BIODIESEL TITRATION LAB

This assay measures the level of free fatty acids present in oil and therefore determines the amount of additional sodium hydroxide that needs to be added during the reaction to neutralize the oil.

NOTE: Students may be asked to complete more than one trial, then average the results.

Materials

• 
  Samples of fresh and used canola oil (If used frying oil is not available, create used oil by heating it until it turns brown. Consider obtaining some from the cafeteria, if canola oil is used for cooking.)


• 
  99% isopropanol solution (IPA)
  


• • Titrant – 0.1% solution of sodium hydroxide ( 1 g NaOH added to 1 L of water or 0.025 moles/litre of titrant)


• 
  • pH indicator (phenolphthalein, turmeric or other indicator able to indicate pH 7.0)


• 
  • Clean sample cup (100 mL Erlenmeyer flask or plastic sample cup)


• 
  • Disposable plastic pipettes or graduated cylinders capable of an exact measurement of 1 mL of oil


• 
  • Burette

Test Method

1. Measure 10 mL of 99% isopropanol solution into an Erlenmeyer flask.
2. Add a small amount of pH indicator to the solution (3 drops of phenolphthalein or a dusting of
turmeric powder).
3. Use a disposable plastic pipette or graduated cylinder to measure exactly 1 mL of oil and pour it into the flask.
4. Stopper the flask and mix the solution of alcohol and oil by shaking it gently.
5. Fill a burette with the titrant (0.1% NaOH).
6. Slowly add the titrant to the Erlenmeyer flask and mix during addition.
7. Stop adding the titrant once pH =7 is determined by the colour change. For example if using
tumeric, the colour changes from yellow to pink. If the solution remains pink for at least 10
seconds the pH is 7; if the colour turns bright red, too much titrant was added and it is necessary to start over.
8. Record the amount in mL of titrant added to create a colour change.
9. This value (acid number) indicates the amount of additional NaOH required to neutralize the free fatty acids in g/L.
10. Calculate the amount of NaOH required to conduct the reaction using the following equation –
NaOH required (g/L of oil) = 3.5 + acid number.
Example if 2 mL of solution is required, acid number = 2