<PICT:0724222/IV (b)/1> <PICT:0724222/IV (b)/2> A fatty acid mixture with components having different melting points is separated into liquid fatty acids and solid fatty acids by separating a dispersion of the fatty acid mixture in an aqueous solution of a capillary active substance at a temperature at which part of the mixture occurs in liquid form and another part of the mixture in solid form by centrifugation into a lighter phase which contains the liquid acids and a heavier phase which contains the solid acids suspended in the aqueous solution of the capillary active substance, the centrifugation being carried out in a centrifuge of the type in which the two phases separate out from one another solely on the basis of their specific gravity and in which no filtering medium such as a screen is employed. The two phases are separately removed from the centrifuge and the aqueous solution separated from the suspended particles of solid fatty acids. The fatty acid mixtures may be obtained from naturally occurring esters of fatty acid mixtures, e.g. esters obtained from land or marine animals or from plants. The fatty acid mixture may also be obtained synthetically, e.g. by the oxidation of natural or synthetic paraffins, or of alcohols such as those obtained by the hydrogenation of carbon monoxide or by the oxidation of the products obtained by addition of carbon monoxide and hydrogen to olefines. Suitable capillary active substances include those containing polyether chains, sulphuric acid semiester groups, sulphonic acid groups and aggregates of free hydroxyl groups such as are present in mono esters of fatty acids or mono ethers of fatty alcohols with tri-, tetra-, penta- or hexahydric alcohols, or the alkylene oxide addition products of such monoesters or monoethers. Other specified capillary active substances are alkylphenol polyglycol ethers, alkyl sulphonates (obtained by reacting an aliphatic hydrocarbon with a mixture of sulphur dioxide and chlorine and saponifying the resultant sulphochlorides), fatty alcohol sulphates and alkyl benzene sulphonates, whilst the fatty acid salts obtained by adding small amounts of basically reacting substances to a mixture of the fatty acids to be separated and water may also be used as the capillary active substance. Water-soluble salts which do not form an insoluble precipitate with the capillary active substance, e.g. alkali metal chlorides or sulphates and water-soluble salts of di- and trivalent metals such as calcium, magnesium or aluminium may be added to the dispersion of the fatty acid mixture in the aqueous solution of capillary active substance. It is preferred to employ a concentration of 0.1-5 per cent of the capillary active substance based on the aqueous solution. If the fatty acid mixture to be separated is a substantially solidified mixture it must first be comminuted by mechanical treatment by pressing through sieves or by using grinding or cutting mechanisms or comminution apparatus whilst if the fatty acid mixture is molten it must be allowed to partially solidify, preferably by cooling down to the temperature at which the separation is to be carried out. The step of allowing the mixture to partially solidify may also be carried out in the presence of additional liquid organic compounds such as hydrocarbons, alcohols, esters or carboxylic acids which should preferably be such as to be easily removed from the fatty acids after the centrifugation. The liquid fatty acids produced by the process are particularly suitable as the additional liquid since the necessity for an additional recovery stage is eliminated in this case. The centrifuge may be of the imperforate basket, tubular or disc type. A suitable type of centrifuge (Fig. 1) comprises a centrifuge basket 11 which is connected with the shaft 12, a supply pipe 13 and discharge pipes 18 and 19. In operation the aqueous solution of capillary active substance is fed through the pipe 13 into the rapidly running centrifuge preferably in such an amount that it is discharged through the pipe 18. The flow of solution is then stopped and the dispersion of the fatty acid mixture in the aqueous solution of capillary active substance is immediately fed into the centrifuge through pipe 13 when it separates into a heavier phase 15 and a lighter phase 16. The heavier phase passes through the slit between a ring 17 and the wall of the centrifuge and is discharged through pipe 18 whilst the lighter phase is removed through pipe 19. In the type shown in Fig. 2 the dispersion is introduced by pipe 21 and the heavier phase centrifuged out through pipe 26 whilst the lighter phase flows through pipe 27 to which is connected a ring 24 and is discharged through pipe 28. In another type (Fig. 3, not shown) the dispersion is fed from below, the heavier phase being discharged through an opening in the upper part of the centrifuge wall whilst the lighter phase is discharged through an opening provided in a portion extending centrally from the top of the centrifuge. The solid fatty acids may be separated from the heavier phase by filtering from the aqueous solution of capillary active substance or by heating to temperatures above the melting points of the solid fatty acids. The separated liquid and solid fatty acids can be separated into further fractions by repeating the centrifugation process at raised or lowered temperature. In an example a synthetic fatty acid mixture made by oxidation of Fischer-Tropsch crude paraffin is heated to 50 DEG C. and after the addition of methanol is slowly cooled to 20 DEG C. while stirring with an aqueous solution of sodium C12-alkyl benzene sulphonate and the resulting dispersion centrifuged in a disc centrifuge into liquid and solid fatty acids. The methanol is separated from the liquid acids whilst the solid acids are separated from the aqueous solution by filtration. Other examples are given for the separation of liquid and solid fatty acids from tallow fatty acids, hardened whale blubber fatty acid, sperm oil fatty acid, fish blubber fatty acid, and from cotton seed and rape seed oil fatty acids (see Group III).ALSO:<PICT:0724222/III/1> <PICT:0724222/III/2> A fatty acid mixture with components having different melting points is separated into liquid fatty acids and solid fatty acids by separating a dispersion of the fatty acid mixture in an aqueous solution of a capillary active substance, at a temperature at which part of the mixture occurs in liquid form and another part of the mixture in solid form, by centrifugation into a lighter phase which contains the liquid acids and a heavier phase which contains the solid acids suspended in the aqueous solution of the capillary active substance, the centrifugation being carried out in a centrifuge of the type in which the two phases separate out from one another solely on the basis of their specific gravity and in which no filtering medium such as a screen is employed. The two phases are separately removed from the centrifuge and the aqueous solution is separated from the suspended particles of solid fatty acids. The fatty acid mixtures may be obtained from naturally occurring esters of fatty acid mixtures, e.g. esters obtained from land or marine animals or from plants. The fatty acid mixture may also be obtained synthetically, e.g. by the oxidation of natural or synthetic paraffins, or of alcohols such as those obtained by the hydrogenation of carbon monoxide or by the addition of carbon monoxide and hydrogen to olefines. Suitable capillary active substances include those containing polyether chains, sulphuric acid semi-ester groups, sulphonic acid groups and aggregates of free hydroxyl groups such as are present in mono-esters of fatty acids or mono-ethers of fatty alcohols with tri, tetra-, penta- or hexa-hydric alcohols, or the alkylene oxide addition products of such mono-esters or mono-ethers. Other specified capillary active substances are alkylphenol polyglycol ethers, alkyl sulphonates, fatty alcohol sulphates and alkyl benzene sulphonates; the fatty acid salts obtained by adding small amounts of basically reacting substances to a mixture of the fatty acids to be separated and water may also be used as the capillary active substance. Water-soluble salts which do not form an insoluble precipitate with the capillary active substance, e.g. alkali-metal chlorides or sulphates and water-soluble salts of di- and trivalent metals such as calcium, magnesium or aluminium may be added to the dispersion of the fatty acid mixture in the aqueous solution of capillary active substance. It is preferred to employ a concentration of 0.1-5 per cent. of the capillary active substance based on the aqueous solution. If the fatty acid mixture to be separated is a substantially solidified mixture it must first be comminuted by mechanical treatment by pressing through sieves or by using grinding or cutting mechanisms or comminution apparatus, whilst if the fatty acid mixture is molten it must be allowed partially to solidify, preferably by cooling down to the temperature at which the separation is to be carried out. The step of allowing the mixture partially to solidify may also be carried out in the presence of additional liquid organic compounds such as hydrocarbons, alcohols, esters or carboxylic acids, which should preferably be such as to be easily removed from the fatty acids after the centrifugation. The liquid fatty acids produced by the process are particularly suitable as the additional liquid since the necessity for an additional recovery stage is eliminated in this case. The centrifuge may be of the imperforate basket, tubular or disc type. A suitable type of centrifuge (Fig. 1) comprises a centrifuge basket 11 which is connected with the shaft 12, a supply pipe 13 and discharge pipes 18 and 19. In operation, the aqueous solution of capillary active sub