Important physico-chemical properties of niacin and niacinamide are as follows:
a) Niacin is a white crystalline solid.
b) While niacin is sparingly soluble in water, ethanol and glycerol, niacinamide is readily soluble in water.
c) Niacin is fairly heat stable and can withstand a temperature of 120°C for 20 minutes in acid or alkali. It is one or'the most stable vitamins.
d) Niacinamide is converted into niacin if heated in strong acid or alkali.