COAL TAR DISINFECTANTS 141 
Phenol and Cresol: 
CHs3 CHs CHs3 
(Now a OH 
|| | lor | | | 
\4 \Y \Z \4 
OH 
o-cresol m-cresol p~cresol phenol 
The action of these substances as disinfectants has been studied 
by Cooper (1912), who found that the entrance of the methyl and nitro 
groups increased the bactericidal and protein penetrating powers of 
phenol while the entrance of the hydroxyl group decreased these 
properties. Solutions of phenol in alcohol and in fat had no bactericidal 
action on spores and did not penetrate solutions of gelatin. The 
precipitating action of phenol is increased by adding acid. Cooper 
points out that the selective action of phenol on different bacteria 
is connected with the different susceptibilities of proteins to its pre- 
cipitating action. The absorption of phenol by bacteria is only the 
beginning of disinfection. No chemical union follows between the 
phenol and the bacterial protoplasm but it is associated with de-emul- 
sification of the collodial suspension as shown by the precipitation of 
proteins when a certain phenol concentration is reached. 
The superiority of m-cresol over phenol as a bactericide is due to 
the fact that cresol precipitates proteins in a lower concentration than 
phenol. Steenhauer (1916) showed that m-cresol is the strongest 
and p-cresol the next strongest disinfectant. The cresol solutions 
secured on the market are mixtures of the o-, m-, and p-cresols. The 
introduction of the methyl group has decreased the solubility. On 
account of this the cresols are often suspended in or mixed with some 
carrier. Both hard and soft soaps, for instance may be used. Lysol, 
a highly bactericidal substance, is prepared by saponifying linseed oil 
with commercial cresol in alcoholic solution. This is readily soluble 
in water and is used in from 2 to 5 per cent solutions. Weaker solu- 
tions must be used for disinfection of mucous membranes as the lining 
of the mouth and vagina. Steenhauer reported that m-cresol is the 
strongest bactericide with p-cresol next. He recommended the use 
of 5 per cent solutions. 
Thymol. This compound is probably of little value as a disin- 
fectant. Schmidt (1910) stated that thymol does not affect certain 
putrefactive bacteria and is not entirely efficient as an antiseptic in 
