What property best represents the neutralization number of transformer oil according to ASTM Method D974?

The neutralization number of transformer oil, according to ASTM Method D974, is expressed as milligrams of potassium hydroxide (KOH) per gram of oil, denoted as mg KOH/g. This measurement indicates the amount of base needed to neutralize the acids present in the oil, which is crucial for assessing its quality and suitability for use in transformers.

Measuring the neutralization number in this way provides a standardized approach to compare the acidity of different oil samples, helping to evaluate their performance and longevity in electrical applications. The use of potassium hydroxide is standard in such analyses because it offers a clear and consistent method for determining how much acidic condition is present in the oil, which can affect the insulation properties and overall health of the transformer.

Other choices do not represent the neutralization number in the context of ASTM D974. For instance, pH value measures the acidity or basicity of a solution but does not quantify the amount of base needed for neutralization. Milligrams of sodium hydroxide per gram (mg NaOH/g) could provide similar information but is not the standard unit for this specific test. Lastly, grams of KOH per liter (g KOH/l) expresses concentration rather than the specific metric used in this