This International Standard specifies a method for the determination of the viscosity number of dilute solutions of polyamides in certain specified solvents.Polyamide samples must be completely soluble in the solvents mentioned. Additives such as flame-retardants and modifiers often interfere with the viscosity measurement, having an increasing effect on the viscosity number in formic acid and a decreasing effect on the viscosity number in sulfuric acid. The extent of the effect for polyamide compounds depends on the additive, the quantity of the additive, the presence of other additives and the compounding conditions.For pure polyamides or polyamides conta