My question is about Determination of Iodine Value in Fats & Oils experiment. I can't seem to get the right IV for coconut oil (Iv = 7-11 range). I followed the procedure used by American Oil Chemists Society, but still I'm getting an IV value of around 1.
The volume of titrant for blank that I got is around 21 mL of 0.1 N Na2S2O3, while with the sample is 18-19 mL.
What could have been the problem? Please help.
Check the normality of Na2s2o3 .
If your blank is larger than the sample by that amount I suspect contamination o the blank.
To determine the iodine value (IV) in fats and oils, the procedure you followed is the right approach. However, there are a few potential reasons why you may not be getting the expected IV value for coconut oil:
1. Inaccurate or impure reagents: Ensure that the reagents, such as the iodine solution, are fresh and correctly prepared. Make sure you follow the recommended concentrations and procedures for preparing the reagents. Impure or outdated reagents can lead to inaccurate results.
2. Incorrect sample measurement: Make sure you are measuring the coconut oil sample accurately. Any error in the volume of the sample used can affect the final IV value. Use a properly calibrated pipette or measuring cylinder for accurate sample volume measurements.
3. Incomplete reaction: The reaction between the iodine solution and unsaturated bonds in the oil is gradual and can sometimes take longer to complete. Ensure that you give the reaction enough time to fully occur, usually around 30 minutes. Insufficient time for the reaction to complete can result in lower IV values.
4. Incomplete solvent extraction: Before performing the titration, it is necessary to dissolve the oil in a nonpolar solvent, such as cyclohexane or petroleum ether. This step helps extract the unsaturated fatty acids from the coconut oil. Ensure that the extraction process is thorough and complete to obtain accurate IV values.
5. Human error: Double-check all the steps in the procedure to ensure there are no mistakes. Small errors, such as incorrect measurements or miscalculations, can significantly affect the results.
If you have checked all the above points and are still obtaining an unexpected IV value, it is worth trying the experiment again to rule out any experimental errors. Additionally, comparing your results with those from other studies or literature can help confirm whether your values are accurate or not.
Note that certain factors, such as the quality or processing of the raw coconut oil, can also affect the IV value. Therefore, obtaining different results than the expected range may not necessarily indicate an error in the experimental procedure, but rather variations in the sample itself.