DISINFECTION 355 



agent, otherwise his work is likely to be of no avail. For 

 example, the use of carbolic acid as a protection against hog 

 cholera is of little or no value, since it is known that the 

 organism will live for months in the presence of one half 

 of one per cent, of this substance which is so effective in the 

 destruction of many disease-producing organisms. 



Each class of disinfectants has its advantages and dis- 

 advantages. A particular class can be used to advantage 

 under certain conditions, while, under other conditions, its 

 use may be of little value. 



Lime. In the manufacture of lime, the limestone, which 

 is ;i carbonate of lime, is heated to drive off the carbon- 

 dioxide. forming calcium oxide, which on exposure to the 

 air gradually combines, with the carbon-dioxide in the air 

 to form ilie carbonate again, or uir-xlaked lime. If the 

 quick or stone lime, as it is often called, is treated with six 

 parts of water to ten of lime, a dry white powder will be 

 obtained, called hydrate of lime or water-slaked lime. The 

 water-slaked lime resembles air-slaked lime in appearance, 

 but not in composition, as can be determined by placing a 

 lillle of each on tin- tongue. The air-slaked lime has a 

 chalky feel and taste, while the water-slaked causes the 

 tongue to burn. It has caustic and disinfecting properties, 

 while the air-slaked has no value whatever as a disinfectant. 



Lime is one of the best disinfectants that can be used on 

 the farm I'm- many purposes. The dry powder, produced 

 when a proper amount of water is added to the lime, can be 

 used or it can he applied to the walls and ceilings in the 

 form of whitewash. The whitewash has a germicidal ac- 

 tion, as well as a mechanical incrusting effect, thus placing 

 the organisms under such conditions that they can not exist 

 for any length of time. It makes the stables lighter and 

 cleaner than would otherwise be the case. If the white- 

 wash is prepared from good lime and properly applied, it 



