410 



[November, 1908. 



OILS AND FATS. 



PURIFICATION OF COCONUT OIL. 



Simple Methods. 

 Coconut oil, as it is expressed from 

 sun or grill-dried copra, always contains 

 a quantity of impurities— organic 

 colouring matter, albuminoid bodies 

 and a certain characteristic-odour, 

 all of which are objectionable for 

 particular purposes for which the 

 oil is otherwise well suited. While it 

 is entirely possible to produce a pure 

 oil directly from the nuts if special 

 precaution in curing them is taken, 

 the demand for highly-refined oil does 

 not seem to warrant the introduction 

 of modern mechanical methods of 

 desiccation at the present time, hence 

 the numerous patents which are taken 

 out from time to time, and the frequent 

 notices in the literature of new or 

 improved processes for the production 

 of pure coconut oil, refer to some 

 subsequent chemical treatment of the 

 commercially expressed oil itself. Clari- 

 fication by filtration, subsidence or 

 heating with or without the addition 

 of coagulants is simple and economical 

 of application, and, as generally 

 practised, removes all of the suspended 

 foreign matter and most of the soluble 

 impurities, producing a perfectly clear, 

 light, amber oil of sufficient purity 

 for soap stock, but ib falls short of 

 being completely free from odour and 

 colour. Therefore, further refining 

 constituents, the only known means of 

 producing an odourless and colourless 

 product suitable for alimental or cos- 

 metic purposes, are necessary, 



Refining Processes. 

 The removal of the last traces of 

 odour and colour from cocount oil 

 present many difficulties in the way 

 of subsequent clarification and risk of 

 loss of oil, and the methods of procedure 

 are necessarily limited to the use of 

 such chemical reagents as are harmless 

 or are easily removed. In general, 

 refining processes may be conveniently 

 divided into (1) acid, and (2) alkaline 

 treatments. The former has not proved 

 applicable for the production of oils 

 for edible, cosmetic or lubricating 

 purposes, because of the poisonous 

 nature and otherwise harmful action 

 of mineral acids. The alkaline process 

 makes use of the hydrates or carbonates 

 of the fixed alkalies, ammonia, caustic 

 lime or magnesia, with or without the aid 

 of heat. The efficiency of an alkaline 

 treatment depends upon incomplete 

 saponification, whereby the free, volite, 



fatty acids, which are responsible to a 

 large measure for the characteristic 

 odour of coconut oil, are first neutralized 

 and precipitated as a salt of whichever 

 alkali is employed. If the alkali be 

 added in excess of the amount necessary 

 to neutralize the free acids, and the oil 

 is steamed or otherwise heated, then 

 the neutral glycerides — that is the oil 

 itself — suffers partial decomposition and 

 goes to augmeut the amount of soaps 

 formed. Therefore, unless any alkaline 

 treatment of a vegetable oil is carefully 

 regulated, both as regards the amount 

 of alkalie used and the temperature 

 employed, low yields of purified oil are 

 obtained. All of the residues or "foots " 

 go to form soap stock, hence the advi- 

 sability is apparent of employing this 

 process in conjunction with a market 

 for the by-product. The main points to 

 note in connection with refining by 

 means of alkalies are, first the miuimum 

 quantity of alkali necessary to effect the 

 purification ; and, secondly, the right con- 

 centration of caustic lye which is un- 

 favourable to the formation of emulsions. 

 The minimum quantity of alkali can be 

 determined accurately by testing the 

 acidity of a small sample of the oil to be 

 refined or by the cut and dried methods 

 of practical experience. 



Free Fatty Acids. 



Ordinary commercial grades of coconut 

 oil contain from 1 to 10 per cent, of free 

 fatty acids calculated as oleic acid, and 

 these percentages require approximately 

 O'lo to 1*5 parts, respectively, of caustic 

 soda per 100 parts of oil. The caustic 

 soda may be added to the oil either in 

 the solid state with subsequent addition 

 of water, or better in the form of a 

 caustic liquor previously prepared. The 

 stronger the caustic liquor used the less 

 the tendency to emulsion formation, and 

 the more rapid and complete the 

 action, if proper mechanical devices for 

 thoroughly mixing a strong lye with the 

 oil are used. If, after the addition of 

 the caustic the oil is gradually heated to 

 the boiling point of water, the soap 

 separates in a granular condition and is 

 easily removed by filtration or sub- 

 sidence. The oil may now be steamed 

 and washed with hot water, until it is 

 perfectly clear and neutral, and, if the 

 above treatment with caustic liquor and 

 the subsequent steaming are properly 

 conducted, the resulting oil will be found 

 perfectly free from the well-defined odour 

 of the original oil and to possess the 

 bland, fatty odour of pure melted lard, 



