3. Virkon® S: Virkon S is a buffered peroxide compound with the addition of 

 surfactants and organic acids. In a 1 -percent solution, it has a pH of 2.6 and thus 

 would be effective as an acid disinfectant alone. The Material Safety Data Sheet 

 (MSDS) indicates that, in 1 -percent solution, Virkon S is nonirritating to skin 

 or eyes. No occupational exposure limit is specified on the MSDS. According to 

 company data, the 1 -percent solution has a 10-percent loss of initial activity after 

 7 days in 350 p/m hard water, and the powder form has a 2.3-percent loss of initial 

 activity after 36 months at 20 °C (68 °F). Packages of dipsticks are available to 

 check the strength of working solutions of this product. As a safety consideration, 

 Virkon S should not be subjected to high temperatures because, when the dry 

 form is heated to 70 °C ( 158 °F), it will decompose with evolution of sulfur dioxide 

 gas, which is toxic and irritating to skin and eyes and may be fatal if inhaled. 



Aldehydes — Aldehydes are chemical compounds of the general formula RCHO. 

 The R group may be aliphatic or aromatic. The aldehydes contain the carbonyl group 

 C==0. It is the carbonyl group that determines the chemistry of aldehydes. 



1. Formaldehyde (H-COH): A gas at room temperature, formaldehyde is used 

 as a gas and as a water solution called formalin. When used as a disinfectant, 

 formaldehyde is less efficacious in the presence of any organic matter. 

 Formaldehyde is sporicidal. 



2. Glutaraldehyde (CHO-CH -CH^-CH^-CHO): An oil at room temperature, 

 glutaraldehyde is stable at an acid pH and is "activated" before use by increasing 

 the pH to greater than 7 because the efficacy depends on the pH. To avoid 

 decomposition, do not make the pH greater than 9. Glutaraldehyde is sporicidal, 

 and organic matter has little effect on its disinfectant properties. 



Surfactants — Surfactants contain a molecule with a hydrophobic and a hydrophilic 

 region. The hydrophilic or polar region has an affinity for water. The hydrophobic or 

 hydrocarbon region is water repellent. 



1, Cationic surfactants: These include the quaternary ammonium compounds 

 (QAC). QAC are effective against gram-positive and gram-negative bacteria, 

 limited in their effectiveness against enveloped viruses, and ineffective against 

 the nonenveloped viruses. These compounds are not mycobactericidal and not 

 sporicidal, and even some bacteria such as Pseudomonas aeruginosa are not 

 susceptible to their action. The QAC are more effective when the pH of the 

 solution is greater than 7. The QAC are adversely affected by organic matter, and 

 their usefulness in the farm situation is limited. 



2. Anionic surfactants: These are strong detergents but weak disinfectants. 

 Examples include alkali-metal and metallic soaps as well as products such as 

 sodium laurel sulfate, which is found in many shampoos. 



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