COAGULATION COEFFICIENT 171 
the subculture tubes are placed in the incubator and forty-eight hours 
later they are removed, read and recorded. 
Determining the Coefficient. The concentrations of the highest dilu- 
tions which gave negative results in five, ten, fifteen and twenty minutes, 
respectively, are divided by the corresponding concentrations of phenol 
to obtain a series of four coefficients. The arithmetical mean of the four 
is taken as the “ Mean Phenol Coefficient against Typhoid 20° C., 
five to twenty minutes, A. P. H. A.” It is recommended that a final 
report be based upon the results of not less than three separate tests. 
The coefficient will be known for brevity as the ‘‘ A. P. H. A. Standard 
Phenol Coefficient,” but for any other organism temperature, time 
ranges that may be employed the word “ Standard” will be omitted 
and the full expression given. The determination of these special 
coefficient for special uses is recommended. 
Determination of Coagulation Coefficient. (After Schneider, 1912). 
Certain chemicals which are used as disinfectants precipitate proteins 
and may be used up in that way. Mercuric chloride, for instance, is 
such a disinfectant and does not do its maximum work under such con- 
ditions. Many of the disinfectants do not coagulate albumin in the 
dilutions which are used for disinfecting. There seems to be no relation 
between the “ phenol” coefficient and the “ coagulating coefficient ”’ 
but it is often desirable to know just how active a certain substance ig 
in the precipitation of proteins. For this purpose Schneider (1912) 
devised the following procedure; 
ALBUMEN Trst SOLUTION 
Based upon the results of the preliminary experiments a 1 per cent 
aqueous (distilled water) solution of pure dried egg albumen is recom- 
mended as the substance upon which the different strength solutions 
of the various disinfectants is to act. 
The following methods for making the albumen solution are sub- 
mitted for consideration, hoping that other investigators may try them 
out comparatively: 
(a) Gravimetric Method A. Place 2 gms. of pure powdered egg 
albumen in 100 c.c. of boiled distilled water, shake and set aside for 
six to twelve hours, shaking frequently. Filter through a tared filter 
paper which has been dried (at 100° C.) to constant weight. Filtering 
is slow, requiring perhaps one-hour’s time. When the ‘last drop has 
filtered through, dry the filter paper with the unfiltered albumen residue 
upon it to constant weight and weigh. Deduct from this weight the 
