Alkalis — The hydroxyl ion (OH') inhibits or kills most bacteria and viruses 

 when the pH is greater than 9. The following alkalis can be used as disinfectants: 



1. Sodium hydroxide (NaOH): Commonly called caustic soda or lye, sodium 

 hydroxide is one of the most common alkalis used as a disinfectant. Its use as 

 a permitted disinfectant is recognized in 9 CFR part 71.10(a)(4), where these 

 instructions are given: "Sodium hydroxide (Lye) prepared in a fresh solution in 

 the proportion of not less than 1 pound avoirdupois of sodium hydroxide of not 

 less than 95 percent purity to 6 gallons of water, or one 13 1/2 ounce can to 5 

 gallons of water. Due to the extreme caustic nature of sodium hydroxide solution, 

 precautionary measurers such as the wearing of rubber gloves, boots, raincoat, and 

 goggles should be observed. An acid solution such as vinegar shall be kept readily 

 available in case any of the sodium hydroxide solution should come in contact 

 with the body." The proportions listed provide a working solution of 2 percent, 

 which is adequate for most disinfectant uses. Sodium hydroxide is not sporicidal 

 unless it is used at a concentration greater than 5 percent. This material is highly 

 caustic and must be used with extreme caution. WTien mixing, remember always 

 to add lye to water, not water to lye. 



2. Anhydrous sodium carbonate (Na^CO^): Known as soda ash, anhydrous sodium 

 carbonate is an effective cleaning agent. A 4-percent solution ( 1 lb in 3 gal water) 

 of anhydrous sodium carbonate is used for washing vehicles and is currently used 

 for cleaning the hooves of horses being imported into the United States. With the 

 addition of 0.1 -percent sodium silicate, 4-percent anhydrous sodium carbonate 



is the only disinfectant for use on aircraft. The requirements of 9 CFR part 91.41 

 give specific instructions for aircraft disinfection: "Prior to loading of animals, the 

 stowage area of aircraft to be used to export animals under the provisions of this 

 part shall, under the supervision of an inspector, be cleaned and then disinfected 

 using a freshly prepared solution of 4 percent sodium carbonate plus 0.1 percent 

 sodium silicate." 



3. Hydrated sodium carbonate (Na^CO^ • 10 H,0): Known as washing soda or 

 sal soda, hydrated sodium carbonate has 10 water molecules attached to each 

 molecule of sodium carbonate. To get the same level of disinfectant activity using 

 hydrated sodium carbonate would require roughly three times more dry product 

 than the amount of anhydrous sodium carbonate needed. 



4. Calcium hydroxide (CaOH): Calcium hydroxide, or air-slaked lime, has been 

 used as a disinfectant and is reasonably effective against many nonspore-forming 

 organisms. When mixed with water, CaOH forms hydroxyl ions and liberates heat 

 (CaO -i- H^O = Ca(OH), -i- heat). Although it is not sporicidal, it has been used to 

 disinfect premises. At a 20-percent suspension, it is commonly used as whitewash. 



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