[Jewelry making - Article 00273] - Re: [Orchid] What is Glacial acetic acid

[Alden & Glenda Blood]

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    Hello Janet, My greeting to you in my last post disappeared as did my
    name at the end.  Gremlins?  I think it has more to do with this Mac
    G4 being new and we still have a lot to learn.  I'll try to get it
    right this time. 

    Glacial acetic acid is pure acetic acid, usually 99.5 percent pure
    (17.5 molar).  It is a clear colorless liquid which freezes on a
    cold day (f.p. = 16.6 deg. C) to give an ice-like solid.  The icy
    appearance gave it the name "glacial".  Acetic acid (also named
    ethanoic acid, CH3COOH) boils at 117.9 deg. C and has a flash point
    of 40 deg. C (closed cup).  The density is 1.0446 grams per cc.  The
    acid has a very sharp nasal membrane ripping odor.  It is quite
    corrosive, especially on skin.  Like most of the concentrated acids,
    it liberates heat on dilution with water, but it is not nearly as
    exothermic as concentrated sulfuric acid. 

    Acetic acid (Ethanoic acid) is prepared in small amounts by
    fermentation processes (vinegars - about 5 percent acetic acid). 
    The large quantity used in industry is prepared by the hydration of
    ethylene over an acid catalyst to yield ethyl alcohol.  The ethyl
    alcohol is oxidized to acetaldehde over a silver catalyst and the
    acetaldehyde is then oxidized to acetic acid.  Another process
    oxidizes ethylene directly to acetaldehyde using a palladium/Cu2O2
    catalyst in hydrochloric acid. The process looks like this (all of
    these steps are carried out in the vapor phase at high temperatures
    and pressures): 

    (1)  H2O + CH2=CH2 over H3PO4 on celetom  yields CH3-CH2OH        

    (2) Then:  CH3-CH2OH  +  O2 over Ag on alumina  yields  CH3-CHO 

    (3) Then:   CH3-CHO + O2 with Mn /Co acetates  yields  CH3-COOH 

    The acid is concentrated and purified by fractional distillation. 
    That is probably more than you wanted to know about glacial acetic
    acid.  But, more information has to be better than the bare minimum
    of information. 

Captain Blood
"Marlinespike Seamanship in Precious Metals"
mariner AT tgtel.com


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