[TheForge] acid

Mon May 14 08:02:43 EDT 2007

1) Acetic acid is flammable.  It is considered "moderately flammable."  This means it is by no means in the same class as gasoline.  But flammable it is.  What follows is from an MSDS.  

5. Fire Fighting Measures
Flash point: 40C (104F) CC
Autoignition temperature: 427C (801F)
Flammable limits in air % by volume: lel: 4.0; uel: 16.0
Flammable Liquid and Vapor! 
Explosion: 
Above flash point, vapor-air mixtures are explosive within flammable limits noted above. Vapors can
flow along surfaces to distant ignition source and flash back. Contact with strong oxidizers may cause
fire. Reacts with most metals to produce hydrogen gas, which can form an explosive mixture with air. 

2)  Many solvents can pass through the skin to some degree.  We've all heard about DMSO - a fairly polar solvent that not only passes through skin, but carries stuff with it.  There's nothing magic about this.  It's a matter of not being sufficiently repelled by the skin.  Water passes through the skin, as anyone knows who's stayed in a tub or pool too long.  The contrast here is that most acids are either so strong that they destroy the skin on contact or else they cause burning at the surface of the skin.  Some, like HF and concentrated ("glacial") acetic may pass into or through the skin before damage becomes apparent.

Bruce
NJ

>>> sos at alum.mit.edu 5/13/2007 9:11:12 PM >>>
Bruce, admittedly it has been awhile since my various chemistry classes, 
but I really have to question your statements on acetic acid. Two things 
I have a hard time with:
1. "acetic is flammable" I really doubt this. My chemical engineer wife 
can find no mention of it in the rubber bible.
2. "it will pass through your skin" Are you sure you aren't thinking of 
hydrofluoric acid (which does do this)? My hands spent many hours in 
dilute acetic acid in the darkroom in high school with no problems. How 
could people like and consume vinegar?

Steve

Bruce Freeman wrote:
> Dan,
>
> Review "The Chemists Companion" or some other such
> text if you haven't worked with these specific
> chemicals recently enough to fully understand the
> safety hazards.  All those acids and the lye are
> capable of destroying flesh very quickly, so treat
> them with the greatest of respect.
>
> The nitric and the chlorate are perhaps the most
> dangerous because they are oxidizers and can cause
> explosions.  The sulfuric (vitriol) will CHAR flesh or
> anything organic, and actually becomes a stronger acid
> as you dilute it (to perhaps 50%).  Nitric and
> sulfuric and lye can boil the water you dilute them
> with, the reactions are so strong.  Acetic is
> particularly insidious because it will pass through
> the skin like an organic solvent (which it is) and
> cause acid burns to the flesh and bone beneath.  In
> addition, acetic is flammable - you have to store ilt
> like you would any flammable solvent.  All of these
> chemicals will destroy your eyes, should they get into
> them, so wear full-face protection when working with
> them (unless VERY dilute).  You probably already know
> these things, but others reading this may not.  
>
> When diluting acids, add acid to water - slowly - else
> you'll boil hot acid back out at you.  When diluting
> lye, add lye to water slowly with rapid mixing to
> avoid both boiling of the solution and 
>
> All this said, I do not discourage anyone from working
> with these chemicals.  But anyone who does without
> first educating themselves in the dangers is asking
> for terrible trouble.
>
> As to uses:
>
> Ferric chloride solution for etching damascus (or PC
> boards).
>
> Sulfuric (very diluted) for etching steel or copper -
> but different baths for different metals.
>
> Nitric (50% dilution) for passivating SS.  Don't put
> copper in nitric, as it will be etched with the
> evolution of nasty brown NO2 (or N2O4) gas.
>
> Acetic (diluted to perhaps 10%) is great for removing
> scale from steel, but will evaporate if not tightly
> sealed and will stink up your shop like vinegar.
>
> I don't have a use for chlorate, and I suggest caution
> as it could possibly form explosive compounds with
> metals or other compounds.
>
> Bruce
> NJ
>
> --- Daniel Kretchmar <dan at irontreeworks.com> wrote:
>
>   
>> Greetings,
>>           I have just aquired some acid.  I am a
>> science teacher and the 
>> OSHA liason for my Middle School.  Our school just
>> required that any 
>> chemical that has not been used in a classroom
>> within the last three
>> years be disposed of via a Hazardous Waste Disposal
>> Company.  I pretty much 
>> emptied the cabinets, but there were several
>> unopened bottles that just 
>> looked too useful so I took them home.  I have now
>> have:
>> 1 gallon of regent grade Sulfuric Acid
>> 1 liter of Nitric acid
>> 3 liters of distilled Acetic Acid,
>> 1 gallon of crystaline of Potassium Chlorate=20
>> 1 gallon of crystaline NaOH  (lye)
>> 1 pint of crystaline Ferric Chloride
>>
>> Can any suggest a use for these that doesn't go
>> "BOOM"?  I learned alot  of 
>> those in chemistry class. :)
>>
>> I know about safe handling of these chemicals thanks
>> to OHSA training.
>>
>> I have used Nitric Acid for etching in the past and
>> Potassium Chlorate is 
>> great for homemade fire works.  The lye I can use
>> for leather tanning and 
>> the Ferric Chloride for dipping my pattern welding
>> into.......
>>
>> Can anyone recommend a use for the the others or
>> different uses than the 
>> ones I already mentioned?
>>
>>
>> Dan Kretchmar
>> www.irontreeworks.com 
>>
>>
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