TBN analysis methods

Dexsil is listed in Noria's product directory. Here's a link to their Titra Lube TBN test kit.

http://www.dexsil.com/products/detail.php?product_id=38

I have tried my own methods, using back titration method. I use kerosene (as lubricant solvent), alcoholic HCl (ethanol-HCl), water (as polar solvent) and NaOH to measure the TBN.I use phenolphthalein indicator. But, my TBN was not the same with the theoretical value (the different is almost 1/2 times the real value). I don't know the probems. But i still can't detect the decrease of TBN value. Any comments to my methods ?

We use 100 ml. of the TBN solvent (Chlorobenzene and Acetic Acid mixture (2:1) ratio) and titrate 0.1 gm to 0.3 gm weight of used oil sample with 0.1N perchloric acid using p-naptholbenzein as the indicator.

There is ASTM method for colour indicator titration Try it

As far as my experience is concerned, it is better to follow some universally accepted methods like ASTM D 2896 for fresh oils and ASTM D 4739 for used oils, than developing our own methods. Colour indicator titration method – ASTM D 974 – is also good to try out, as mentioned in the above post. Because majority of the oil companies are following these methods. ASTM is conducting some lab crosscheck programs also to bring the uniformity in the test results.

Since these methods – ASTM D 2896 and ASTM D 4739 - are based on some potentiometric titration principles, no external colour indicators are needed to identify the EP’s.

Thanks for your info