Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    • Thread Starter

    Wondering if anyone could explain this?

    For my Advanced Higher chemistry project i decided to make biodiesel.

    The procedure is basically as follows;

    1) 100ml sunflower oil in a 250ml flask with 15ml methanol added to it.
    2) Slowly add 1ml (50% sol.) potassium hydroxide using a 1 ml pipette.
    3) Stir mixture thoroughly for 10 minutes.
    4) Allow mixture to sepparate into 2 layers (one which is pure biodiesel and the other impure biodiesel).
    5) Remove the top layer of impure biodiesel and wash the pure biodiesel with 10ml deionised water.

    The thing is, when i try to light the pure biodiesel it won't burn but the impure biodiesel burns quite well with a yellow flame and with grey smoke (obviously due to being impure).

    My theory is that in a diesel engine a great deal of pressure is required to burn diesel and this pressure is fundamental to my batch of biodiesl burning.

    Can anyone back-up or discredit my theory and explain why the impure biodiesel burned so well?


    1. Go to this site and learn how different engines work.

    Your theory about how a diesel engine works should then become the facts about how they work. :-)

    2. Diesel, (and biodiesel) have a high flashpoint, and will not ignite with a match at room temperature. I would exercise considerable caution in igniting anything like this. Wear goggles, labcoat, work in a fume hood, and have a CO2 fire extinguisher nearby. I can't explain exactly why your impure stuff is burning. Perhaps it's some of the methanol?


    3. You've "washed with water". Have you separated off the water fraction? I suspect that your pure stuff will be somewhat wet. I think this is probably why it won't burn.
    • Thread Starter

    Thanks very much for the input, I'm not going to be back in school until Thursday but I will post my results once I get to the bottom of this.

    I reckon your right about the flash point which is a shame because I really qould like to see this burn and be able to compare it to other fuels, ah well.
Submit reply
Turn on thread page Beta
Updated: February 14, 2010
Do you agree with the proposed ban on plastic straws and cotton buds?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.