Why is 70% isopropyl alcohol a better disinfectant than 99% isopropanol?(blog.gotopac.com)
blog.gotopac.com
Why is 70% isopropyl alcohol a better disinfectant than 99% isopropanol?
https://blog.gotopac.com/2017/05/15/why-is-70-isopropyl-alcohol-ipa-a-better-disinfectant-than-99-isopropanol-and-what-is-ipa-used-for/
137 comments
Thank you, I immediately hit back when I saw how long that article was.
The second sub-heading asks the question, and answers it in the first paragraph, so you can gain the answer without reading the entire article; if it grips you, then you can keep reading.
I relate with you. I wish articles also published a TLDR version.
Personally, I've trouble focusing if the content is less engaging, or am there just to know the gist. I suspect I've ADD-like traits - when I see an article beginning like "it was a warm sunny day in...", I say, "OK, maybe later". I however do appreciate long read articles have their place.
So far I've noticed only Business Insider does this on their articles.
Personally, I've trouble focusing if the content is less engaging, or am there just to know the gist. I suspect I've ADD-like traits - when I see an article beginning like "it was a warm sunny day in...", I say, "OK, maybe later". I however do appreciate long read articles have their place.
So far I've noticed only Business Insider does this on their articles.
« It was a warm sunny day in... » and i saw your comment on ADD, i was thinking it’s not really how or it works. It’s that you can’t focus on what your are reading. You start thinking about something else while reading and you don’t even notice it. « ...the end. » damn it. Let’s read it again « It was a warm sunny day in... » and I’m telling you it’s the worst thing ever because you can’t control it, no matter how hard you tell yourself I need to focus on it. It’s not a conscious decision to procrastinate. « ... the end. » Shit, again?
At least that’s how it is for me.
At least that’s how it is for me.
The explanation I was always given when taking my biohazard/biosafety courses was that concentrations of EtOH or IPA greater than 70% evaporated too quickly to have the contact time you needed to sterilize e.g. work surfaces or (even worse) your gloved hand.
Apparently here they mention that higher conc. of water make it a better solvent... which I buy, but alcohols still aren't the worst solvent for e.g. hydrophillic membranes, so I think other factors like contact time are likely in play.
Apparently here they mention that higher conc. of water make it a better solvent... which I buy, but alcohols still aren't the worst solvent for e.g. hydrophillic membranes, so I think other factors like contact time are likely in play.
The interesting one is solutions >91% - they kill cells immediately- but this coagulates the cell proteins forming a protective layer - dropping time to disinfect from ten seconds to over two hours.
It's fascinating how deep one can dive in any subject and still produce useful actionable insights :-)
It's fascinating how deep one can dive in any subject and still produce useful actionable insights :-)
Yea, I mean that is crucial information for using the product. You would think they would explain some of this on the bottle.
Can someone link to a study that shows this is the case for virusses also?
The example listed in the article, Staphylococcus Aureus, is a species of bacteria.
Last time I had this discussion they linked to a study that said that for viruses, higher concentrations are better.
(Epidemiologic Background of Hand Hygiene and Evaluation of the Most Important Agents for Scrubs and Rubs Günter Kampf and Axel Kramer)
The example listed in the article, Staphylococcus Aureus, is a species of bacteria.
Last time I had this discussion they linked to a study that said that for viruses, higher concentrations are better.
(Epidemiologic Background of Hand Hygiene and Evaluation of the Most Important Agents for Scrubs and Rubs Günter Kampf and Axel Kramer)
Likely depends on the type of virus. There are two types, enveloped and non enveloped. The enveloped would likely act similar to bacteria whereas the non-enveloped would likely suffer more from higher concentrations of alcohol.
And the coronavirus is enveloped. https://theconversation.com/vodka-wont-protect-you-from-coro...
and soap is both sufficient and great at destroying the coronavirus. https://www.engineering.com/DesignerEdge/DesignerEdgeArticle...
Do you happen to know of any peer-reviewed sources stating this? Up to now I've not been able to find any.
Since we're talking about counterintuitive things related to the coronavirus crisis, I was surprised to learn that N95 masks, that remove 95% of particles of size 0.3 μm, are even more efficient with smaller particle sizes. In turns out that 0.3 μm is the hardest particle size to filter--they call it the most penetrating particle size--hence filter testing is done at this worst-case size. The reason is that filters work due to several mechanisms which dominate at different particle sizes according to a curve:
"For very small particles, less than 0.1 μm in diameter, the primary filtration mechanism is diffusion and the filter is very efficient. For particles between approximately 0.1 and 0.4 μm the filter is less efficient as the particles are too large for a great diffusion effect and too small for a large interception effect. Particles above approximately 0.4 μm enter the region where interception along with inertial impaction are predominant and the filter is very efficient again."[1]
So if your filter is 95% efficient at 0.3 μm, it's even better at bigger and smaller sizes. The SARS-CoV-2 virus is 0.05 to 0.2 μm in diameter, so an N95 mask will be substantially better than 95% for coronavirus.
[1] https://www.tsi.com/getmedia/4982cf03-ea99-4d0f-a660-42b24ae...
"For very small particles, less than 0.1 μm in diameter, the primary filtration mechanism is diffusion and the filter is very efficient. For particles between approximately 0.1 and 0.4 μm the filter is less efficient as the particles are too large for a great diffusion effect and too small for a large interception effect. Particles above approximately 0.4 μm enter the region where interception along with inertial impaction are predominant and the filter is very efficient again."[1]
So if your filter is 95% efficient at 0.3 μm, it's even better at bigger and smaller sizes. The SARS-CoV-2 virus is 0.05 to 0.2 μm in diameter, so an N95 mask will be substantially better than 95% for coronavirus.
[1] https://www.tsi.com/getmedia/4982cf03-ea99-4d0f-a660-42b24ae...
> So if your filter is 95% efficient at 0.3 μm, it's even better at bigger and smaller sizes. The SARS-CoV-2 virus is 0.05 to 0.2 μm in diameter, so an N95 mask will be substantially better than 95% for coronavirus.
small nit. the corona virus gloms onto other particles of differing sizes in an aerosol though it's not super clear what size they are.
> The size of infective airborne viral particles is not well known and the aerosol transmission of viral diseases is currently debated in the literature (Roy and Milton, 2004; Tellier, 2006).
https://academic.oup.com/annweh/article/52/3/177/312528
small nit. the corona virus gloms onto other particles of differing sizes in an aerosol though it's not super clear what size they are.
> The size of infective airborne viral particles is not well known and the aerosol transmission of viral diseases is currently debated in the literature (Roy and Milton, 2004; Tellier, 2006).
https://academic.oup.com/annweh/article/52/3/177/312528
Same reason that we care about the concentration of PM2.5 particles in the atmosphere. Once we inhale them they manage to reach the very end of our lungs.
Is it? That's different from the counterintuitive N95 filtration efficacy. PM2.5 designates particles of diameter 2.5 microns and smaller, and I've read nothing that implies particles smaller than 2.5 microns are somehow easier for the respiratory tract to keep out of the lungs. The graph of filtration efficacy as a function of particle size is U-shaped for N95 masks, but not for the human respiratory tract.
You might find it interesting to know too that HEPA filters get more effective as they approach end-of-life.
So is the only reason to change filters to avoid blockage and reduced airflow but not filtering capacity?
I think they can also collect enough organic matter for mold to start growing on the downstream side. I base that on pictures of automotive cabin filters that are revolting.
Would some generous Lysol spray get rid of the mold?
Yes, but it will ruin dust filtration, so the proper choice is hot water vapor, dry heat, or hydrogen peroxide. Perhaps silver ions too.
HEPA filters use exactly the same meltblown fabrics as respirators, except thicker and in accordion form.
HEPA filters use exactly the same meltblown fabrics as respirators, except thicker and in accordion form.
Just flip it around
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For a more observable example, think about sorting American coins.
A dime is the easiest because it is the smallest. Quarters are much larger so are also easy. In the middle are pennies and nickels which are the hardest to separate from one another because they're so close in size.
Here's a video that demonstrates it: https://www.teachengineering.org/activities/view/cub_coinsor...
A dime is the easiest because it is the smallest. Quarters are much larger so are also easy. In the middle are pennies and nickels which are the hardest to separate from one another because they're so close in size.
Here's a video that demonstrates it: https://www.teachengineering.org/activities/view/cub_coinsor...
Since a filter sorts particles from air molecules, this would imply that the hardest particles to filter are just a couple atoms large.
To be fair, that’s probably true. It’s just that the particles at that scale are other molecules and they are indeed very hard to filter out mechanically.
If I have a 91% currently, can I just add water to dilute it? Do I need some kind of special water vs what’s from my tap?
Diluting Down 99% IPA to the desired concentration: A Lesson in Math & Chemistry
https://onsenlabs.com/blogs/blog/isopropyl-alcohol-ipa-aka-i...
Also includes a dilution table for 91%.
https://onsenlabs.com/blogs/blog/isopropyl-alcohol-ipa-aka-i...
Also includes a dilution table for 91%.
Their table seems reasonable, but the first example they work through is wrong.
>Example 1:
>Suppose a scientist has a bottle of 99% IPA (C1) that they want to dilute down to 70% (C2). To end with 50mL of 70% IPA (V2), how much volume of 99% IPA should they use and dilute with distilled water to create the final solution?
>99% x V1 = 70% x 50mL = 35.35mL
>Thus, adding 35.35mL of distilled water to 14.65mL of 99% IPA creates a 50mL solution of 70% IPA.
(They reversed the water and IPA quantities.)
>Example 1:
>Suppose a scientist has a bottle of 99% IPA (C1) that they want to dilute down to 70% (C2). To end with 50mL of 70% IPA (V2), how much volume of 99% IPA should they use and dilute with distilled water to create the final solution?
>99% x V1 = 70% x 50mL = 35.35mL
>Thus, adding 35.35mL of distilled water to 14.65mL of 99% IPA creates a 50mL solution of 70% IPA.
(They reversed the water and IPA quantities.)
The table's garbage. It's showing the total volume as exactly equal to water volume plus alcohol volume, out to four digits. That's not how it works. A mixture of water and alcohol (whether ethanol or isopropyl) gets more compact because the different molecules can pack together better, by up to a few percent.
Is it inaccurate enough that it cannot be used to safely create disinfectant-grade 70% dilutions from 99% or 91%?
If you're measuring things by slopping them into a measuring cup instead of weighing them out to the milligram, you'll never know the difference.
It won't matter for "eh somewhere between 55% and 75% is fine", but if you have a good measuring cup you could easily see the difference in volume.
I don't know why the chart assumes you're measuring down to thirds of milligrams, though...
I don't know why the chart assumes you're measuring down to thirds of milligrams, though...
Good catch!
That didn’t answer my question about what kind of water to use.
Tap water will be fine. The alcohol you're diluting will disinfect it.
If you want to be ultra-sure, then use distilled. But be aware it's also bought by people who use it for their CPAP machines, so don't go nuts.
If you want to be ultra-sure, then use distilled. But be aware it's also bought by people who use it for their CPAP machines, so don't go nuts.
It depends on where you are; my tap water has extremely high mineral (>40 gpg) content, and I could definitely see that interfering with its disinfectant properties (not to mention leaving a residue behind).
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It repeatedly says "distilled water."
"… we find that they would need to add 3.31 ounces of (distilled) water with 8 ounces of 99% IPA …"
"… we find that they would need to add 3.31 ounces of (distilled) water with 8 ounces of 99% IPA …"
Frankly I don't think it matters at all. Consider if you wipe down a surface with 70% IPA it'll dissolve all sorts of crud.
It’s preferable to used sterile distilled water or water that has been boiled according to the WHO.
https://www.who.int/gpsc/5may/Guide_to_Local_Production.pdf
https://www.who.int/gpsc/5may/Guide_to_Local_Production.pdf
Thank you!
Yes. Just dilute it in the correct ratio to bring it to the required concentration. The purity of the water is not particularly important. (If it's drinkable, it's perfectly OK to use. Go ahead and use tap water if you want.)
The formula is simple: 'Concentration Required' divided by 'Concentration Supplied' multiplied by 'Final quantity Required'. That will give you the amount of 91% isopropyl alcohol you need to measure out, then dilute to the 'Final quantity required' with your tap water. (Or better still, use Distilled Water or De-Ionized Water.)
So: You want 500 mls of isopropyl alcohol 70% and you have isopropyl alcohol 91% on hand -
Dilute that 384.6 mls to 500 mls with water and there's your 500 mls of isopropyl alcohol 70%.
Of course, you don't need to be quite so finicky when it comes to biological measurements. You'd round off the 384.6 mls to 385 mls (or even 380 mls or 390 mls) without any appreciable loss of effectiveness.
The formula is simple: 'Concentration Required' divided by 'Concentration Supplied' multiplied by 'Final quantity Required'. That will give you the amount of 91% isopropyl alcohol you need to measure out, then dilute to the 'Final quantity required' with your tap water. (Or better still, use Distilled Water or De-Ionized Water.)
So: You want 500 mls of isopropyl alcohol 70% and you have isopropyl alcohol 91% on hand -
Concentration required = 70%
Concentration Supplied = 91%
Final quantity required = 500 mls
Dilute that 384.6 mls to 500 mls with water and there's your 500 mls of isopropyl alcohol 70%.
Of course, you don't need to be quite so finicky when it comes to biological measurements. You'd round off the 384.6 mls to 385 mls (or even 380 mls or 390 mls) without any appreciable loss of effectiveness.
If you mix cheap booze (e.g. 40% vodka) with 91% isopropyl, you can make a larger quantity of 70% sanitizer than you could with pure water.
Mixing on a scale can be pretty confusing, though, because the percentages are (I think) by volume, and water and alcohol have different densities.
Mixing on a scale can be pretty confusing, though, because the percentages are (I think) by volume, and water and alcohol have different densities.
It can also be confusing if you check the volumes after mixing, since the water-alcohol interaction decreases the molecular spacing and the total volume. V_(water + alcohol) < V_water + V_alcohol.
https://en.wikipedia.org/wiki/Alcohol_by_volume#Volume_chang...
https://en.wikipedia.org/wiki/Alcohol_by_volume#Volume_chang...
Any booze you buy has a huge tax on it, so you would be better of, with cleaning alcohol.
Normally, yes. Today, I’m not even able to find isopropyl at many stores. I’m actually thinking about ordering flux cleaner for my soldering, for the first time in my life.
You can get methanol pure and cheap from auto stores (in regions that get cold, anyway). Just try not to get it on your skin or breath the fumes too much. It's quite a bit more toxic. Definitely don't use it to make hand sanitizer.
And also ethanol vs isopropanal, might add a bit of complexity
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Not being able to clean my electronics from flux has been a collateral damage of Covid-19.
I wish this article was more popular so people would stop hoarding 99% isopropyl.
I wish this article was more popular so people would stop hoarding 99% isopropyl.
99% from electronics supply houses has been the only IPA available for a while. Newark had it in stock the other day, I bought some for my electronics work. The wife borrowed half a bottle to make her sanitizer with though lol.
I had more luck going to a small rural town
that's what I have been doing. I live in Dallas and head an hour or so East for items I know are going to be out of stock locally.
One downside is that they dont take as much precautions in my experience.... Almost none had masks for example.
At work, we already use technical grade 99.8+% IPA for various things and have a bunch on hand. so we have been prep'ing 70% with RO water and wiping down high touch surfaces.
70% IPA in water is the go-to cleaning/sanitizing agent for most pharmaceutical cleanrooms. They also use other agents, 0.2-0.5% bleach, low pH cleaners, peroxides, etc... but IPa is the mainstay.
70% IPA in water is the go-to cleaning/sanitizing agent for most pharmaceutical cleanrooms. They also use other agents, 0.2-0.5% bleach, low pH cleaners, peroxides, etc... but IPa is the mainstay.
Why water is so "sticky" is a very interesting subject
https://www.exploratorium.edu/ronh/bubbles/sticky_water.html
I think our personal every day experience with water dulls the intrigue around one of the more remarkable and unique substances on the planet.
My favorite is Ultrapure Water (UPW) [0]. It's so pure, that it is used a a stringent. I watched video about one of those underground subatomic particle experiments where they use UPW. One of the technicians accidentally let his hair get wet, and it immediately "bleached" his hair.
[0]https://en.wikipedia.org/wiki/Ultrapure_water
[0]https://en.wikipedia.org/wiki/Ultrapure_water
Stringent just means something is strict, as in the standards for making UPW. Nothing is “used as a stringent.”
UPW also doesn’t immediately bleach hair, it would have to be a pretty prolonged heavy stream. Mostly UPW is pain in the ass because it corrodes metallic pipes, but is pretty harmless to people unless you really have massive amounts. One of the reasons it’s harmless is because the moment it touches you it isn’t really ultra pure anymore, it really takes parts per million to become not UPW.
UPW also doesn’t immediately bleach hair, it would have to be a pretty prolonged heavy stream. Mostly UPW is pain in the ass because it corrodes metallic pipes, but is pretty harmless to people unless you really have massive amounts. One of the reasons it’s harmless is because the moment it touches you it isn’t really ultra pure anymore, it really takes parts per million to become not UPW.
I think he meant an https://en.wikipedia.org/wiki/Astringent .
Didn't know the word, thanks!!
I don’t understand why it would bleach the hair? Theoretically couldn’t you drink this? It’s just water that’s free of contaminates like viruses, bacteria, etc?
Ultra pure water generates a very strong osmotic gradient in that it will simultaneously explode cells as the pure water rushes in to reduce particle count inside a cell while at the same time drawing out any free particles.
Another way to think about it is that UPW is an acid with a concentration of 55 Moles/liter.
Another way to think about it is that UPW is an acid with a concentration of 55 Moles/liter.
Also, why does alcohol easily kill microorganisms but doesn't destroy skin cells?
outer skins cells are already dead....
Also, alcohol will certainly leave your hands dry and cracked given prolonged contact.
(I used to refurbish old PCs and we used isopropyl alcohol liberally as a cleaner.)
(I used to refurbish old PCs and we used isopropyl alcohol liberally as a cleaner.)
> Also, alcohol will certainly leave your hands dry and cracked given prolonged contact.
Indeed, alcohol will dry the hell out of the skin, which is why alcoholic hand sanitiser have some sort of moisturiser included (e.g. glycerol).
Indeed, alcohol will dry the hell out of the skin, which is why alcoholic hand sanitiser have some sort of moisturiser included (e.g. glycerol).
Even with the moisturizer, hand sanitizer will cause my knuckles to become so chapped they cracked and bled within a few days with just a few applications per day. I had to stop using it as I began to fear infection.
Yes, the moisturiser mitigates the issue but will not solve it. If you need to sanitise your hands a lot and they’re sensitive you may want to use or switch to disposable gloves.
Or a well chosen brand of non-disposable gloves that survive disinfection with it well. Nitrile and butyl don't and are good for incidental contact only, they will swell; latex, vinyl, thick PET and norprene do work for more extended time. You have to be thorough in rubbing so mechanical resistance to that could be important too, making norprene the material of choice closely followed by PET.
(The latter three depend on the brand, some might start to slowly dissolve or harden after many applications due to plasticizer leaching. Always check with manufacturer.)
(The latter three depend on the brand, some might start to slowly dissolve or harden after many applications due to plasticizer leaching. Always check with manufacturer.)
And sanitizers are usually mostly ethyl alcohol, for the same reason.
In the 80's they started making alcohol based sun screen. I thought the stuff was great! Yeah not great. I'll still use it but only for one day. Otherwise I use the greasy stuff.
Never tried it so am curious why youd use it but only for one day. Does it dry the skin badly after more than one use?
That was my experience. Using it multiple days in a row trashes my skin.
This is one reason commercial hand sanitizers are [usually] made predominantly of ethyl alcohol, with a small amount of water and IPA added in. Ethyl alcohol does not dry out your skin nearly as much.
Wow... I used to watch a youtuber clean his tools with a bottle labeled as "Isopropyl Alcohol, AKA IPA" I always thought he was making fun of IPAs as in the beer style. I feel so dumb hahaha x_x
My theory is that three-letter acronyms are so popular because they are strike a balance between length and ambiguity. I.e. two-letter acronyms are too ambiguous, but four-letter acronyms are too long for the uniqueness benefit.
Most of the remaining ambiguity of three-letter acronyms could be avoided if people didn't get upset about redundant acronym expansion: "I cleaned with IPA alcohol after having an IPA ale."
[1] RAS syndrome: https://en.wikipedia.org/wiki/RAS_syndrome
Most of the remaining ambiguity of three-letter acronyms could be avoided if people didn't get upset about redundant acronym expansion: "I cleaned with IPA alcohol after having an IPA ale."
[1] RAS syndrome: https://en.wikipedia.org/wiki/RAS_syndrome
Most people don't care about RAS syndrome, except semi-intelligent people who think grasping at (incorrect) pedantry proves they are smart.
Depends on the acronym for me.
ATM Machine grates on my sensibilities, since we all know what an ATM is and calling it a "machine" is both redundant and low-information. It's like calling an ATV an ATV vehicle (which I have never heard): would you call a truck a truck vehicle?
PIN number on the other hand, I'm fine with. A pin is a small piece of steel used in sewing, a PIN number is a number you type into an ATM.
ATM Machine grates on my sensibilities, since we all know what an ATM is and calling it a "machine" is both redundant and low-information. It's like calling an ATV an ATV vehicle (which I have never heard): would you call a truck a truck vehicle?
PIN number on the other hand, I'm fine with. A pin is a small piece of steel used in sewing, a PIN number is a number you type into an ATM.
I think people stop parsing ATM as an acronym and start parsing it as just the name of a thing. Which is understandable. When I see ATM I dont think ... I just realized I forgot what the A and T stand for. Apparently automated teller? Perfect example I guess. As far as I'm concerned, ATM is just the name of the thing. And I parse it as such, so ATM machine isn't redundant since ATM doesnt point to "automated teller machine" in my mind. It just points to "ATM."
I also find misuses of RAS syndrome fun. AAV vector isn't RAS syndrome. It stands for adeno associated virus vector. But people are eager to jump on whatever pedantry they think they can find, makes them feel smart I guess.
I also find misuses of RAS syndrome fun. AAV vector isn't RAS syndrome. It stands for adeno associated virus vector. But people are eager to jump on whatever pedantry they think they can find, makes them feel smart I guess.
I don't know that it's even RAS syndrome.
Some machines have 'machine' in their name, most don't. A milling machine, yes, but who says lathe machine?
ATM machine just sounds weird to me. The fact that the "M" stands for machine doesn't help but it's not decisive.
That's what I mean by redundant: it's like saying spoon utensil.
Some machines have 'machine' in their name, most don't. A milling machine, yes, but who says lathe machine?
ATM machine just sounds weird to me. The fact that the "M" stands for machine doesn't help but it's not decisive.
That's what I mean by redundant: it's like saying spoon utensil.
But for me ATM is like milling, it's a machine that has machine in its name. It's not like lathe, probably because I've grown up surrounded by people that call it an atm machine. You cant fight language after a point - there's a point where double negatives are grammatically incorrect, and there's a point where we are at now where wikipedia just classifies some dialects of english as having negative concord, where multiple negatives affirm (instead of contradict) eachother. Same way, at a point it probably makes more sense to talk about redundant acronyms as just a thing english does than try and say that a construction that a lot of people use and that everyone can understand is a grammatically incorrect thing. So ATM vs ATM machine becomes a dialect choice rather than some grammatical discussion, like British vs English spelling
That's a bunch of BS shit! ;)
Wait until you hear about International Phonetic Alphabet.
We need to expand the TLA space.
The only options I can think of are increasIng the number of letters and redefining “T” to “tetra” or even “thirty”.
Time to get started on a new RFC
The only options I can think of are increasIng the number of letters and redefining “T” to “tetra” or even “thirty”.
Time to get started on a new RFC
ETLAs got you covered:
https://wiki.c2.com/?ExtendedThreeLetterAcronym
Although I'd like to see something like XTLAs, for eXtensible Three Letter Acronyms.
https://wiki.c2.com/?ExtendedThreeLetterAcronym
Although I'd like to see something like XTLAs, for eXtensible Three Letter Acronyms.
You can never have too many The Last Airbender spinoffs.
I guess I'm still not getting TLA, since my Temporal Logic of Actions model says there should only be 17 valid spinoff states.
Perhaps consider a FLAX?
Four letter acronym, experimental.
Four letter acronym, experimental.
That will only work until the RFC is approved, at which time the X will be dropped.
I wonder if they call this passivation like they do in chemistry - https://youtu.be/2yE7v4wkuZU?t=394
And here I thought the 'acid to water' rule was only so you would have water splashing instead of acid. TIL (and I was a chemistry undergrad)
What do you mean? How does the order of adding ingredients influence passivation?
You should create an acid water mixture before adding the mixture to another chemical.
You should create an acid water mixture before adding the mixture to another chemical.
"Do what you oughta, alway add acid to water" instead of water to acid is a safety mantra taught in high school and undergrad chemistry labs. You are correct but if you add the water to acid in the situation they'd shown the acid would be too concentrated as well.
If you feel dumb it means you're learning
For me, the site only shows a multi-step hCaptcha. I solved it the first time, then the page reloaded and showed me the second one, which after two puzzles told me to try again.
My understanding is that soap and water is even better for coronavirus. Not just to wash it away, but to actually destroy is because it has a very fragile lipid layer.
It’s not even better. Washing with soap and water is effective but rubbing alcohol (Both 70% and 99%) takes seconds to kill coronavirus. It is almost instantaneous in terms of effectiveness. Soap and water take a few mins to reach the same level of effect as rubbing alcohol.
There was a recent study by Stanford that measured the effectiveness of various cleaning methods.
There was a recent study by Stanford that measured the effectiveness of various cleaning methods.
That's not what I get from these articles, which say it takes 30 seconds for alcohol to kill it (on surfaces), while soap and water (with scrubbing) will do the trick with 20 seconds.
https://www.uchealth.org/today/why-soap-and-water-work-bette...
https://www.uchealth.org/today/ins-and-outs-of-disinfecting-...
https://www.marketwatch.com/story/deadly-viruses-are-no-matc...
If you've got a better reference I'd be interested in seeing it, but this is what I've found.
https://www.uchealth.org/today/why-soap-and-water-work-bette...
https://www.uchealth.org/today/ins-and-outs-of-disinfecting-...
https://www.marketwatch.com/story/deadly-viruses-are-no-matc...
If you've got a better reference I'd be interested in seeing it, but this is what I've found.
https://www.thelancet.com/cms/10.1016/S2666-5247(20)30003-3/...
Table C lists the various disinfectants they tried including ethanol at 70%. All of them found undetectable levels of SARS-CoV-2 after 5 mins except hand soap, which took between 5 mins and 15 mins.
I was off in my recollection that the study showed that alcohol killed the virus immediately. I may have confused that with a press conference several weeks ago but that data is probably suspect. All we know is that within 5 mins alcohol killed it to undetectable levels.
Also note that the 20 second rule has never been tested. There is some value in washing in a sink with running water since it is physically removing the virus off your hands. And it’s been socialized that is will work in general for bacteria but no one has actually tested to see if 20 seconds of hand washing with soap will clean you of coronavirus specifically. The study above actually tested for coronavirus although I don’t think the soap test was for running water.
Table C lists the various disinfectants they tried including ethanol at 70%. All of them found undetectable levels of SARS-CoV-2 after 5 mins except hand soap, which took between 5 mins and 15 mins.
I was off in my recollection that the study showed that alcohol killed the virus immediately. I may have confused that with a press conference several weeks ago but that data is probably suspect. All we know is that within 5 mins alcohol killed it to undetectable levels.
Also note that the 20 second rule has never been tested. There is some value in washing in a sink with running water since it is physically removing the virus off your hands. And it’s been socialized that is will work in general for bacteria but no one has actually tested to see if 20 seconds of hand washing with soap will clean you of coronavirus specifically. The study above actually tested for coronavirus although I don’t think the soap test was for running water.
This link is not at all working for me (brings up the Lancet site with no content). Is it possible to get a link to the actual file?
Interesting thanks for the link.
Per the article, which seems thorough & authoritative, calling 73%-100% isopropyl alcohol solutions ‘rubbing alcohol’ is a misnomer. (This was news to me, but seems a precision important to respect when making hygienic recommendations.)
What does it mean for viruses?
Covid-19 is number one issue...then let's work down.
This matters because we need to keep it simple. If you run around telling people 99% is bad for C19 when it isn't, you are ruining peoples solutions when you don't have to.
Sorry but these factoids are the fking issue. Telling people soap is better when hand sanitizer is clearly a better real world solution has caused lots of issues.
Does 99% work worse on a virus like C19 by a significant amount?
Covid-19 is number one issue...then let's work down.
This matters because we need to keep it simple. If you run around telling people 99% is bad for C19 when it isn't, you are ruining peoples solutions when you don't have to.
Sorry but these factoids are the fking issue. Telling people soap is better when hand sanitizer is clearly a better real world solution has caused lots of issues.
Does 99% work worse on a virus like C19 by a significant amount?
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I’m working on a nebulized ethyl alcohol biocidal therapy for SARS-CoV-2 and had to research this (plz see my Twitter for a chronology @jhazani). I’m disappointed the link abstracts the actual mechanism of action, other than a hypothesis that evaporation time and contact time makes a difference. It still does not explain distinctly the effects of contact time, which principally involves the polarity of alcohol which disrupts the viral envelope and “denatures” proteins according to the CDC [1] and their arcane reference text you can only find in a medical school library [2].
In other words, the hypothesis is there is electrostatic attractive forces that rip the buggers apart, in which this “pressure” is quantitatively stronger in the presence of molecular hydrogen bonding, ie greater dipole moments between the aqueous solution and the virus.
(PS our study design will rely on 200 proof absolute ethanol for go-to market simplicity and for lowest surface tension deposition into the alveolar pulmonary region to promote alveolar stability)
[1] https://www.cdc.gov/infectioncontrol/guidelines/disinfection...
[2] Ali Y, Dolan MJ, Fendler EJ, Larson EL. Alcohols. In: Block SS, ed. Disinfection, sterilization, and preservation. Philadelphia: Lippincott Williams & Wilkins, 2001:229-54.
In other words, the hypothesis is there is electrostatic attractive forces that rip the buggers apart, in which this “pressure” is quantitatively stronger in the presence of molecular hydrogen bonding, ie greater dipole moments between the aqueous solution and the virus.
(PS our study design will rely on 200 proof absolute ethanol for go-to market simplicity and for lowest surface tension deposition into the alveolar pulmonary region to promote alveolar stability)
[1] https://www.cdc.gov/infectioncontrol/guidelines/disinfection...
[2] Ali Y, Dolan MJ, Fendler EJ, Larson EL. Alcohols. In: Block SS, ed. Disinfection, sterilization, and preservation. Philadelphia: Lippincott Williams & Wilkins, 2001:229-54.
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While we are discussing this, please don’t mind if I ask which is more effective - 70% ethyl alcohol vs 70% isopropyl alcohol?
I am using the hand sanitizer by 3M which has 70% ethyl alcohol.
I am using the hand sanitizer by 3M which has 70% ethyl alcohol.
At first glance, I thought they were comparing two different chemicals.
To minimize confusion, the title could be changed to: Why Is 70% Isopropyl Alcohol (IPA) a Better Disinfectant Than 99% IPA?
To minimize confusion, the title could be changed to: Why Is 70% Isopropyl Alcohol (IPA) a Better Disinfectant Than 99% IPA?
I am not sure if this is the case, but disinfectant that is too aggressive will slowly but surely destroy your skin's top layers.
This is why you shouldn't just be dousing your hands in EtOH/IPA regularly, even if it's 70%. Either use hand sanitizers that have e.g. ethylene glycol to simultaneously moisturize and protect your dermis, or use latex/nitrile gloves when handling dangerous things, sterilize those with alcohol, and wash your hands with hand soap.
> Either use hand sanitizers that have e.g. ethylene glycol to simultaneously moisturize and protect your dermis
Ethylene glycol is a dessicant, and moderately toxic. You really don't want to add that to hand sanitiser, or to rub ethylene glycol on your skin after 70% alcohol as a moisturiser.
You might be thinking about polyethlylene glycol. Or possibly glycerol (a humectant and moisturiser) but that's less likely.
Ethylene glycol is a dessicant, and moderately toxic. You really don't want to add that to hand sanitiser, or to rub ethylene glycol on your skin after 70% alcohol as a moisturiser.
You might be thinking about polyethlylene glycol. Or possibly glycerol (a humectant and moisturiser) but that's less likely.
My bad, I was definitely thinking of Caprylyl Glycol!
I would have thought the fact that splashing IPA over your skin makes it turn white-ish and gives it a weird texture should be a pretty big pointer for people to not do that but I guess people are people.
The top layers of skin are already dead though. You're much more likely to break them down while washing your hands.
They don't destroy the cells themselves, but they wash away oils and significantly dry the skin, quickly leading to skin irritation and potentially cracking.
This is why hand sanitiser usually have some sort of moisturiser as part of the solution, and why if you wash your hand a lot you'll quickly get irritations and worse if yon don't also moisturise them regularly.
This is why hand sanitiser usually have some sort of moisturiser as part of the solution, and why if you wash your hand a lot you'll quickly get irritations and worse if yon don't also moisturise them regularly.
I fear I may have done this to my hands out of ignorance; after frequently assaulting them with alcohol-based sanitizer and dishwashing soap while on lockdown, they now get pruney very quickly when they come in contact with water.
Is this situation irreversible?
Is this situation irreversible?
No, skin is regenerated regularly. You need to destroy it pretty deeply to permanently disrupt this mechanism.
What's been working for me has been keeping a bottle of skin lotion (Lubriderm has been working well) next to the sink. I wash my hands, dry thoroughly, and apply lotion.
I do this at every washing, to assure that my skin is protected after all the oils are stripped by the detergent.
I'm not a dermatologist, however, so consult a medical professional if problems persist.
I do this at every washing, to assure that my skin is protected after all the oils are stripped by the detergent.
I'm not a dermatologist, however, so consult a medical professional if problems persist.
With moisturizers, somewhat. The best hand sanitizers (Avagard, for example) are good at preserving the skin texture. The lipids can be replaced with typical moisturizing lotions. Dish soap is probably not more effective than Dove soap, so use milder soap.
ck2(5)
Many viruses have a hydrophilic outer membrane and the water helps the alcohol to penetrate the virus.