4(3g Philippine Journal of Science 1919 



Equal parts of the oil and the reagent were shaken for five 

 seconds in a test tube and allowed to stand two minutes. The 

 colors so produced were, for purposes of comparison, divided 

 into five classes: 1, pale pink; 2, pale violet; 3, medium violet; 

 4, deeper violet ; 5, intense violet. 



Oxidizability value. — This comparatively new determination 

 was used for confirming rancidity in various oils by Issoglio, 11 

 who states that edible oils and fats give values of from 3 to 10, 

 while a value above 15 indicates rancidity. From the results 

 of Brill and Parker 12 it appears that 15 is much too high for a 

 sweet coconut oil, but that the test has some value. 



For the purposes of the present study it was necessary to 

 modify Issoglio's method somewhat, both because the quantities 

 of oil available were insufficient to supply the 20 to 25 grams 

 demanded by his procedure, and because his method, which uses 

 only one-tenth of the distillate for titration, unduly increases 

 the experimental error. The modified determination was as 

 follows : 



About 5 grams of oil and 100 cubic centimeters of recently 

 boiled water were placed in a 500 cubic centimeter distilling 

 flask. The side arm of this flask had been bent in the middle 

 at an angle of about 120°, so that when attached to an ordinary 

 Liebig condenser the neck of the flask was inclined, and the 

 first half of the side arm had sufficient slope to allow any 

 mechanically carried oil to drain back into the flask. The flask 

 was heated, and steam, generated from recently boiled water, 

 was passed through at a rate that gave 100 cubic centimeters 

 of distillate in ten minutes. The 100 cubic centimeters of 

 distillate were treated with 10 cubic centimeters of 20 per cent 

 H 2 S0 4 and 25 cubic centimeters of 0.02 N KMn0 4 , then heated 

 to boiling, and boiled five minutes in a 300 cubic centimeter 

 Erlenmeyer flask with a small funnel inserted in the neck. An 

 ebullator tube 13 was used, both to keep the temperature con- 

 stant, and to prevent loss of vapor by bumping. The flask was 

 allowed to cool to about 70°, and 25 cubic centimeters of 0.02 N 

 oxalic acid were added. The excess oxalic acid was titrated 

 against KMn0 4 . The oxidizability value, or the number of 



"Issoglio, G., Ann. chim. applic. 6 (1916) 1-18. Chem. Abs. 10 (1916) 

 2943. 



12 Philip. Journ. Sci. § A 12 (1917) 106. 



13 A piece of 5 millimeter tubing, long enough to stand upright in the 

 flask, sealed at the upper end and about 15 millimeters from the lower end. 



