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View Full Version : Does dipping something metal in rubbing alcohol sterilize it?


biddee
05-09-2004, 10:03 PM
When we were kids and used to run around barefoot, we often used to get thorns in our feet. My mom used to use a needle to dig them out, and would dip the needle in rubbing alcohol to sterilize it before beginning. Does this really work?

Qadgop the Mercotan
05-09-2004, 10:09 PM
IIRC, it does a pretty fair job of killing most of the germs, but only if the alcohol is allowed to dry on the item being cleaned. You can't just wipe it off right away.

QtM, MD

easy e
05-09-2004, 10:45 PM
It's not rubbing alcohol, but in 3 labs I've worked in, we used a 70% solution of ethanol (drinking alcohol) to wipe down the insides of laminar flow hoods, our instruments, and our hands to create a "sterile" environment inside.

scr4
05-09-2004, 11:55 PM
It's not rubbing alcohol, but in 3 labs I've worked in, we used a 70% solution of ethanol (drinking alcohol)...
Sorry for a minor hijack, but isn't that what rubbing alcohol is?

Blake
05-10-2004, 12:04 AM
Rubbing alcohol is isopropanol, not ethanol.

CrazyCatLady
05-10-2004, 01:23 AM
Kinda depends on how you define "sterile". Alcohol will kill just about anything if it's on there long enough, but it evaporates pretty damned fast, often too fast to kill the tougher stuff. It will usually greatly reduce the amount of bacteria and such on something, though. Still, I wouldn't really call that "sterile" so much as "less contaminated".

ccwaterback
05-10-2004, 01:38 AM
The needle we used to get was first heated over a gas flame on the stove, I'm not sure if that's any better.

I remember our barber used to have a big jar of alcohol he used to store his working combs. Now they seem to use UV light devices.

Eleusis
05-10-2004, 01:46 AM
Since I started brewing beer and wine, I've learned a few things about cleaning, sanitization, and sterilization.

If your metal object has not been cleaned before you dunk it in alcohol, microbes can survive within any "goo" that might exist in the cracks and crevices.

Say, for example, you have a quart mason jar, which you fill halfway with sugar water, and allow to sit in the open air to be colonized by various bacteria and wild yeasts, until all the the water evaporates. You'll be left with thick sticky gunk in the bottom of the jar. In this case, merely dunking it in alcohol, or even soaking it (depending on various factors), will probably not effectively sterilize the jar.

It's an extreme example, but you see my point.

If the metal object really needs to be sterile, make sure it's cleaned of any gunk or deposits, and soak it for minutes rather than seconds.

In practice, there probably isn't much food for bacteria on a sewing needle in the first place, and a quick dip in alcohol will probably sufficiently sanitize it.

David Simmons
05-10-2004, 02:35 AM
Rubbing alcohol is isopropanol, not ethanol.

Or in the bad old days, methanol.

kniz
05-10-2004, 02:36 AM
Many years back the regular procedure was to sterilize all medical paraphernalia in rubbing alcohol. Needles were used over and over and were kept in a container of alcohol. Today we throw away needles, which not only means the one being used is lots more sterile, but also is sharp and doesn't hurt like dull needles that had been used many times. I believe drinking alcohol was mostly used as an antiseptic in cowboy movies.

Kegg
05-10-2004, 02:44 AM
Alchol must be 70% to sterilize. weaker won't do and stroger will cause the outer covering to harden. (I think)
_______________________________________________
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KP
05-10-2004, 03:31 AM
A flame is actually an excellent way to sterilize metal. Bacteria are just tiny bags of protoplasm that dry up or burn quickly on red-hot metal. Even their spores, which can be tough little buggers, will burn or be so messed up sthat they don't pose much risk (due to protein denaturation, etc.) Even if a few live bacteria survive a cursory flaming, they won't hurt you, if they're in no shape to multiply.

UV mostly works by messing up DNA (e.g. creating thymidine dimers, and base conversions.) It's slower than alcohol, but more effective against viruses if the UV exposure is long enough. Dilute bleach solutions are also used to chemically 'sterilize' viruses, which have no physiology and aren't really alive to begin with.

Alcohol is a perfectly decent sterilizing agent, but even a good soap cleaning will make the needle far cleaner than the thorn you're digging out. [BTW, Eleusis is right about using a clean needle, even if you're going to sterilize it.] The additional sterilizing effect of alcohol is mostly useful when needles are often re-used [home first aid or medical settings]. "You don't know where it's been" applies more than ever to needles that may recently have been inside a pus-filled absess.

Now aren't you glad we mostly use disposables now?

Interestingly, though ethanol (and isopropanol) works mostly by dehydrating the bacteria, 100% or 95% ethanol don't sterilize nearly as quickly or well as 70% ethanol. A few seconds exposure is adequate: As little as 30 secs will give results essentially as good as days of immersion. As you can imagine, sterilizing with ethanol been well studied, and 70% ethanol is widely sold, precisely because it was found to be nearly optimal. So if you MUST sterilize with vodka or grain alcohol, as in some old movies, aim for 140 proof, even if you have to dilute it a bit.

100% ethanol is uncommon outside of chemistry labs, because ethanol will avidly suck water out of the air, if necessary, to create a 95% water/ethanol azeotrope. You can't even distill it to better than a 95% solution; it'll bring 5% water with it. That's why 95% [190 proof] is the practical limit for grain alcohol or liquors. To make ethanol stronger than this, you have to run it through a bed of anhydrous dissicants [special water-sucking chemicals], -- if you think shaking bruises gin, try running it through anhydrous copper sulfate.

chorpler
05-10-2004, 04:00 AM
Wow, this is interesting. Our local grocery store sells 70% isopropyl alcohol, of course, like everybody else ... but they also sell 99% isopropyl alcohol, which I've never seen at any other grocery store. If 70% sterilizes better, why do they sell 99% as well? Are they just preying on ignorance?

I use the 99% alcohol to clean out computers that stuff gets spilled on, figuring that 99% alcohol will evaporate faster and leave less residue than 70% will. Now I wonder if that's true.

Snooooopy
05-10-2004, 05:59 AM
Interestingly, though ethanol (and isopropanol) works mostly by dehydrating the bacteria, 100% or 95% ethanol don't sterilize nearly as quickly or well as 70% ethanol. A few seconds exposure is adequate: As little as 30 secs will give results essentially as good as days of immersion. As you can imagine, sterilizing with ethanol been well studied, and 70% ethanol is widely sold, precisely because it was found to be nearly optimal. So if you MUST sterilize with vodka or grain alcohol, as in some old movies, aim for 140 proof, even if you have to dilute it a bit.

100% ethanol is uncommon outside of chemistry labs, because ethanol will avidly suck water out of the air, if necessary, to create a 95% water/ethanol azeotrope. You can't even distill it to better than a 95% solution; it'll bring 5% water with it. That's why 95% [190 proof] is the practical limit for grain alcohol or liquors. To make ethanol stronger than this, you have to run it through a bed of anhydrous dissicants [special water-sucking chemicals], -- if you think shaking bruises gin, try running it through anhydrous copper sulfate.

I know a girl who can suck like anhydrous copper sulfate. She knows how to create a hard, throbbing azeotrope, sure enough.

ftg
05-10-2004, 12:22 PM
Wow, this is interesting. Our local grocery store sells 70% isopropyl alcohol, of course, like everybody else ... but they also sell 99% isopropyl alcohol, which I've never seen at any other grocery store. If 70% sterilizes better, why do they sell 99% as well? Are they just preying on ignorance?

I use the 99% alcohol to clean out computers that stuff gets spilled on, figuring that 99% alcohol will evaporate faster and leave less residue than 70% will. Now I wonder if that's true.

For cleaning electronics, the less water the better. I can only get 90% Isop. at drug stores. For the 99% stuff I have to go to electronics supply houses. In particular, 99% stuff is best for cleaning video heads. (So a little of that goes a long ways.)

robby
05-10-2004, 10:58 PM
Rubbing alcohol is isopropanol, not ethanol.
FWIW, I have a bottle of Lavacol (http://westburypharmacy.com/westburystore/prods/074625.html) brand rubbing alcohol, whose ingredients are listed as "70% denatured ethyl alcohol" [ethanol].

I've always had the understanding that "rubbing alcohol" = "isopropanol", so I was surprised to see this on the label.

Smeghead
05-10-2004, 11:52 PM
One common way of using ethanol to sterilize things in the lab is flaming - you dip your object in the ethanol, take it out, then light the residual alcohol on fire.

galt
05-11-2004, 12:53 AM
if you think shaking bruises gin, try running it through anhydrous copper sulfate.Interesting. I've always been a little skeptical of the concept of "bruising" gin, but I've never heard this explanation before. Can you elaborate on this? If I read you correctly, the gin is bruised by "sucking up" too much water, which the shaking somehow facilitates. Is that right? Can you bruise gin that doesn't have ice in it (sucking water from the air bubbles that get mixed in), or is the ice necessary?

I'm really curious whether bruising is something that really affects the taste in a noticeable way, or if it just gives people something to be snobby about.

danceswithcats
05-11-2004, 01:18 AM
FWIW, I have a bottle of Lavacol (http://westburypharmacy.com/westburystore/prods/074625.html) brand rubbing alcohol, whose ingredients are listed as "70% denatured ethyl alcohol" [ethanol].

I've always had the understanding that "rubbing alcohol" = "isopropanol", so I was surprised to see this on the label.

The key to your query lies in the word 'denatured' meaning, rendered unfit for drinking without impairing other useful properties.

Ethyl alcohol, aka ethanol or grain alcohol = CH3CH2NH2

Isopropyl alcohol, aka rubbing alcohol = (CH3)2CHOH

Methyl alcohol, aka methanol or wood alcohol = CH3OH

Q.E.D.
05-11-2004, 01:37 AM
Ethyl alcohol, aka ethanol or grain alcohol = CH3CH2NH2
Try again.

danceswithcats
05-11-2004, 01:50 AM
Try again.

My bad. That should have been CH3CH2OH. :smack:

KP
05-11-2004, 02:46 AM
Hey Galt, Love your Gulch. How's Francesco?

I was just cracking wise. All I meant was that running any good liquor through CuSO4 is likely to wreck it, for reasons unrelated to the removal of water.

To be honest, I've always been skeptical of "bruising gin" myself (my drink of choice the year I was 23, until a GF innocently noted that it tasted like Pine Sol (tm) --a brief period, true, but if memory serves I knocked back an awful lot of it that year). However, in a few double-blind clinical trials over the years, some of my friends have been able to tell if their gin had been deliberately bruised. I think I've tasted a difference myself, on the few times I've had gin since the 1980s, but those weren't double blind, and I don't consider them a fair test.

My personal curiosity ended once I convinced myself that I preferred martinis stirred not shaken (As silly as it might sound to model a preference after some over-hyped self-parody of a fictional character, I had an odd aversion to that conclusion) Might I suggest that you conduct your own double-blind trial. After all, only two matter when it comes to mixing drinks:

1) knowing -really knowing- what you personally prefer
2) making a guest their drinks as they request them. It's hospitality, not science.

C'mon, do you want to be one of those obnoxious people who keep slipping Miracle Whip(tm) into sandwiches on the theory that, since you don't care which you get, anyone who says they do are faking it? Even if they usually, or always, taste it and complain?

(Someday I'm going to write a paper on that practice. I know a disturbing number of wives -is it always the wives?- who did that to their hubbies for years. All were divorced but one. If you ask me, that's every bit as vital a topic as any experiment I could add to the literature on antiseptic alcohols.)

David Simmons
05-11-2004, 02:54 AM
My personal curiosity ended once I convinced myself that I preferred martinis stirred not shaken (As silly as it might sound to model a preference after some over-hyped self-parody of a fictional character, I had an odd aversion to that conclusion) Might I suggest that you conduct your own double-blind trial. After all, only two matter when it comes to mixing drinks:


[joke?]

A traveler who was going to the darkest Amazonian jungle described his list of equipment to a friend. It was complete and had been checked by the most experienced jungle experts.

"You forgot the gin and vermouth," said the friend.

"What do I need that for?"

"Well, when you are lost and all alone and about to perish take out the gin and vermouth and start mixing. Someone is sure to pop out of the bush and say, 'That's not how you make a Martini!' and you are saved."[/joke?]

Snooooopy
05-11-2004, 05:50 AM
Try again.

For the curious, CH3CH2NH2 appears to be ethylamine. Try not to drink it ... or, as we see from the following, shove it in your bunny's eyes.

* Summary of toxicology

1. Effects on Animals: Ethylamine is an eye, skin, and upper respiratory tract irritant; it also causes kidney, liver, and myocardial damage. The 4-hour LC(50) in rats is 3,000 ppm, and the dermal LD(50) in rabbits is 390 mg/kg [NIOSH 1991]. Rabbits exposed to 100 ppm ethylamine for 7 hours/day, 5 days/week for 6 weeks developed corneal and lung irritation and liver and kidney damage. Rabbits exposed to 50 ppm in the same regimen developed corneal injury after 2 weeks of exposure and showed lung irritation and myocardial degeneration at autopsy [ACGIH 1991]. One drop of a 70-percent solution of ethylamine instilled in the eye of rabbits caused damage rated 9 on scale of 10, with 10 denoting the severest injury [Grant 1986]. Intermittent exposure to 50 ppm ethylamine for 10 days caused severe eye irritation in rabbits [NIOSH 1991]. Direct contact of the skin of guinea pigs with a 70-percent aqueous solution caused necrosis and deep scarring [Hathaway et al. 1991].

2. Effects on Humans: Exposure to ethylamine causes eye, skin, and upper respiratory tract irritation in humans. Workers have reported experiencing temporary blue, hazy vision after exposure to ethylamine; this effect is believed to be related to corneal edema [Grant 1986]. Eye irritation and corneal edema have been reported from occupational exposure [NLM 1992]. Direct contact of the eyes or skin with the liquid may cause permanent eye damage and skin burns. Systemic poisoning is manifested as headache, nausea, faintness, and anxiety [Clayton and Clayton 1982]. Inhalation causes respiratory irritation, coughing, and difficulty breathing [Genium 1993].

BJMoose
05-11-2004, 11:46 AM
. . . a GF innocently noted that it tasted like Pine Sol. . .
So. . .did it ever occur to you to ask her how she knew what Pine Sol tastes like?

Biffy the Elephant Shrew
05-11-2004, 12:16 PM
Interesting. I've always been a little skeptical of the concept of "bruising" gin, but I've never heard this explanation before. Can you elaborate on this? If I read you correctly, the gin is bruised by "sucking up" too much water, which the shaking somehow facilitates. Is that right? Can you bruise gin that doesn't have ice in it (sucking water from the air bubbles that get mixed in), or is the ice necessary?

I'm really curious whether bruising is something that really affects the taste in a noticeable way, or if it just gives people something to be snobby about.
I thought that gin was "bruised" by being aerated when shaken. It's diluted by being shaken with ice.

robby
05-19-2004, 10:51 AM
The key to your query lies in the word 'denatured' meaning, rendered unfit for drinking without impairing other useful properties.
My comment (not query) had nothing to do with the adjective "denatured." Instead, I was simply noting that this manufacturer was labeling denatured ethanol as "rubbing alcohol," as opposed to isopropanol.

Incidentally, according to this MSDS (http://syndel.com/msds/denatured_ethanol_msds.html), ethanol is denatured primarily by mixing it with methanol (along with small amounts of ethyl acetate and methyl ethyl ketone).

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