PHENOLS AND ORE SOLS 133 



tincture of iodine — 4-5 per cent, iodine in 70 per cent, alcohol, together with 2 per 

 cent, potassium iodide to stabilize the iodine— is one of the best skin disinfectants 

 known. Though the bactericidal actis^ity of alcohol is negUgible below 10-20 per 

 cent., it may prove bacteriostatic to many organisms in concentrations as low as 

 1 per cent. (Wirgin 1902). As an antiseptic for the preservation of vaccines, 

 25 per cent, alcohol has been found to be rather more potent than 0-5 per cent, 

 phenol (see Cruickshank et al. 1942). Commercial alcohol as a rule contains spores, 

 so that for surgical or biological use it should be filtered through a Berkefeld or similar 

 candle (not a Seitz, which is effective only in the presence of water) or distilled. 



Eitchie (1899) showed that the germicidal action of different alcohols increased 

 with their molecular weight, ethyl alcohol being more potent than methyl, propyl 

 than ethyl, and butyl than propyl alcohol. This has been confirmed by subsequent 

 workers (Wirgin 1904, Tilley and Schaffer 1926, Tilley 1939, Lockemann, Bar and 

 Totzeck 1941). For disinfection of the skin, 80 per cent, propyl alcohol is particu- 

 larly useful ; it is more bactericidal than ethyl alcohol, it is a better fat solvent, 

 and it is not so volatile. (For a detailed review of the disinfectant action of alcohol, 

 see Sobernheim 1943, and for its value as a hand disinfectant, see Ahlfeld and 

 Vahle 1896, Neufeld and Schiemann 1943). 



The ethers are possessed of some degree of germicidal activity. Cultures of 

 non-sporing bacteria incubated in an atmosphere saturated with the vapour of 

 diethyl ether — C2H5OC2H5 — exhibited no growth ; subcultures showed that the 

 organisms had been killed in a period varying from about 1 to 48 hours (Topley 

 1915). Direct immersion of Bad. coli in 50 per cent, ether proved fatal in about 

 3 minutes at room temperature. On the other hand, exposure of CI. septicum to 

 pure ether failed to destroy the spores in 24 hours. According to Kronig and 

 Paul (1897) ethereal solutions of disinfectants are almost without effect on anthrax 

 spores. 



Phenols and Cresols.- — Under this heading we shall consider the action of those 

 bodies that are obtained from the destructive distillation of coal, and that pass 

 over between the temperatures of 170° and 270° C. Phenol itself in certain pro- 

 portions is able to pass into solution in water, but most of the bodies in this group 

 do not do so ; when mixed with water they form emulsions of varying degrees of 

 fineness. Their mode of action is therefore different from the action of the germi- 

 cides which we have so far considered. The phenols and cresols have a fairly 

 high germicidal activity when employed in solutions above a given concentration ; 

 but it requires quite a low degree of dilution to deprive them entirely of this 

 activity. In this respect they differ markedly from the saline disinfectants (see 

 p. 143). 



It has been supposed that phenol acts by its formation in contact with pro- 

 teins of an insoluble albuminate and of other chemical compounds. Reichel 

 (1909), however, who studied the dispersion phases of phenol between oil and 

 water, brought evidence to suggest that the action is not so much chemical as 

 physical, the phenol being capable of passing into solution in such substances as 

 coagulated albumin, certain lipins, and the cytoplasm of bacteria. He suggests 

 therefore, that its disinfectant action results from its penetration into the bacterial 

 cell in the form of a colloidal solution. 



The emidsified disinfectants, such as the cresols, probably act in much the same 

 way as phenol, but their germicidal activity is usually somewhat higher. By 

 virtue of their emulsoid state, their particles are adsorbed on to the surface of 



