What are the units of TBN??

[wcbcruzer]

Hi, when you get a TBN analysis, what unit is it reported in? Is it pH? Molality?

 

[crinkles]

mg KOH/g

 

[wcbcruzer]

Ok cool... So motor oil has KOH in it?? Or is it equivalents of OH that you need to convert to mg KOH?

 

[crinkles]

probably equivalents of basic parts converted to KOH, like calcium sulphonate? i'm outta my depth here

 

[wcbcruzer]

Thanks. I'm going to try to figure out the TBN of an oil sample. We'll see if it works.

 

[Dominic]

sounds like a titration is needed to calc TBN?

 

[wcbcruzer]

Yea, I plan on titrating it with a strong acid, then doing calculations to get the final units of mg KOH/g sample.

 

[Colt45ws]

Find the Actual ASTM test methods. Should have white paper. That will be cool if you can DIY your TBN.

 

[Gary Allan]

Give me the pony style on this. I've titrated aqueous solutions with boiler chemistry ..but just how does one get indications of neutralization in motor oil?

We would hit the sample phenolphthalein which would either be invisible or turn it red depending on the polarity. You would then add acid until it either disappeared or appeared (another reagent was added).

So help the lab challenged.

 

[Vilan]

Yep. You'd need some kind of pH indicator in there so you can see when it becomes neutral. Phenolphthalein is good for water, not sure what kinds are oil-soluble, or how easy it'd be to see the color change in a motor oil.

 

[Tom NJ]

TBN is a measure of the acid needed to neutralize some or all the bases present in the oil sample. It is expressed in mgKOH equivalents per gram of sample.

The phenolphthalein method is a colormetric titration and does not give a true TBN.

TBN is determined using a slow potentiometric titration with an acid and the pH is plotted. The end point is an inflection in the pH plot or, if no inflection occurs, a standardized pH. The oil sample is dissolved in an organic solvent.

Different TBN methods use different acids and solvents, and give different results depending on the ratio of strong and weak bases present.

You can find more information here:

http://www.oilanalysis.com/article_detail.asp?articleid=1139

Tom NJ

 

[SteveSRT8]

wow.

thank you for the concise illumination.

I am enriched!

 

[wcbcruzer]

Thanks Tom NJ for the link. Some good info in there. The conductance method to determine TBN is a clever idea!