208 Microbes and You 



HYDROLYSIS 

 When water is added to a substance, followed by a splitting of 

 the molecule, the reaction is called hydrolysis. Concentrated 

 acids and alkalies, and hot water exert some of their disinfecting 

 power through this means. 



FORMATION OF SALTS WITH PROTEINS 

 Certain heavy metals, including mercury and silver, act as good 

 disinfectants when their salts come in contact with microorganisms. 

 The salts combine directly with the protein of the organisms, 

 throwing the protoplasm out of balance, and causing the eventual 

 death of the organism. The halogens kill bacteria by a direct 

 combination with the protein, although other chemical reactions 

 also play a part in the disinfecting process. 



COAGULATION OF CELLULAR PROTEIN 

 Treatment of orcranisms with disinfectants often results in the 

 coagulation of the colloidal protoplasm. This severe physical and 

 chemical shock kills microbes. 



While other chemical responses may be offered to explain dis- 

 infection, the four reactions briefly touched upon above probably 

 include the more important changes involved in this lethal process. 



METHODS OF EVALUATING AND STANDARDIZING 

 DISINFECTANTS 



The general public is usually impressed bv "scientific claims" 

 in support of product "A" in preference to product "B." If this 

 were not so, advertising would not base its success in selling cam- 

 paigns on these laboratory findings. To one who has never had 

 the advantage of an exposure to courses in science, the half-truths 

 of some advertising have a strong appeal. There mav be nothing 

 wrong in the claims as far as they go, but an informed person 

 should take time out to ask himself a few questions about what has 

 not been said in the advertisements. 



The importance of conducting uniform tests for evaluating 



