DAIRY PRODUCTS. 63 



(2) The elementary analysis of the fats gives no indication whether adulteration has 



been practiced or not. 



(3) Batter fat is not easily decomposed by heat. With a rise of temperature the de- 



composition is at first, for the greater part, confined to the glycerides of the 

 non-volatile acids. 



(4) In the saponification of butter fat by Hehner's method there is no appreciable 



loss of ethers. There is also no loss of volatile acids in direct saponification in 

 alcohol. 



(5) For the detection of foreign fats in butter, the best method is that of Reichert- 



Meissel, and next that of Koettstorfer. 



(6) For a comparative test of the various methods the mean for insoluble acid (Heh- 



uer) is taken at 87.50 per cent. ; for Koettstorfer's equivalent 227, and for Reich- 

 ert-Meissel 28.8. 



(7) The washing out of the soluble acids must not be carried too far ; for 2 to 2.5 



grams of fat three litres of water seem best. 



ABSORPTION OF BROMINE AND IODINE BY BUTTER FATS. 



Oleic acid is capable of absorbing for each formula molecule one mole- 

 cule of bromine or iodine. Stearic acid does not possess this property. 

 Therefore it is easy to approximately determine the relative quantities of 

 these two acids when present in the same fat by the quantity of the 

 halogen absorbed. 



Thus (stearic acid) CioB^C^ does not absorb bromine and iodine, 

 while (oleic acid) does. 



The glycerides of the above acids, i. c., the natural fats, have the same 

 absorptive power as the acids themselves. 



Mills, Snodgrass & Akitt 1 have determined the quantities of bromine 

 absorbed by various fixed oils. The method employed is as follows : 



The weight of dry oil taken is about .1 gram ; this is dissolved in a 

 stoppered bottle of lOOcc. volume by 50cc. dry CC1 4 . To this is now 

 added a solution of about 8 grams per litre of bromine dissolved in C01 4 . 

 The addition of this reagent is continued until apermanent coloration is 

 produced at the end of fifteen minutes. 



If greater accuracy is required an excess of bromine may be added, 

 afterwards treated with a solution of KI and some starch, and titrated 

 with a standard solution of sodium thiosulphate. 



The excess of bromine may also be determined by titratiou with a 

 standard solution of /?-naphthol in C01 4 



Hiibl 2 has described the reactions of fats with iodine. 



The reagents employed are an alcoholic solution of iodine and HgCl 2 , 

 in the proportion 1 2 : Hg01 2 . 



The iodine is dissolved (25 grams) in absolute alcohol (500ce.) The 

 mercuric chloride is also dissolved (30 grams) in nearly absolute alcohol 



1 Journ. Soc. Chem. Industry, vol. 2, p. 435, and vol. 3, p. 366. 



2 Ding. Poly. J., vol. 243, p. 281. 



