156 STERILIZATION AND DISINFECTION 
of a disinfectant may, for practical purposes, be defined as the figure 
that represents the ratio of the germicidal power of the disinfectant 
to the germicidal power of carbolic acid, both having been tested under 
the same conditions. 
TaBLE XIII 
Name “A.” 
Temperature of medication, 20° C. 
Culture used, B. typhosus, 24-hour, extract, broth, filtered. 
Proportion of culture and disinfectant, 0.1 ¢.c.+5 c.c¢. 
Time Culture Exposed to Action 
of Disinfectant for Minutes. Phenol 
Sample. Dilution. Coefficient. 
reticent | aerate | Sear | RINNE | Se RL | SETAE 
-|- 375 , 650 
- 80 "10 _ 
—|- 2 
Phenol............00+00eee 
—_ 
104) 
) 
= 
+++ 1 
++ 
++ 
. 4.69+5.91 _ 
Disinfectant “A ’’.......... 2 ~ 
— 
(eh) 
or 
© 
| 
| 
| 
5.30 
as 
t+tt++ttH+ i 
t+tt+H+tt 
++t+tis 
{ 
+++ | 
++I | 
Although the germicidal power of carbolic acid is taken as the unit 
of comparison, it is influenced to a certain extent by the conditions, par- 
ticularly the addition of organic matter, or, in other words, it is not 
a constant unit. This has to be borne in mind when making a com- 
parison of the relative values of the phenol coefficients of a disin- 
fectant determined with and without the addition of organic matter, 
respectively. It will readily be seen, for instance, that if the germi- 
cidal powers of a disinfectant and of carbolic acid were proportion- 
ately reduced by the addition of organic matter the coefficient of the 
disinfectant would remain unchanged regardless of whether or not 
organic matter was used. However, the germicidal power of car- 
bolic acid, like the other pure phenols, is, as compared with most 
other disinfectants, only slightly affected by the addition of organic 
