FOODS 91 



now contains all the insoluble volatile fatty acids which 

 have distilled over. These are dissolved in alcohol, and 

 the solution is titrated with N /io baryta + phth. The 

 number of c.c. required is called the " new butter value " 

 of the fat. This varies with the Reichert figure, being 1-3 

 where the Reichert is 20, and 3-0 where the Reichert is 30. 

 An increase of o-i in the new butter value corresponds to 

 an addition of i per cent of coco-nut oil. The mode of 

 calculation is thus : The new butter, value of a pure 

 butter having the same Reichert figure is subtracted 

 from the new butter value of the sample. The difference 

 multiplied by io gives the percentage of coco-nut oil 

 present. Ten per cent and under is not detectable with 

 certainty. (See article on " The Estimation of Coco-nut 

 Gil in Butter-fat," by F. W. Harris, F.I.C., in the Analyst, 

 November, 1906.) 



Insoluble or Fixed Fatty Acids. About 5 grm. of the 

 fat are taken in a flat porcelain dish or in a flask, melted on 

 the water-bath, and 50 c.c. of methylated spirit or absolute 

 alcohol added. A clear yellow solution is formed. Now 

 add 2 grm. of NaOH or KOH, and continue the heating, 

 stirring all the while. The fats are saponified. In five 

 minutes add a few drops of water ; if turbidity ensues, all 

 the fat has not been saponified ; continue the heating. 

 Repeat until no turbidity ensues. (If too much water is 

 added, some of the fat may be precipitated from solution. 

 In that case add more alcohol.) Continue to heat until all 

 the alcohol is evaporated and a jelly of soap remains. 

 Then add water, almost filling the dish, and in this the soap 

 dissolves. Dilute HC1 is now added until strongly acid, 

 and the fatty acids are thus liberated. Heat for half an 

 hour on the water-bath, filter through a weighed filter- 

 paper (5 inches diameter) placed in a hot-water jacket, 

 washing all the fatty acids from the dish with repeated 

 amounts of boiling water, until the filtrate is no longer acid. 

 The insoluble fatty acids remain on the filter-paper. They 

 are solidified by putting cold water in the jacket. The 

 paper is then carefully removed, placed in a small 

 weighed beaker, and dried for two hours, and then the 

 beaker and contents are weighed. The percentage of 

 insoluble fatty acids in the butter fat is then calculated, 



