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Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: beanfiend98 on November 12, 2021, 09:00:33 AM

Title: Iodine Value, Varying Sample Weights
Post by: beanfiend98 on November 12, 2021, 09:00:33 AM

I've recently started performing an iodine value titration for fatty acids, specifically following AOCS's Wijs Method (Tg 1a-64).  According to this method, it recommends adding varying oil sample amounts depending on expected iodine value.  For example: adding 0.1954-0.2442g when IV=130 or adding 0.3175-0.3969 when IV=80.  I've attached a picture of the table.

I've looked at other methods online and this doesn't seem to be consistent across methods: some say to add 10g or 100g no matter the sample. 

I'm wondering if anyone can explain why this might be? I haven't been able to find explanations in my method or the others.  I would have thought that in most cases, especially where you're unsure of the IV, a consistent sample weight would be the way to go.

Title: Re: Iodine Value, Varying Sample Weights
Post by: Borek on November 12, 2021, 02:02:07 PM

Most likely they suggest different amounts of acids to force optimal use of titre volume (about 80-90% of the burette volume).