y 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.
Accdg to Dr. Bob, it's possible the blank is contaminated. What's the usual volume for blank? Thank you.
To determine the Iodine Value (IV) in fats and oils, it is important to ensure accurate and precise results. One factor that can affect the accuracy of your results is the contamination of the blank solution.
The blank solution is used to account for any impurities or background color that may interfere with the titration. It should contain all the reagents used in the analysis, except for the sample itself. In this case, the blank involves measuring the volume of 0.1 N Na2S2O3 solution required to neutralize the excess iodine after the reaction with the sample.
The typical volume of blank solution may vary depending on the specific procedure or laboratory practice. However, it is generally recommended to use a volume similar to that of the sample solution. This ensures that any impurities or background color present in the blank solution are properly accounted for in the titration.
In your case, you mentioned that the volume of titrant for the blank solution is around 21 mL of 0.1 N Na2S2O3, while for the sample it is 18-19 mL. There seems to be a significant difference between the volumes of blank and sample titrations. This discrepancy suggests the possibility of contamination in your blank solution.
To address this issue, follow these steps:
1. Prepare a fresh blank solution using the same reagents and concentrations.
2. Make sure all glassware and equipment are clean and free from any residues.
3. Store reagents properly, avoiding exposure to light and air.
4. Minimize any sources of contamination during the analysis, such as dust particles or oily residues from previous experiments.
5. Concentrate on proper technique during the titration, ensuring accurate measurement of volumes.
6. Check the expiry dates of your reagents and verify their concentrations if possible.
By taking these precautions and paying attention to the quality of your blank solution, you can reduce the chances of contamination and obtain more accurate IV values for your coconut oil sample.