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Dr Pepper ASTM Reprocess test

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  • Dr Pepper ASTM Reprocess test

    Ok i did the Dr pepper ASTM reprocess test and the biodiesel that is washed and dried did not gel so added double the amount of methoxide and it formed a weak gel in about 4 minutes.
    I used naoh in the methoxide but the biodiesel was made using koh.
    I also did the other test that i take some of the biodiesel washed and dried and add some more methoxide that contains koh to the biodiesel shake it up and let it sit for 30 minutes and see if any more glycerine settles out or that the methoxide settles on top of the biodiesel.
    In this test no glycerine settled out and the methoxide settled on top of the biodiesel and both were crystal clear.
    So which test is right.
    Why doesnt the dr pepper test make glycerine settle out if the biodiesel does not gel which if it does not gel means its not a complete conversion.

  • #2
    Re: Dr Pepper ASTM Reprocess test

    Hello Dodge,
    In my experience, a re-processed batch of biodiesel may take a number of hours for the glycerine to start settling out.
    If you did not make a gel using the World Famous Dr Pepper ASTM Reprocess test I would suggest you do not have ASTM conversion biodiesel.
    That does not mean it is not very high conversion, just not 98% or better.

    In my experience, if the Dr Pepper Reprocess test does not gel it will drop glycerine by the next morning.

    I suggest you remix the batch with KOH and see what happens to it.

    I suggest you wash the NaOH batch and try the test again. I bet it will gel this time.

    Can you describe the other test you are doing, in particular the quantities of methanol, KOH and biodiesel.

    Tilly

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    • #3
      Re: Dr Pepper ASTM Reprocess test

      250ml of biodiesel washed and dried to that i add 50ml of spare methoxide that was made up for the original conversion using koh.

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      • #4
        Re: Dr Pepper ASTM Reprocess test

        Hello Dodge,
        That is just like doing a fresh process. it will certainly have a lot of methanol and KOH in it. With that much methanol it may dilute any glycerine produced so much that it might all float on the top anyway.
        If you had used NaOH instead of KOH it would certainly have gelled immediately because of the excessive NaOH making lots of soap whether you had a complete reaction or not. I did that enough in my early days.
        .
        However, while your KOH will also make lots of soap, it will not readily gel.
        The "Standard" reprocess normally used is 50ml methanol and 1g NaOH/1.4g KOH adjusted for purity mixed into 1 litre Biodiesel to be reprocessed.
        If you did the re-process using 1.4g KOH mixed into 50ml methanol it should give you either glycerine on the bottom or nothing.
        It may take a number of hours for the glycerine to settle out.

        That is why theWorld Famous Dr Pepper ASTM Reprocess is so handy, it gives you an answer in 5 minutes instead of having to wait over night to be sure nothing is really going to drop out.

        Tilly
        tillyfromparadise
        Senior Member
        Last edited by tillyfromparadise; 30 April 2006, 11:00 AM.

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        • #5
          Re: Dr Pepper ASTM Reprocess test

          Ok thanks will do it properly next time and if no gel will will leave overnight.

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