248 STERILIZATION, ANTISEPSIS AND DISINFECTION 



injure metals or ordinary fabrics. The commercial solution con- 

 tains about 35 per cent, of formaldehyde, hence a 10 per cent, solu- 

 tion of "formalin" will contain but 3.5 per cent, of "formaldehyde," 

 which is, of course, the reactive substance. Formaldehyde is an 

 excellent disinfectant for sputum, urine and feces, and other excre- 

 tions; a 5 per cent, solution of formalin (corresponding to about 2 

 per cent, formaldehyde) in the proportion of two volumes of the disin- 

 fectant to one of the excretion will effect practical sterilization of 

 feces within an hour. Fomites are sterilized in the same manner. 

 The fumes are irritating, and disinfection should not be practiced 

 in the sick-room. 



Essential Oils. Essential oils have been used extensively in the 

 past, particularly in the treatment of nasal and pharyngeal infections, 

 and for mouth-washes. Menthol, thymol and eucalyptol, the active 

 principles of oil of peppermint, thyme and eucalyptus respectively, 

 undoubtedly possess antiseptic and feebly germicidal properties. 

 Cloves, cinnamon and other spices have been used for the preserva- 

 tion of certain types of foods; their efficiency probably depends largely 

 upon their content of essential oils. The expense of these substances 

 compared with their efficiency as antiseptics makes their use practically 

 prohibitive. 



Soaps. Cleanliness is a very important barrier to the spread of dis- 

 ease. Very few pathogenic bacteria upon exposed surfaces of rooms 

 can survive an application of hot soap suds applied with a vigorous 

 arm and a scrubbing brush. A 5 per cent, solution of washing soda 

 (commercial sodium carbonate) is even more efficient if applied hot, 

 but there are limitations to its use. Fine furnishings and hangings, 

 wall paper and similar objects cannot ordinarily be treated with liquid 

 disinfectants. 



Testing and Standardizing Liquid Disinfectants. The first satis- 

 factory method of comparing the disinfectant value of chemical disin- 

 fectants was that of Rideal and Walker, 1 widely known as the "Car- 

 bolic Coefficient" method. A modification of this method, proposed 

 by Anderson and McClintic, 2 is widely used in the United States. 

 Briefly, the method as modified by Anderson and McClintic consists 

 in comparing the activity of the unknown disinfectant solution in 

 various dilutions with a standard solution of carbolic acid; Bacillus 



1 Jour. Sanitary Institute, London, xxiv. 



2 Bull. Hyg. Lab., Washington, D. C., April, 1912, No. 82. Full details of method and 

 the disinfectant value of a large number of substances are given. 



