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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 10 Issue 5 (2005) pp 363-366

Potentiometric Analysis of Total Base Number in a Lubricant: An Analytical Chemistry Experiment

M. Nasiruddin Khan,†* Sadaf Bhutto, Anila Sarwar,§ and Muti ur Rehman

Department of Chemistry, University of Karachi, Karachi-75270, Pakistan, nasirk@myway.com; Government Degree Science and Commerce College, F.B.Area Karachi, Pakistan; and §Fuel Research Centre, PCSIR, Karachi, Pakistan.
Received April 5, 2005. Accepted July 10, 2005.

Published online: 20 September 2005

Abstract. Potentiometric acid–base titration is a routine exercise in the general and introductory chemistry laboratory course. Using experiments that involve familiar consumer products can make these laboratories more relevant to students. In the experiment described here, the total base numbers (TBN) of lubricant oil samples, common consumer products are determined. The TBN generally indicates the acid-neutralizing capacity of a lubricant, which decreases with use and is highest when the oil is new. The experimental procedure requires the extraction of hydroxide ion into an aqueous phase followed by potentiometric titration. The experiment also illustrates the usefulness of a Gran’s plot as compared to a derivative plot for the determination of the equivalence point. The results obtained are comparable with those obtained using the standard ASTM method. A comparative study was conducted for lubricant samples used in various engines that consume different types of fuels. This experiment can be used at the B.Sc. Honors level or in introductory analytical laboratory courses.

Key Words: Laboratories and Demonstrations; general chemistry; lubricant; total base number; potentiometric titration; extraction; laboratory experimentspectroscopy

(*) Corresponding author. (E-mail: nasirk@myway.com)

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Issue date: October 1, 2005

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