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. — loo grams of sodium hydrox- 

 id are dissolved in loo 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 looo 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 2i2°F. 



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 I45°F 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 



