70 MILK PRODUCTS. 



The method of determining the volatile acids of but- 

 ter-fat, adopted by the Association of Official Agricul- 

 tural Chemists, is as follows : 



Caustic soda solution. 100 grams of sodium hydrox- 

 id are dissolved in 100 c. c. of pure water. It should 

 be as free as possible from carbonates, and be pre- 

 served from contact with the air. 



Alcohol, of about 95 per cent., redistilled with caustic 

 soda. 



Acid. Solution of sulfuric acid containing 25 c. c. of 

 strongest acid in IOOO c. c. of water. 



Barium hydroxid. An accurately standardized, ap- 

 proximately decinormal solution of barium hydroxid. 



Indicator. Alcoholic solution of phenolphthalein. 



Saponification flasks, 250 to 300 c. c. capacity, of hard 

 well annealed glass, capable of resisting the tension of 

 -alcohol vapor at 2I2F. 



A pipette, graduated to deliver 40 c. c. 



Distilling apparatus. 



Burette. A accurately calibrated burette, reading 

 to tenths of a c. c. 



Weighing the fat- The butter or fat to be examined 

 should be melted, and kept in a dry warm place at 

 about I45F for two or three hours, until the moisture 

 .and curd have entirely settled out. The clear super- 

 natant fat is poured off and filtered through dry fil- 

 ter paper in a jacketed funnel containing boiling water. 

 Should the filtered fat in a fused state not be perfectly 

 clear, the treatment above mentioned must be repeated. 



The saponification flasks are prepared by having 



