PHENOLOID SUBSTANCES 769 



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 developing 

 Solution. after treatment (days). 



1 3-7 



3 per cent, phenol .... 6,300 1,390 1,260 950 



3 + 1 per cent. NaCl 5,720 1,450 1,320 360 



3 + 8 per cent. NaCl 1,940 150 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 disinfectant 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 

 as much. Commercially they are known as soluble car- 

 bolic acid, soluble creosote, etc. Creolin is a type of 

 numerous preparations of the same character. They are 

 all poisonous and sensitive to albuminoids. If naphtha- 

 lene is present in excess it is deposited in cold weather on 



M.B. 49 



