August, 1908.] 



119 



Oils and Fats. 



PURIFICATION OF COCONUT OIL. 



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 directiy from the nuts if 

 special precaution in curing them is 

 taken, the demand for highly refined oil 

 does not seem to warrant the introduc- 

 tion of modern mechanial 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 im- 

 proved processes for the production of 

 pure coconut oil, refer to some subse- 

 quent chemical treatment of the com- 

 mercially expressed oil itself. Clarifica- 

 tion by filtration, subsidence or heating 

 with or without the addition of -coagu- 

 lants is simple and economical of applica- 

 tion, 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 it 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 ali- 

 mectal or cosmetic purposes. The 

 removal of the last traces of odour and 

 colour from coconut oil presents many 

 difficulties in the way of subsequent 

 clarification and risk of loss of oil, and 

 the methods of procedure are neces- 

 sarily 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, ammo- 

 nia, caustic lime or magnesia, with or 

 without the aid of heat. The efficiency 

 of an alkaline treatment depends upon 

 incomplete saponification, whereby the 

 free, volatile, 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 decom- 

 position and goes to augment the amount 

 of soaps formed. Therefore, unless any 

 alkaline treatment of a vegetable oil is 

 carefully regulated, both as regards the 

 amount of alkali used and the temper- 

 ature employed, low yields of purified 

 oil are obtained. All of the residues 

 or "foots" go to form soap stock, hence the 

 advisability is apparent of employing 

 this process iu conjunction with a mar- 

 ket for the by-product. The main points 

 to note in connection with refining by 

 means of alkalies are, first, the minimum 

 quantity of alkali necessary to effect the 

 purification, and, second, 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. 



Ordinary commerical grades of coconut 

 oil collected on the Manila market con- 

 tain from 1 to 10 per cent, of free fatty 

 acids, calculated as oleic acid, and these 

 percentages require approximately 0"15 

 to l'o 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 caus- 

 tic liquor previously prepared. The 

 strouger the caustic liquor used the less 

 the tendency to emulsion formation and 

 the more rapid and complete the action, 

 if proper mechanical devices for tho- 

 roughly 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 separ- 

 ates 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-de- 

 fined odour of the original oil and to pos- 

 sess the bland, fatty odour of pure melted 

 lard. 



Coconut oil is also considerably 

 lightened in colour by the above treat- 

 ment, but in no sense can it be con- 

 sidered as a colourless oil. To remove 

 the last traces of colouring matter from a 

 vegetable oil is much more difficult than 

 the destruction of the rancid odour, and 

 in order to accomplish this completely it 

 is necessary to subject the refined oil to 

 some mild bleaching action which does 

 not introduce harmful ingredients which 

 would be difficult of subsequent removal. 

 Of the many well-known methods of 



