90 MILK PRODUCTS 



Index of Refraction. — This datum differs nota- 

 bly in different oils, but it is not of much value 

 in detecting adulteration unless considerable of 

 the adulterant be present. Several instruments 

 have been devised for making refraction de- 

 termination; a familiar one is the butyrorefrac- 

 tometer of Zeiss. 



The butyrorefractometer has been strongly 

 recommended for the examination of butter. 

 It is equally adapted for the general examination 

 of fats and oils, and may be used for the de- 

 termination of the index of refraction as well. 

 As these instruments are made by only one firm 

 and are furnished with directions for use, further 

 description will not be required. 



Renovated Butter. — So-called "process" or 

 "renovated" butter, made by melting old or in- 

 ferior samples, purifying the fat, coloring and 

 salting, is now a familiar article. When heated in 

 a dish such butter sputters, with but little foam- 

 ing as does oleornargarin, but yields with alcoholic 

 solution of sodium hydroxid the pineapple odor. 

 The fat or process butter gives refractometric 

 data and Reichert-Meissl data similar to ordinary 

 butter. Hess and Doolittle state that the curd 

 of process butter has characteristic qualities, and 

 propose the following method for detecting it. 



SO grams of the sample are melted in a beaker 

 at about 50°. Ordinary butter yields a clear 



