118 PRINCIPLES OF BACTERIOLOGY 





2. Strong Soda Solution. This, which is a stronger and more effective 

 cleansing solution and also a feeble disinfectant, is made by dissolving 

 one-half pound of common soda in three gallons, of hot water. The 

 solution thus obtained should be applied by scrubbing with a hard brush. 



When it becomes necessary to arrest putrefaction or to prevent the 

 spread of contagious diseases by surely killing the living germs which 

 cause them, more powerful agents must be employed than those re- 

 quired for simple cleanliness, and these are commonly called disin- 

 fectants. The following are some of the most reliable ones : 



3. Heat. Complete destruction by fire is an absolutely safe method 

 of disposing of infected articles of small value, but continued high 

 temperatures not as great as that of fire will destroy all forms of life; 

 thus, boiling or steaming in closed vessels for one-half hour will abso- 

 lutely destroy all disease germs. 



4. Carbolic Acid Solution. Dissolve six ounces of carbolic acid in 

 one gallon of hot water. This makes approximately a 5 per cent, solu- 

 tion of carbolic acid, which, for many purposes, may be diluted with 

 an equal quantity of water. The commercial ''soluble crude carbolic 

 acid " can be used instead of the pure carbolic acid for privies and 

 drains. It makes a white emulsion on account of its not entering 

 readily into solution. Care must be taken that the pure acid does 

 not come in contact with the skin. 



5. Bichloride Solution (bichloride of mercury or corrosive sublimate). 

 Dissolve sixty grains of pulverized corrosive sublimate and two table- 

 spoonfuls of common salt in one gallon of hot water. This solution, 

 which is approximately 1:1000, must be kept in glass, earthen, or 

 wooden vessels (not in metal vessels). For safety it is well to cover 

 the solution. 



The carbolic and bichloride solutions are very poisonous when taken 

 by the mouth, but are harmless when used externally. 



6. Milk of Lime. This mixture is made by adding one quart of dry, 

 freshly slaked lime to four or five quarts of water. (Lime is slaked by 

 pouring a small quantity of water on a lump of quicklime. The lime 

 becomes hot, crumbles, and as the slaking is completed a white powder 

 results. The powder is used to make milk of lime.) Air-slaked lime 

 (the carbonate) has no value as a disinfectant. 



7. Dry "Chloride of Lime." This must be fresh and kept in closed 

 vessels or packages. It should have the strong, pungent odor of chlorine. 



. Formalin. Add 1 part of formalin to 10 of water. This equals 

 in value the 5 per cent, carbolic acid solution. 



9. Creolin, tricresol, and lysof are of about the same value as pure 

 carbolic acid. 



The proprietary disinfectants, which are so often widely advertised 

 and whose composition is kept secret, are relatively expensive and 

 often unreliable and inefficient. It is important to remember that 

 substances which destroy or disguise bad odors are not necessarily 

 disinfectants, and that there are very few disinfectants that are not 

 poisonous when taken internally. 



