G4 



FOODS AND FOOD ADULTERANTS. 



(500cc.). After filtering it is added to the solution of iodine. After stand- 

 ing twelve hours its iodine strength is determined by titration with deci- 

 normal solutions of sodium thiosulphate. From .8 to 1 gram of the fat is 

 dissolved in lOcc. chloroform. To this, in a stoppered bottle, is added the 

 solution of iodo mercuric chloride (20 to 30cc.) After standing for two 

 hours the solution must still be brown. 



Add now 10 to 15cc. 10 per cent, water solution of KI and dilute with 

 water to 150cc. The free iodine is then determined by standard thio- 

 sulphate of sodium. The compound formed when pure oleic acid is 

 treated as above is chloro-iodo-oleic acid (Oj 8 H3 4 IClO 2 ). 



Moore 1 has tried Hlibl's method and finds it valuable. 



The fat of butter containing less oleic-glycerides than the fats ordi- 

 narily used as adulterants for butter shows, consequently, less bromine 

 or iodine absorption : 



The method is therefore of value in determining the nature of the fat 

 under examination. 



If there be a mixture of two fats the methods will also give a fairly 

 good approximation of the percentages of each. 



Thus, let x be the percentage of one fat and yof the other. 



Then 



x+y=WO 



Let m be the representative of the iodine absorption of x and n of y, 

 and let A be the number found for the mixture. 

 Then 



100 (A n) 

 m n 



Jones 2 points out the changes which butter fats undergo when kept 

 for a long while at a high temperature. He notices in a few hours that 

 the specific gravity of such a fat kept at 100 F. increased from 912.1 

 to 912.G. He uses the following method of estimating the insoluble fatty 

 acids : 



KEAGENTS. 



(a) Twenty-eight grains roughly weighed of the best potassium hydrate dissolved to 



a litre with alcohol, specific gravity .840. 



(&) Twenty-five grains of strong sulphuric acid made up to a litre of distilled water, 

 (c) Decinormal soda solution of exact strength. 



Sapouification is carried on in flasks about 250cc. capacity. About 5 

 grams of butter fat arc used for each saponification. The alcoholic 



1 Am. Chcm. Jour., vol. (>, p. 416. 



2 Analyst, 1878, pp. 19 cl seq. 



