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Author: Subject: Measuring the Total Acid Number (TAN)

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[*] posted on 15-12-2018 at 12:17
Measuring the Total Acid Number (TAN)

Hello World,

What would be the most reliable method for measuring the total acid number in compounds like 2-ethylhexyl nitrate?

I've tried the ASTM D664 method (potentiometric, used for petroleum products - oils and lubricants), the D1613 (colorimetric with phenlophthalein as an indicator; used for volatile compundsused in lacquers and paints) and the D1045 (used for plasticizers; bromothymol blue is used as an indicator). Obviously I've obtained different results with each method. The potentiometric titration gave an indecissive resultus due to the lack of clear eqivalence points and the colorimetric methods use different indicators which change colour in different pH range, thus giving different results. Also by adding KOH (alcoholic solution) into the sample (nitrate ester) the sample changed its colour to yellow so it was hard to tell to when to stop the titration when using phnolphthalein as an indicator. There is also D8045 method which uses thermometric titration but I do not have the access to the equipement yet.

Do you have any ideas how to approach this problem? Also I haven't found any information in the literature on measuring the TAN in nitrate esters. Does the measurement of this parameter even applies to this type of compounds?


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