50 DESTRUCTION OF BACTERIA BY CHEMICALS 



and clothing after infectious diseases. Simple air disinfection 

 is of practically no value, since disease viruses do not live 

 long in the air but may settle upon surfaces where they can 

 be killed either by gaseous disinfectants or direct application 

 of germicides. All disinfection is rendered more efficacious 

 by a good cleansing and a liberal supply of "elbow grease." 



A chemical is tested for its antibacterial properties in 

 several ways, chief among which is the immersion of some of 

 the pure bacterial growth in solution of various strengths 

 of the chemicals. 



Some of the individual disinfectants are: 



Bichloride of Mercury (corrosive sublimate). This is 

 soluble in 16 parts of cold water. One part in 100,000 inhibits 

 the growth of most bacteria. In twice that strength many 

 kinds are killed in a few minutes. Spores are destroyed in 

 1 to 500 solution in water within one hour. In order to obtain 

 the best results with this corrosive sublimate it is necessary 

 to have an acid reaction, for which reason most of the tablets 

 now on the market are made up with an acid having no effect 

 upon the mercury salt. The acid reaction is especially 

 demanded when the material to be disinfected is pus, blood, 

 feces or the like, substances containing albumin which com- 

 bines with the mercury and renders it inert. It is wise to 

 use a strength of 1 to 500 for one-half hour when any such 

 organic material is present. The disadvantages of bichloride 

 are, beside that mentioned above, that it corrodes metals and 

 is rather hard on the skin. It is well to add some coloring 

 matter to the solution for the purpose of identification, since 

 this is a rapidly acting, corrosive, deadly poison. Great care 

 should be used in keeping the tablets and solutions, as many 

 accidents have occurred. Being odorless it attracts no 

 attention. 



Silver Nitrate. Park says that this salt has one-fourth 

 the value of the preceding as a disinfectant, but nearly the 

 same value in restraining bacterial growth. It is not a very 

 practical disinfectant, because of its destructive action on the 



