Vol. Vir. No. 165. 



THE AGRICULTUKAL NEWS. 



271 



PURIFICATION OF COCOA-NUT OIL. 



The preparation of cocoa-nut oil forms a valuable 

 industry both in Trinidad and Jamaica, and various 

 notes and brief articles in relation to methods of 

 preparation, etc., have appeared in past numbers of the 

 AijrtraUardl News (see Vols. II, p. 270 : IV, p. 6). 



After purification, the oil is suitable for use in 

 a variety of ways (such as the preparation of articles of 

 food, as margarine) for which it would not be available 

 in its crude state. The following article dealing with 

 the best methods of purifying cocoa-nut oil appeared in 

 the Philipiilae Journal of t^cienee for February 

 last: — 



Cocoa-nut oil, as it is expressed from copra, which 

 has lieen dried in the sun or by artificial heat, always 

 contains a ijuantity of impurities — oiganic colouring matter, 

 albuminoid bodies and a certain characteristic odonr, 

 all of which are objectionable for particular purpose.s 

 for which the oil is otherwise well suited. While it is 

 quite possible to produce a pure oil directly from the 

 iiuta, if special precaution is taken in curing the latter, the 

 demand for highly refined oil does not seem to warrant the 

 introduction of modern mechanical methods of desiccation at 

 the present time. Hence proces.ses for the i)roduction of pure 

 cocoa-nut oil depend on some subseijuent chemical treat- 

 ment of the commercially expressed oil itself. Clarification 

 by filtration, subsidence, or heating with or without the 

 addition of c(jagulants, is simple and economical of a]iplication 

 and, as generally practised, removes all of the suspended 

 foi-eign matter and most of the soluble impurities, producing 

 a perfectly clear, light, amber oil' of .sufficient purity 

 for .soap manufacture, but it falls short of being completely 

 free from odour and colour. Therefore, further refining 

 constitutes the only known means of producing an odour- 

 le.ss and colourless product suitable for alimental or cosmetic 

 jnu'poses. The removal of the last traces of odour and 

 colour frimi cocna-nut oil presents many difficulties in the 

 "way of subse(pient clarification and risk of loss of oil, and the 

 methods of procedure are necessarily limited to the use of 

 such chemical reagents as are hannless or are themselves 

 easily removable. In general, refining processes may be con- 

 veniently divided into (1) acid and (2) alkaline treatments. 

 The former has not proved applicable for the production of 

 oils for edible, cosmetic, or lidjricating purposes, because of 

 the poisonou.s nature and otherw ise harmful action of mineral 

 acids. The alkaline process makes use of the hydrates or car- 

 bonates of potash or soda, ammonia, caustic lime or magnesia, 

 ■with or without the aid of heat. In purifying cocoa-nut oil by 

 means of alkalies, only the mininuim (ptantity necessary for the 

 purpo.se of neutralizing the free acids present should he used. 

 This amount can be determined accurately by testing the 

 acidity of a small sample of the oil to be refined. If alkali is 

 added in excess, and heating also takes jilace, then the oil 

 itself suffers jiartial decomposition. Care must afso be taken 

 to prevent the formation of an emulsion on adding the alkali 

 solution to the oil, and for this purpose experiments must be 

 carried out to ascertain the concentration of the caustic soda 

 solution which is least likely to bring about the emulsifying 

 effect. 



Ordinary commercial grades of cocoa-nut oil collected 

 on the Manila market contain from 1 ,to 10 per cent, of free 

 fatty acids calculated as oleic acid, and these percentages 

 require approximately 0'15 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 cau.stic liquor 

 previously |irepared. The stronger the caustic liquor used 

 the less the tendency to emulsion formation and the 

 more rapid and complete the action, if projier mechanical 

 devices for thoroughly mixing a strong solution 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 subsidence. The oil ma.y now be steamed and 

 washed with hot water until it is perfectly clear and neutral, 

 and if the above treatment with cau.stic liquor and the 

 subsequent steaming, are pro])erly 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. 



Cocoa-nut oil is also considerably lightened in colour by 

 the above treatment, but in no sense can it be considered 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 acconqilish this 

 conn)letely, it is necessary to subject the refined oil to some 

 nnld bleaching action which does not introduce harmful 

 ingredients which would be difficult of subsequent removal. 

 Of the many well-known methods of bleaching proposed for 

 general use, the use of hydrogen peroxide seems to be most 

 favourable in this regard, as it is easy of applicaticjn, and at 

 its present price is not prohibitive. Sufficient dilute alkali 

 should be added to neutralize any ndneral acid it may 

 contain, and a slight excess of alkali favours the action 

 of the hydrogen peroxide, at the same time having no 

 saponifying action. Next in order of suit- ability is a dilute 

 solution of chloride of lime slightly acidified with acetic 

 acid. If the addition of acid and the temperature of the 

 bleaching are carefully controlled, the chance of injury to 

 the oil by free chlorine is a minimum, and the result is a puic 

 water-white product. 



COWPEAS AND OTHER SOIL-RENOVAT- 

 ING CROPS. 



Farmers' Bulletin -UO of the United States 

 Department of Agriculture contains the following note 

 on the value of cowpeas and other leguminous crops, 

 not only on account of the actual yield obtained, but 

 ;dso through the soil-renovating influence of these 

 crops : — 



Corn reipiires a strong, well-tilled soil, and upon thin 

 land, deteriorated by bad management, the yield ol)tained 

 soon drops below a remunerative average. Such lands will. 

 however, profitably produce other crops of great value for the 

 sustenance of farm stock, and, in addition, the growing of 

 these crops will provide an excellent means of soil renovation. 

 Lands that are now producing 10 bushels of corn per acre 

 will, with much less labour, produce 1 \ tons of co-npea hay 

 per acre, equal in nutritive value to 3 1 bushels of corn ; ov 

 they will yield 1;^ tons (A peanut hay per acre, equal in 

 nutritive value to 23| bushels of corn, and in addition a pea- 

 nut crop of 25 bushels per acre may be secured. 



On rich lands that under good culture will produce 40 

 or more bushels of corn per acre, satisfactory results can be 

 secured by planting cowpeas between the rows of corn. 

 Even rich alluvial soils, estimated to yield 40 bushels of coi'n 

 per acre, if sown to alfalfa, frequently produce 5 tons of hay 

 per acre in a season, equal in feeding value to 106i bushel.'; 

 of corn. In addition, such i;rops as cowpea.s, peanuts, and 

 alfalfa rapidly eiuich the soiL and leave it in excellent mechani- 

 cal condition for the ensuing year. 



