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100% ethanol ?

  1. Apr 3, 2008 #1
    100% ethanol ??

    Hi All

    First off, this is one cool site, lots of neat info.

    Now for my question. I have to clear an argument with one of my students. I work in an emergency department and I was teaching them the role of different alcohol poisonings and how we treat the overdoses. Ever so long ago (15yrs) I was told in bio-chem that 100% ethanol was not possible due to the nature of the molecule. This student works in a lab and said that there was 100% ethanol available.

    SO...... is it possible? or is it really 98%'ish and for the sake of argument labs label it as 100 %

    Thanks all
  2. jcsd
  3. Apr 3, 2008 #2


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    I haven't heard that.

    But ususally, ethanol is denatured, meaning a small amount of another solvent is purposefully added to it.

    A lab I used to work at used un-denatured (= natured?) ethanol, but they had to register with the local Alcohol Control Board. As I understood, that was "pure" ethanol, but I didn't work with it directly so I don't know the details. I do remember that the bottles wouldn't last long, not because we were imbibing, but because it would get contaminated easily by water.
  4. Apr 3, 2008 #3
    100% ethanol is possible, just not from typical distillation. Don't ask me how I know because I will just plead the 5th. :cool:
    Pure ethanol has a great affinity for water and will absorb it from the air until it is only about 96% pure.
  5. Apr 3, 2008 #4
    Thanks all

    Since I only have dial-up at home I could only find out that there is 99.99% pure due to the fact they have to use benzene to remove the 4% water and then remove the benzene. Perhaps a better question is "medical grade ethanol" 100% ? and why would you bother if you could get 96% since I am sure it is very expensive to get that extra 4 % when we mix the ethanol in a saline solution to get 10% solution

  6. Apr 3, 2008 #5


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    Yes, 100% medical grade ethanol is sold as USP grade.

    I use this to recrystallize deliquescent materials. The 190 proof (95%) grade will cause these materials to 'oil out' instead of recrystallizing.
    Last edited: Apr 3, 2008
  7. Apr 3, 2008 #6


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    Yes, for some applications, we need 100% ethanol as well, as water in it will interfere with what we are doing, and yes, it is a LOT more expensive and requires a license to purchase. For most other uses, we use histology grade, which is 95% ethanol and 5% isopropanol and methanol (I don't think how much of each is specified, but if it mattered, I'm sure it could be found out). For medical applications, I don't know of any reason you'd ever need more than 95% ethanol, as long as there was no methanol contamination, and usually 70% is adequate for all the usual purposes.
  8. Apr 11, 2008 #7
    does that considering the hyrogen bonding that can Alcohol form between molecules itself?..if so..certainly alcohol can not ever be in conc. of 100%.
  9. Apr 11, 2008 #8
    in theoretical degree, it is possible.
    by repeating the fractional distillation of a solution of ethanol and water, you will finally get about 96% of ethanol solution in terms of purity. Then, using CaO to help you remove the remained water.

    but in fact, it does not exsit. by both environmental factors and practical factor.
  10. Apr 11, 2008 #9
    It doesn't exist? What do you mean? You cannot certainly make 100% ethanol by distillation, but you can synthesize it in many ways.
    If you use sodium ethoxide, you would need to *add* water, to make ethanol! :

    Na(OCH2CH3) + H2O --> NaOH + CH3CH2OH

    This reaction is also an example of how you can eliminate water from ethanol.
    Last edited: Apr 11, 2008
  11. Apr 11, 2008 #10
    To eliminate water completely from ethanol an example is to use an hydride, as LiALH4:

    LiAlH4 + 4H2O --> LiOH + Al(OH)3 + 4H2
  12. Apr 11, 2008 #11


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