Specifies a method for the preparation of the water-insoluble fatty acide and determination of their solidification temperature. The method is not applicable to titres below 30 degrees centigrade. The principle is saponification of a test portion with potassium hydroxide solution in glycerol, dissolution of the soap in water and neutralization. Washing of the separated insoluble fatty acids with hot sodium chloride solution, drying and filtering. Melting of the prepared fatty acids, cooling them, with continuous stirring, and observation of the solidification temperature.