The method and application of potentiometric acid meter
Use and Importance
New or used oils contain acid or basic components as a result of addition and decomposition products of oxidation. This method can be used to measure the relative changes of the samples. Total acid value is the total amount of these acids under the conditions under which the oil has been measured. The acid value can be used to control the quality of lubricating oil, and sometimes can also be used to measure the consumption of lubricating oil in the process of use. But as the index of lubricating oil scrap is still empirical value.
This method can not be used to predict the corrosion of oil in the process of use because oxidation products will cause the increase of acid value and the change of corrosion of organic acids. There is no relationship between acid value and the degree to which the oil corrodes the metal.
Summary of test methods:
The sample is dissolved in a mixture of toluene and isopropanol containing a small amount of water and titrated with a solution of KOH isopropanol on a potentiometric titrator using a glass indicator electrode and calomel electrode. The potentiometer reading was plotted with the volume of titrant consumed by manual and automatic titration respectively, and the jump point of the curve was taken as the end point of titration. When the curve obtained had no obvious jump point, the end point was the corresponding potentiometer reading of alkaline aqueous solution and acidic buffer solution.