FORMALDEHYDE UPON MICROFLORA OF MILK 213 



. REFERENCES 



JOHN F. ANDERSON and THOMAS B. McCLiNTic : I. Method of Standard- 



izing Disinfectants with and without Organic Matter. Hygienic 



Laboratory Bui. No, 82 (1912), pp. 1-20, 34, 73. 

 S. RIDEAL and E. K. RIDEAL: Some Remarks on the Rideal- Walker 



Test and the Rideal-Walker Method. Jour, of Infectious Diseases, 



Vol. X (1912), pp. 251-257. 

 H. C. HAMILTON and T. OHNO: Standardization of Disinfectants. 



Reprint No. 45 (1913), from Research Laboratory of Parke, 



Davis and Co., pp. 451-458. 

 - The Bacteriological Standardization of Disinfectants. Reprint 



No. 65 (1914), from Research Laboratory of Parke, Davis and Co. 

 M. L. HOLM and E. A. GARDNER: Formaldehyde Disinfection with 



Special Reference to the Comparative Value of Some of the 



Proprietary Products. Journal of Infectious Diseases, Vol. VII 



(1910), pp. 642, 643, 650, 658-659. 

 MARSHALL: Microbiology, pp. 173-180. 



EXERCISE 30. TO DETERMINE THE ACTION OF 

 FORMALDEHYDE UPON THE MICROFLORA OF 

 MILK 



Apparatus. Fresh milk, skim or whole; 1% solution of 

 formaldehyde; azolitmin solution; twelve sterile test tubes; 

 HoS04, concentrated commercial. 



Method. 1. Make the following mixtures in sterile 

 test tubes in plain milk, and duplicate in litmus milk (adding 

 2% azolitmin solution to the milk) : 



Milk. Formaldehyde 



9.0 c.c. + 1 c.c. ofl% =0.1% 



9.3 c.c. +0.7 c.c. of 1% =0.07% 



9.7 c.c. + 0.3 c.c. of 1% = 0.03% 



9.0 c.c. + 1 c.c. of 0.1% = 0.01% 



9.0 c.c. + 1 c.c. of 0.07% = 0.007% 



9.0 c.c. + 1 c.c. of 0.03% = 0.003% 



Place at room temperature. 



2. Record the action in each tube, the time required 

 for spoilage and the amount of formaldehyde necessary to 

 preserve the milk. 



