Question

A fat with a high acid number is said to be____

Answer 1

Hint: The acid number is used to quantify the acidity of a substance. It is expressed in milligrams of potassium hydroxide that is required to neutralize the acidic constituents in \[1g\] of a given sample. It is a common parameter in the specification of fats and oils.

Complete step-by-step answer:
The acid number is defined as the amount of potassium hydroxide (\[KOH\], in milligrams) necessary to neutralize the free fatty acids contained in \[1g\] of a chemical substance. The high acid number indicates the deterioration of oil fats. On the other hand, a low acid number indicates good cleansing by soap. The acid number indicates the FFA (Free Fatty Acid) content of transesterified biodiesel. Free fatty acids are those acids that are not present as fats in biodiesel.

Acid values are inversely proportional to saponification values because when a number of fatty acids are present in the biodiesel as fats, the greater the saponification value; therefore, the number of free fatty acids present is low, thus giving a lower acid value. Hence, fat with a high acid number is said to be Free of Fatty Acids (FFA).

The weight of free fatty acids (FFA) present in the biodiesel divided by the entire weight of biodiesel gives the FFA percentage.
\[AV = 1.99{\text{ }}FFA\% \]

Note: Acid number is also known as acid value, acidity, or neutralization number. Acid number in oils is determined by a titration method in an organic solvent medium (ether or ethanol at an elevated temperature) in which a standard potassium hydroxide solution is used to titrate the acids in oil to a targeted \[pH\] end-point.