STANDARDIZATION OF DISINFECTANTS 255 



kept in mind that it is readily attacked by jmicrobes. However, 

 if carefully prepared with pure albumen, boiled distilled water, in 

 sterile vessels, and put on ice or in a cool place, it will keep for 

 perhaps 4 days. 



Any quantity of albumen solution may be made, it merely 

 being advised not to prepare more than may be required for the 

 tests contemplated. 



2. Gravimetric Method B. — In a dried and tared platinum dish 

 place 5 cc. of the albumen filtrate (2 grams in 100 cc. of boiled 

 distilled water), evaporate over water bath and dry to constant 

 weight, and from this determine the percentage of albumen in the 

 solution and the amount of water that must be added to the 

 albumen filtrate to make i per cent. 



The Phenol Standards 



The standard of comparison is the opacity produced in 5 

 cc. of the I per cent, egg albumen solution when 5 cc. of 5 per 

 cent, phenol solution are added (in a standard test-tube of about 15 

 cc. capacity). This phenol tube is placed against a black back- 

 ground. In making a test, varying dilutions of the disinfectant 

 are added to the egg albumen solutions in a series of test-tubes 

 until the opacity produced is the same as that in the phenol tube. 

 In each test 5 cc. of the dilution are added to 5 cc. of egg albumen 

 in a standard test-tube and the two tubes compared, placed against 

 a black background. 



Dilutions of Disinfectants to be Tested 



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 i per cent, 

 primary stock solutions are made; 10 per cent, solutions of Hquid 



