Ứng dụng

The determination of the acid number plays a significant role in the analysis of petroleum products. This is manifested in the numerous standard procedures in use over the world (internal specifications of multinational companies, national and international specifications of ASTM, DIN, IP, ISO, etc.). These procedures differ mainly in the composition of the used solvents and titrants.This bulletin describes the determination of the acid number in petroleum products by applying different types of titration.The potentiometric determination is described according to ASTM D664, the photometric according to ASTM D974 and the thermometric titration according to ASTM D8045.

Fresh as well as used petroleum products may contain acidic components as additives or degradation products. The acid number (AN) is a measure for the relative amount of acids present expressed as mg KOH per g sample. Moreover, AN is used as a quality parameter of lubricating oils both for assessing the quality of new formulations and as an indicator for the degradation of such formulations during service. The use of a pH electrode suitable for non-aqueous titrations ensures the reliable determination of the equivalence point. A flexible sleeve diaphragm facilitates its cleaning especially after use in heavily contaminated samples, such as in used engine oils. Using the correct electrode greatly increases the precision and reliability of the results. This Application Note describes the potentiometric determination of the acid number according to ASTM D664 and IP 177 using the pH electrode Solvotrode easyClean.

Fully automated determination of the total acid number and total base number in engine oils according to ASTM D664 and ASTM D2896 is possible with the OMNIS Titrator.