ctice $-$ Experimental assignment Biodiesel

Appendix: M separatory funnel

Note: Clean and dry glassware is essential for the success of this experiment, therefore, wash all the required glassware and rinse with methanol before use.

Set up reflux apparatus $($see Appendix D$)$ Place a heating mantle $($turned off$)$ on top of a magnetic stirrer and under the reflux apparatus. Connect the heating mantle to a rheostat. Use lab jacks to allow quick removal of heat.

Weigh about $50g$ of vegetable oil in a graduated cylinder and record the volume. Pour the oil into a $100mL$ round bottom flask.

Measure $20ml$ methanol into a $125mL$ Erlenmeyer flask.

Calculate the amount of KOH required $($potassium hydroxide base catalyst needed is $1\%$ by weight of the oil used$),$ again this might be different than the number you got in the prelab calculation since that assumed exactly il was measured.

Safety concern: Potassium hydroxide $($a strong base$)$ can cause severe burns to skin.

$5.$ Quickly mix the KOH into the methanol in the Erlenmeyer flask. Swirl the solution until all the KOH is dissolved, heat gently if necessary. Cover the solution with a watch glass.

$6.$ Place a small dry magnetic stirring bar into the flask. Slowly add the methanolic solution to the oil and assemble the reflux apparatus. Carefully heat the mixture gently under reflux for one hour using a heating mantle to heat and the magnetic stirrer to stir the solution.

$7.$ Cool the mixture, recover the magnetic stir bar, transfer the mixture to a separatory funnel. Remove the aqueous layer $($glycerol and unreacted oil$).$

Thought question: which one is your aqueous layer?

To the organic layer $($biodiesel methyl esters$),$ add $15$ drops of concentrated acetic acid and swirl the mixture.

SAFETY CONCERN: Any acid can cause burns if it gets on your skin so always handle it with care. If you spill some, wash the area immediately.

If the acid gets on the container, close the lid and then put it in the sink and wash the outside of the container. This is to make sure no one else could inadvertently burn themselves. Concentrated acetic acid is corrosive, causes burns and is a lachrymator.

Thought question: what is the purpose of adding Acetic acid?

$9.$ Wash the organic layer with $20mL$ of hot tap water $($in two steps using $10mL$ each time$)$ discarding the aqueous layer. It is very easy to get emulsions in this step, which will not separate easily. To avoid this try not to shake the content of the flask too hard.

$10.$ Collect the organic layer and measure the final volume and weight of the product.