A. P. H. A. PHENOL COEFFICIENT 165 
making daily observations; (12) compare the killing times of the 
various solutions tested with that obtained from carbolic acid, and 
determine the carbolic coefficient of germicidal and penetrating powers 
combined. 
In tests with some common disinfectants and a seventy-two-hour 
incubation, there was no growth after one hour’s exposure to 4 per cent 
formalin; no growth after three hours’ exposure to 1 per cent formalin, or 
1 per cent corrosive sublimate solution; and no growth after five hours’ 
exposure to 5 per cent carbolic acid, 0.25 per cent formalin, and 10 per 
cent chloride of lime. Even after five hours’ exposure, however, there 
was growth with 1 per cent carbolic acid, 0.1 per cent corrosive subli- 
mate, 4 per cent chloride of lime, 2 per cent hyco, 1 per cent cresol, and 
2 per cent sulphonaphthol. 
TABLE XIX 
SHOWING COMBINED GERMICIDAL AND PENETRATING POWERS 
OF SOME *COMMON DISINFECTANTS 
(After Kendall and Edwards.) 
l fp 
Time of Exposure 
Disinfectants > Hution, | 
, 1 Hour. 3 Hours | 5 Hours. 
Carbolic acid ............. 0.000 5 + a _ 
Carbolic acid ...............00005 | 1 + + +} 
Formalin. ..........0.02: eee eee 4 — ~— 
Formalin. ............ 200 ee eee eee : 1 + — _ 
Formalin. 2.0.0.0... 0c cee ee ees 0.25 + + 
Mercuric chloride................. 0.1 + + _~ 
Mercurie chloride..... ..........-. 1.0 ++ _ _ 
Chloride of lime .. .... ......... 10.0 -+- + _— 
Chloride of lime...... ........... 4.0 + + +. 
Hyco... ee ce eee eee 2.0 +- + + 
Cresol.... 0... nee 1.0 + + + 
Sulphonaphthol. ...............- 2.0 + a + 
The American Public Health Association Standard Phenol Coeffi- 
cient. This association appointed a committee to report on the stand- 
ardization of disinfectants and the material given below is taken from 
that report as published in the American Journal of Public Health for 
July, 1918. 
Apparatus: Subculture Tubes. A test-tube rack of eight rows of 
ten holes each may be used for the subcultures. If the test be of 
