mentioned the following : benzoic 

 acid, sodium benzoate, sodium benzenesulphinate, 

 salicylic acid, sodium salicylate, carbolic acid, 

 sodium carbolate, etc. ; and the late Dr. T. Car- 

 nelley 3 proved that ' the para-compounds (of 

 benzene) are usually more powerfully antiseptic 

 than the corresponding ortho- and meta-compounds.' 4 

 For instance, it has been shown that of the three 

 sodium nitrobenzoates, it required 101-6 grammes 

 of the ortho-compound, 12'1 grammes of the meta- 

 compound, and 7*7 grammes of the para-compound 

 respectively to sterilise 1 litre of nutrient gelatine. 

 There are, however, a few exceptions to this rule : 

 among these are the three sodium hydroxybenzoates: 

 it required 11 '6 grammes of the ortho-compound 

 (sodium salicylate), 67'2 grammes of the meta- 

 compound, and 162'1 grammes of the para-com- 



1 Griffiths in Proc. Roy. Soc. Edinburgh, vol. xvii. p. 257. 



- Thomson in Chemical News, vol. Ivi. p. 132. 



:{ Journal of Chemical Society, 1890, p. 636. 



4 It may be stated that a derivative of benzene with a certain 

 empirical formula may exist in three isomeric modifications. 

 Although these isomerides have the same empirical formula, 

 their constitutional formulae, and consequently their properties, 

 are entirely different. This difference depends upon the relative 

 positions of the elements or groups of elements introduced into 

 the molecules. If we represent the orientation of the side- 



