This International Standard specifies two methods for determining the solubility of dyestuffs in organic solvents. They are applicable to dyestuffs that do not change chemically under the influence of the solvent and are stable and non-volatile under the specified drying conditions. For volatile solvents (boiling point < 120 °C), the gravimetric procedure is recommended and, for less volatile solvents (boiling point > 120 °C), the photometric procedure is recommended. The choice of procedure should be made on a case-by-case basis. The methods are suitable for concentrations between 1 g and 1 000 g of dyestuff per litre of solvent. Higher concentrations can be used provided the viscosity of the solution is such that the procedure can be carried out readily. The methods are not suitable for the determination of insoluble matter in a dyestuff.