go 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, isnow afamiliar article. When heated in 
a dish such butter sputters, with but little foam- 
ing as does oleomargarin, 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. 
50 grams of the sample are melted in a beaker 
at about 50°. Ordinary butter yields a clear 
