Quote:
Originally Posted by hud 91gt
That doesn’t really make sense. As soon as some of it evaporates it brings the alcohol content down to the “desired” level, then it magically doesn’t dissolve? I’m betting it has more to do with health reasons or safety vs. it’s inability to kill germs.
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Google came up with this
https://blog.gotopac.com/2017/05/15/...-ipa-used-for/
"The presence of water is a crucial factor in destroying or inhibiting the growth of pathogenic microorganisms with isopropyl alcohol. Water acts as a catalyst and plays a key role in denaturing the proteins of vegetative cell membranes. 70% IPA solutions penetrate the cell wall more completely which permeates the entire cell, coagulates all proteins, and therefore the microorganism dies. Extra water content slows evaporation, therefore increasing surface contact time and enhancing effectiveness. Isopropyl alcohol concentrations over 91% coagulate proteins instantly. Consequently, a protective layer is created which protects other proteins from further coagulation.
Solutions > 91% IPA may kill some bacteria, but require longer contact times for disinfection, and enable spores to lie in a dormant state without being killed. A 50% isopropyl alcohol solution kills Staphylococcus Aureus in less than 10 seconds (pg. 238), yet a 90% solution with a contact time of over two hours is ineffective. Some disinfectants will kill spores with exposures times that exceed 3-12 hours, which are classified as chemical sterilants. So why do higher alcohol solutions yield fewer results for bactericidal and antimicrobial outcomes?"