COAGULATION COEFFICIENT 173 
The standard of comparison is the opacity produced in 5 c.c. of the 
1 per cent egg albumen solution when 5 c.c. cf 5 per cent phenol solu- 
tion is added (in a standard test tube of about 15 ¢.c. capacity). This 
phenol tube is placed against a black background. In making a test, 
varying dilutions of the disinfectant are added to the egg albumen 
solution until the opacity produced is the same as that in the phenol 
tube. In each test 5 c.c. of the dilution is added to 5 c.c. of the egg 
albumen in a standard test tube and the two tubes compared, placed 
against the black background. The following tentative procedure for 
making dilutions is suggested: 
DiLuTions oF DISINFECTANTS TO BE UsEp 
The phenol control solution (5 per cent) is made as for the Anderson- 
McClintic method of standardizing disinfectants, using only pure 
phenol crystals. 
Of the disinfectants to be tested 10 per cent and 1 per cent primary 
stock solutions are made; 10 per cent solutions of liquid disinfectants 
as alcohol, formalin, and acids, and 1 per cent solutions of the salts of 
heavy metals and of soluble substances generally. From these primary 
stock solutions the following secondary dilutions or sub-stock solutions 
are made, always in those amounts which will serve the purpose, that is, 
in amounts for perhaps ten sub-dilutions for each and every disinfectant 
to be tested: 
1/10 (of liquids only) 
1/100. 
1/1000 
1/10,000 
1/100,000. 
MeEtTHOD OF TESTING 
(a) Phenol Standard. Pour 5 c.c. of the egg albumen solution in a 
standard test tube, using a 5-c.c. pipette having a free outflow. Add 
to this 5 c.c. of the phenol stock solution (5 per cent). Set the tube 
in the standard test rack (with black background made of cardboard 
covered with black tissue paper). The degree of opacity developed is 
to serve as the standard of comparison. 
(b) Preliminary Testing. The albumen coagulating power of the 
disinfectant being unknown, much time and labor can be saved by 
testing with the four or five sub-stock solutions, adding 5 c.c. to 5 c.c. of 
