METHOD OF DETERMINING BASE NUMBER OF ENGINE OIL Russian patent published in 2013 - IPC G01N33/28 G01N21/78 G01N31/22 

FIELD: chemistry.

SUBSTANCE: method is realised by treating a droplet of an oil sample with a solvent which consists of 50% toluene and 50% isopropanol in the presence of filter paper which is saturated with aqueous solution of bromthymol blue, followed by comparing its colour with the reference colour, wherein the droplet of the oil sample is added to a mixture which consists of 70% of a 20% ethyl alcohol aqueous solution and 30% solvent; 1% bromthymol blue solution is used; after holding in bromthymol blue, the filter paper is soaked with cotton fabric and dried in a horizontal position.

EFFECT: high accuracy of estimation.