A Study of Methods for the Determination of Acidity in Butter Fat

During the past three years, a study of butter made from neutralized cream has received considerable attention hi this laboratory. In connection with this project it seemed possible that valuable information might be obtained by determining the free acidity in the fat phase of the butter. The method employed is based on the general method given by Leathes (3). In addition, the details of the Loathes method for the quantitative separation of free acids from butter fat have be~n worked out because it is desirable at times to obtain these acids free from fat for further study. The following experiments were undertaken in order to check these methods quantitatively and to compare them with the Official method of the A. O. A. C. (1) and the recently described method of Clarke et al. (2). EXPERIMENTAL Reagents and apparatus. Petroleum ether was distilled over solid KOH and the fraction which boiled between 30 and 40 C. was used. Benzene was likewise distilled from solid KOH. Absolute alcohol was refluxed ~ for 1 to 2 hours over solid KOH and aluminum metal (10 gin. of each per liter) and then distilled from these reagents (6). Alcohol so purified was used in the preparation of 0.5 N KOH and C2H~ONa solutions. Indicator. solutions were prepared as follows : 1 gm. of phenolphthalein was dissolved in 100 ml. of absolute alcohol after which alcoholic KOH was added until a faint pink color was produced. Ordinary 95 per cent alcohol was made very slightly alkaline to phenolphthalein with 0.1 N NaOH for the A. O. A. C. method.