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Conway microdiffusion analysis

  1. Sep 12, 2008 #1

    ~christina~

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    Gold Member

    I really really need information on Conway microdiffusion analysis.
    I know that there is a book but I can't find it and is that the only source of information on this technique? I have looked in my analytical chemistry books and there is NOTHING on it, in there.
    I'm going to do this experiment but I cannot find out the, principles behind the method.
    I read some journal articles but they just refer to the book.

    I know that titration is needed but, why is also a mystery. I do know, from what I've read that the outer ring of the conway dish has a chemical placed into it, and that, that one diffuses into the middle well, which contains fixant chemical (I think that's what it's called), then the fixant is analyzed in the spectrometer. (This may be wrong, so if it is, please correct me)

    If someone knows somewhere online, where I can find info on this, please link me to it. (I can't do the experiment unless I know what is happening and what is this, "conway microdiffusion analysis")


    Thank you.
     
  2. jcsd
  3. Sep 12, 2008 #2

    Borek

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    Staff: Mentor

  4. Sep 12, 2008 #3

    ~christina~

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    Gold Member

    :cry: I found that one already. I figured that was the best one I could find and it didn't explain why the solution was titrated. Thanks anyhow, Borek.
     
  5. Oct 18, 2011 #4
    Hello everyone, I work in a vinegar plant and I used the following procedure to determine ethanol percentage in fermented molassus. I have added some pretext. Hopefully this will help you understand the know-how of this particular procedure -
    ********************************************************

    Determination and Estimation of Ethanol: Conway Method
    Ethanol was determined by Redox titration. In this method ethanol is oxidized to ethanoic acid when ethanol react with excess of potassium dichromate solution (0.05 N) and un-reacted dichromates is then determined by adding potassium iodide (50% KI) solution which is oxidized by the potassium dichromate. Potassium iodide reacts with potassium dichromate and iodine. Then the iodine is treated with a standard solution of sodium thiosulphate (0.1 N). The titration reading is used to calculate the ethanol content after fermentation. One ml Fermented solution was diluted up to in 250 ml, 500 ml and 1000 ml distilled water and took one ml diluted solution as a sample. A Conway unit is used for ethanol determination by this procedure. One ml potassium dichromate was placed into the Conway unit center and sample was placed around the centre. The Conway unit was then covered by a glass plate for 24 hours for reaction. The water and ethanol slowly evaporate, come in contact with Potassium dichromate and then oxidized. More ethanol evaporates until eventually all the ethanol from the fermented dilute solution had left the sample and reacted with the dichromate. One Conway unit was used as a blank and in that unit 1 ml distilled water was used as a sample.
    Alcohol analysis:
    1. Conway unit center (1 ml 0.05 N potassium dichromate solution)

    2. Round (1 ml sample)

    3. Reaction complete within 24 hours

    4. Conway unit centre (50% KI solution 0.5 ml +1-2 drop soluble starch)

    5. Microburate (0.1 N sodium thiosulphate)

    6. Titration

    7. Colorless

    Titration reading:
    Percentage of Ethanol = ((TR of blank sample – TR of FS)× 11.5 × 0.1 × DF × 100)/(0.793 × 1000)
    = Alcohol percentage gm/100ml
    Where, Density of Ethanol 0.793 g/ml
    Volume of sodium thiosulphate used: 11.60 cm3
    DF – Dilution Factor
    FS – Fermented solution
    TR – Titration Reading
     
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