ASTM D5768 Determination of Iodine Value of Tall Oil Fatty Acids
Tall oil fatty acids are isolated from the bi-products of paper production. They are used in drilling fluids, metal working fluids and lubricants because of their attractive biodegradability, cost and physical properties. The main drawback of these tall oils is the presence of double bonds which may lead to oxidation and shorten the life of the fluid or lubricant. This test may be used to estimate the level of unsaturation (number of double bonds) in tall oil fatty acids by determining the iodine value. A low iodine value indicates a low level of unsaturation, and possible slower rate of oxidation.
A weighted sample is placed into a flask and dissolved in solvent. An acidic solution of chlorine and iodine is added and the solution is given time to react. Potassium iodide is added and the solution is titrated with sodium thio-sulfate to a visible endpoint using a starch indicator. The blank is subtracted and the iodine value is reported.