My SRM for ASTM D4739 is NIST 1848 Lubricating oil additive. It's certified value for TBN is 44~55.2. But my results show negative values.
Other samples results are minus as well.
I use Mettler Toledo Autotitrator.
Why do I get negative values on TBN?
Is there any other SRM available for ASTM D4739 not D2896? Please recommend one.
Thanks,
Viv
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