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Topic: Working with Concentrated Acids  (Read 10664 times)

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Offline constant thinker

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Working with Concentrated Acids
« on: May 18, 2006, 08:19:18 PM »
When working with concentrated mineral acids (98% sulfuric acid), will latex gloves be good enough? This is besides the base being near by.

Anyone have any general tips? This is the first time I'll be working with concentrated acids. I've only worked with diluted ones in the past.

I finally managed to find some concentrated sulfuric acid to perform esterifications with. When it eventually comes in I'll be starting off probably with methyl acetate. Then I'll look at my options from there.

Maybe make some other esters then look into transesterification.
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Offline mike

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Re: Working with Concentrated Acids
« Reply #1 on: May 18, 2006, 08:29:24 PM »
You should most probably use thick rubber gloves.

I would usually use butyl or nitrile gloves.

Latex may be ok.

Best idea is don't spill it in the first place.

Also remember that sulfuric acid will react exothermically with water so you also run the risk of heat burns if you are washing it off.

I would also strongly recomend reading the MSDS for sulfuric acid.

Don't forget gloves and lab coat, fumecupboard or good ventilation.
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Offline jdurg

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Re: Working with Concentrated Acids
« Reply #2 on: May 18, 2006, 10:04:43 PM »
Remember that concentrated sulfuric acid gives off a TON of heat when it is diluted.  The heat evolved can cause the water to instantly boil and the glass container it's in to crack.  While it's been mentioned many times, it can't hurt to mention it again.  Make sure that you NEVER add water to concentrated H2SO4.  Always add the concentrated solution to the diluted one.  If you are diluting a great deal of H2SO4, use an ice-bath to house the beaker so that it will not crack from the heat.
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Offline mike

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Re: Working with Concentrated Acids
« Reply #3 on: May 18, 2006, 10:11:33 PM »
Did you know that sulfuric acid is also a carcinogen?

Don't inhale it or spill it on your skin!
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Offline limpet chicken

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Re: Working with Concentrated Acids
« Reply #4 on: May 19, 2006, 01:00:30 AM »
Carcinogenic, yes, but somehow I think the last thing you worry about spilling 98% hot H2SO4 on your skin is cancer, speaking from experience there, the last thing I thought of was "I'm exposing myself to a carcinogen" more like "f&#^$*@ christ on fire get me some NH3" (it was very diluted NH3 solution I had on hand just in case of said spills)
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Offline mike

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Re: Working with Concentrated Acids
« Reply #5 on: May 19, 2006, 01:04:50 AM »
Quote
Carcinogenic, yes, but somehow I think the last thing you worry about spilling 98% hot H2SO4 on your skin is cancer, speaking from experience there, the last thing I thought of was "I'm exposing myself to a carcinogen" more like "f&#^$*@ christ on fire get me some NH3" (it was very diluted NH3 solution I had on hand just in case of said spills)

True, but in most cases people are careful not to spill sulfuric acid, in which case the next worry is exposure limits (and as a carcinogen this has extra implications for those with high exposure). ;)
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Offline jdurg

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Re: Working with Concentrated Acids
« Reply #6 on: May 19, 2006, 08:35:53 AM »
Yes, but stating that H2SO4 is a carcinogen is like stating that Uranium Metal is a chemical hazard.  In both cases you are 100% correct, but in both cases those concerns are really the least of your worries.   ;D
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Offline pantone159

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Re: Working with Concentrated Acids
« Reply #7 on: May 19, 2006, 04:24:46 PM »
Be aware that the stuff likes to attack the caps of containers you might store it in, turning them black.

My personal MO when dealing with the stuff is normally:
1 - Work outside.  (My version of a fume hood).
2 - I keep a decent sized tub of water, with a convenient weak base (e.g. NaHCO3) dissolved in it, to rinse off any spills on my gloves or whatever, and for neutralizing glassware that has acid residue on it.  (I.e., maybe I pour acid from my stock bottle into a beaker, then pour that into some other vessel.  The beaker then goes into said bath.)  Also can be used for diluting any extra leftover acid.
3 - I wear Bluette gloves, which are thick latex (I think) gloves from the hardware store.  (Much thicker than normal 'kitchen dishwashing' gloves.)
4 - I wear, in addition to safety glasses, a 'face shield' on top of that, for extra splash protection.

For esterfication, you don't need to use very much, just a few drops.  For cases like this, it is handy to transfer some of the acid into a much smaller vial, and work from that.  I'll handle vials with a few mL of acid inside, since the amount is small enough that it can't cause TOO much trouble.  I then use a medicine dropper (aka pipette) to transfer the four or so drops of acid to a test tube, then rinse the dropper in a neutralization bath.

One impressive demonstration of the dehydrating power of conc H2SO4 is the following:
(More dangerous than esterfication, but definitely worth trying)
Add around 20 g of concentrated H2SO4 to around 55 mL of sucrose (table sugar).  Stir a bit, and wait.
For a few seconds, nothing much happens, but then lots of stinky and hot fumes start coming off, and then the sugar is turned into a foamy mass of black carbon, which rises up out of the beaker.  What has happened, is the H2SO4 ripped water out of the sugar structure, leaving only carbon behind.

After seeing this, consider that the stuff will try and do the same thing to your hands if you spill it on them.   :)

Offline constant thinker

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Re: Working with Concentrated Acids
« Reply #8 on: May 19, 2006, 04:39:52 PM »
Ok. I'll keep all of that in mind. Thanks guys.
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Offline limpet chicken

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Re: Working with Concentrated Acids
« Reply #9 on: May 19, 2006, 09:32:18 PM »
Mike, at the time, I didn't spill any, it was boiling, and spat droplets onto my hand, ruined a good pair of leather gloves in the process too :(
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Offline mike

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Re: Working with Concentrated Acids
« Reply #10 on: May 19, 2006, 09:35:57 PM »
limpet:*lol* yeah I wasn't trying to have a go at you for spilling it, of course I understand that accidents can happen. Lucky you had the gloves on though, hey mate, better to ruin a good pair of gloves than a good pair of hands. cheers mate, stay safe :)
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Offline limpet chicken

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Re: Working with Concentrated Acids
« Reply #11 on: May 19, 2006, 09:45:00 PM »
Heh, I know you weren't, s#*$ happens, usually when one happens to be working with something particularly unpleasant ;D

Damn acid didn't stop at the gloves either, I have a few scars on my hand from that one, nothing disfiguring though :)
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Offline jdurg

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Re: Working with Concentrated Acids
« Reply #12 on: May 19, 2006, 10:56:36 PM »
Heh.  A good rule of thumb when working with nasty chemicals is that as soon as you take your gloves off, some of it WILL find its way onto your flesh.   ;D  I learned that when I was making sodium iodide for my NaI article here.  I had taken my gloves off assured that I had finished the reaction when one final blob of molten sodium hit a blob of molten iodine.  Immediately a tiny pop happened and molten sodium metal was flung onto the back of my right hand.  Instantly it ate my flesh and left a nasy, open wound.  Hurt like a b$*%( for a few days.
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