DISINFECTANTS. 373 



about 15% of phenol. Such powders gradually lose their 

 phenol on exposure to air. Pure phenol is a colourless crystal- 

 line body, melting at 41 and boiling at 182. With a little 

 water it liquefies, forming a fluid hydrate, which, however, is 

 only soluble in about 15 times its weight of water. 



Phenol is decidedly antiseptic, but recently doubts have 

 been expressed as to its disinfectant powers. Certain patho- 

 genic organisms are very resistant to phenol, e.g., the typhoid 

 bacillus can be separated from many other micro-organisms 

 by taking advantage of its power of growing in carbolised 

 nutrients.* 



Phenol is a violent plant poison, and a very dilute solution 

 will prevent the germination of seeds. It is sometimes used 

 as a weed destroyer. 



Many of the " disinfecting powders" of commerce consist 

 essentially of an indifferent powder, e.g., silicates or even silica, 

 containing about 15% of carbolic acid. They are often 

 coloured pink. Sometimes calcium sulphite is also present. 



Creasote or creosote is a mixture of cresol, C C H 4 (CH 3 )OH, 

 xylenol, C G H 8 (CH 3 ) 2 OH, and other higher members of the 

 series; about 1 or 2% of phenol is usually present. It is 

 colourless when fresh, bufc soon darkens. It possesses good 

 antiseptic powers and is thought to be preferable to phenol. 

 It is used in the preservation of timber. 



Many preparations containing cresols are in use as disin- 

 fectants. Lysol is obtained by mixing tar-oils (chiefly cresol) 

 with fat and saponifying with potash. It is soluble in water 

 and is apparently an excellent antiseptic. 



Jeycs' disinfectant and creolin also contain alkalies and 

 cresols. 



Izal is a reddish brown liquid, slightly heavier than water, 

 obtained in the process of coke manufacture in closed ovens. 

 It has antiseptic properties and, in strengths of 1 in 200, is a 

 good disinfectant. It has also been used with success as a 

 constituent of sheep dips. It has the advantage of being 

 non-volatile and therefore remains on the W T OO! for a long time. 



Wood creasote is a more powerful disinfectant than that from 

 coal tar. In addition to cresol and phenol it contains giiaiacol, 



* Rideal, Disinfection and Disinfectants, p. 151. 



