27 Oils and Fats. 



proposed to remove these defects, is based on the simultaneous action of phloro- 

 glucine and resorcine in an acid medium ; the sensitiveness and certainty of the 

 reaction is diminished if only one of these substances is employed. Both phloro- 

 glucine and resorcine have been proposed for testing the purity of olive oil, but 

 the results obtained did not offer any great certainty, olive oil having a very similar 

 composition to seed oils, and even giving doubtful reactions itself, while old 

 seed oils, or those changed by a preliminary refining produced no colouration at 

 all. This is not the case with copra oil, because it only contains about one-tenth 

 of non-saturated liquid glycerides, whereas seed oils and olive oil have about 

 nine-tenths, being in consequence much more sensitive to the action of the reagents. 



Mode of Operation.— The temperature of the reagents and the oil should be 

 10-12 deg. C; the oil should be clear and free from water ; if necessary, it should be 

 filtered. Pure 40 deg. nitric acid is required free from nitrous oxides ; a freshly 

 opened bottle is best. The phloroglucine and resorcine should be quite pure, 

 of recent preparation, and protected from the warmth and vapours of the laboratory. 

 The saturated solutions should be made the same day, employing perfectly pure 

 ether and benzine. It is needless to add that all apparatus used should be ' 

 scrupulously clean. Having taken these precautious 4 c.c. of the copra oil are 

 placed in a 15 c.c. graduated tube, and 2 c.c. of the saturated solution of phloro- 

 glucine in ether added ; when dissolved 2 c.c. of the solution of resorcine in 

 benzine are added. The tube is then immersed in water at about 10 deg. C, care 

 being taken that not the least drop enters the tube ; it is then withdrawn 

 and 4 c.c. of nitric acid (40 deg ) added. The whole is then transferred into a 

 clean test tube and violently agitated for five seconds ; if no reaction is produced 

 the contents of the tube are well shaken up at intervals, attentively observing 

 the oil all the while. 



Copra oil remains perfectly clear and is practically unaltered, negligible 

 traces of impurities give a rose tint, hardly perceptible and rapidly disappearing. 

 The addition of any seed oil, such as arachis, sesame, cottonseed, poppy seed 

 rape, castor, etc., in the proportion of 5 per cent, and more, produces a bright 

 red colouration, quite characteristic, which remains some seconds. Tallow and 

 the oleonaphthas give the same colourations. Olive oil also produces the reaction, 

 although less perceptibly ; the process cannot, therefore, be used for determining 

 its purity. Pure butter and lard are not affected, and consequently the presence 

 of tallow or seed oils can be detected in these bodies by this test, but with 

 less certainty and sensitiveness than in coprah. It is not necessary to take into 

 account the reactions which are subsequently produced under the prolonged 

 action of pure nitric acid. In short, copra oil can be rapidly tested by this 

 method, which responds to the needs of' the numerous industries in which it is 

 used so largely ; it is distinct, sensitive and can be applied in a few minutes- The 

 determination of the constants has always agreed with the indications it has 

 given. It is as well to carry out a second test simultaneously in which 5 per 

 cent, of arachis oil has been added to copra oil for comparison. 



The action of pure hydrochloric acid and fresh sesame oil : — It is well 

 known that old or altered seed oils do not give the same reactions as the fresh 

 oils. Cottonseed oil which has been heated, for example, does no longer 

 reduce silver nitrate. The process just described preserves the same value in 

 all cases. If the intermixture is made in sensitive proportions the presence of 

 an altered oil in copra oil can be detected by pure hydrochloric acid, after 

 adding fresh sesame oil. Thus a cottonseed oil, insensible to the ordinary reactions 

 is mixed with _ the copra oil, and, after ascertaining that the phloroglucine- 

 resorcine reaction has not lost its insensity, fresh sesame oil is added to the 

 same mixture, and the whole shaken up with an equal volume of pure hydro- 

 chloric acid. In a few seconds the acid layer acquires a fine characteristic green 

 colour. Old or altered sesame oil, which does not become red by the action of 

 hydrochloric acid in the presence of sugar or furfurol, gives a green colouration 

 by the addition of fresh sesame oil and pure hydrochloric acid. Pure, old, or 

 altered copra oil is not sensitive to this reagent.— Les Carps Gras IndustrieLs* 



