PHENOL 639 



greater than that of pure phenol, with alkalies less. Light 

 tends to decompose it, but the efficiency is not affected. 

 It is poisonous and caustic. For practical uses its chief 

 value is as a standard, as its disinfectant value is com- 

 paratively low, and for spore-bearing organisms it is 

 practically useless. Like the cresols, its efficiency is 

 greatly increased by the addition up to saturation of 

 common salt or hydrochloric acid. The following results 

 well demonstrate the increased germicidal power of phenol 

 by additions of sodium chloride (Findlay, loc. cit.) : 



Anthrax spores treated. 

 Number of colonies develop- 



Solution ing after treatment (days). 



0137 



3 per cent, phenol .... 6300 1390 1260 950 

 3 + 1 per cent. NaCl . 5720 1450 1320 360 



3 + 8 per cent, NaCl . 1940 150 50 



Probably the addition of salt alters the distribution of the 

 phenol between the water and the cells, the salt increasing 

 the concentration of the phenol in the bacterial cells. 



" Crude carbolic acid " consists mainly of cresols and 

 higher phenols in proportions largely dependent on the 

 source of the tar from which they are prepared ; phenol 

 is nearly absent from it By themselves the cresols are 

 extremely insoluble in water ; in oil or alcohol they have 

 little or no disinfectant value. Cresols are much reduced in 

 efficiency by albuminoids. In saturated salt solution the dis- 

 infectant value of crude carbolic acid is greatly increased. 



Ordinarily neutral tar oils with no appreciable disin- 

 fectant value are left in, or mixed with, tar distillate, and 

 the saponified product produces an emulsion with water. 

 Innumerable products of this type are made. Their 

 efficiency varies not only with their active ingredients, but 

 also with the character of the emulsions which they form, 

 from about the same as that of phenol to about three times 



