AN

   
OELCHECK test instrument: Metrohm 855 Robotic Titrosampler
Sample quantity: 30 ml 
Unit: mgKOH/g
Test result: AN (Acid Number), SAN (Strong Acid Number)
Result range: 0.1 - 260 mg KOH/g
Analysis for: Engine and gear oils
Brief description: The AN indicates the amount of potassium hydroxide required to neutralise the acids contained in a gram of oil. If the sample is too dark to determine the neutralisation number at which an indicator, when added to a mixture of oil and solvent, will indicate the neutral state through a colour change, the AN shall be determined for these samples. In that instance, a titrant (KOH) is added to the mixture of oil and solvent until it is "neutral". This is detected using a potentiometer and is shown by an inflection point in the titration curve. With the consumption of titrant up to this inflection point or up to the specified pH value, the acid number can be calculated in mg KOH/g.
Underlying test standard: ASTM D664