256 THE CHEMICAL ANALYSIS OF BUTTER FAT. 



poured back on to the filter till the solution runs through clear ; 

 the barium is estimated as sulphate in 200 c.c. of the clear filtrate. 

 The strength of the barium chloride solution is estimated as 

 sulphate in 10 c.c., and 25 c.c. of the alcoholic soda should be 

 neutralised with hydrochloric acid, evaporated, and the residue 

 taken up with water, and a little barium chloride added ; any 

 precipitate of barium sulphate due to impurities should be 

 deducted from the amount of barium sulphate obtained from the 

 50 c.c. of barium chloride added. 



The barium oxide found in 200 c.c. of the filtrate multiplied 

 by 1-25 is deducted from the barium oxide added in 50 c.c. of 

 solution (corrected, if necessary, for the blank), and the value 

 calculated as milligrammes for 1 gramme of fat. This gives 

 the barium oxide combined with the insoluble fatty acids. The 

 potash absorption is calculated as milligrammes of barium oxide 

 per gramme of fat by multiplying by 1*368, giving the total 

 barium oxide, and the difference between the two values gives 

 the barium oxide combined with the soluble fatty acids. To the 

 last value 200 is added, and the value thus obtained is subtracted 

 from the insoluble value. With butters the difference is always 

 negative, varying from 23-8 to 0-7, and averaging 9-6. 



Other fats and oils give positive values ; coconut oil giving 

 a difference of 38-9 to 45-1, other oils and fats from 46-9 to 50-3. 

 The soluble baryta value usually varies between 50 and 65 for 

 butters, 54-1 to 57-6 for coconut oil, and is very small for other 

 fats. 



Fritzsche speaks well of this method, and shows that even 

 butters low in Reichert-Wollny figures give normal results with 

 the Ave-Lallemant process, and Bolton and Revis also strongly 

 recommend it, but point out that great care must be taken with 

 the analytical technique, especially with the original saponifica- 

 tion titration. 



Estimation of Soluble and Insoluble Fatty Acids. 

 Hehner and Angejll Method. The following method has 

 been adopted by the American Association of Official Agricul- 

 tural Chemists : 



Reagents required. Deci-normal sodium hydroxide. 



Alcoholic potash. Dissolve 40 grammes of good caustic 

 potash, free from carbonates, in I litre of 95 per cent, redistilled 

 alcohol. The solution must be clear. 



Semi-normal hydrochloric acid accurately standardised. 



Indicator. One gramme of phenol-phthalein in 100 c.c. of 

 alcohol. 



About 5 grammes of the sample are weighed into a saponifi- 

 cation flask (250 to 300 c.c. capacity of hard, well annealed glass, 

 capable of resisting the tension of alcohol vapour at 100 C.), 



