1416 FOODS AND FOOD ADULTERANTS. 



ZEISS BUTYRO-REFRACTOMETER. a 



Place the instrument upon a table where diffuse daylight or any 

 form of artificial light can be readily admitted for illumination. Sup- 

 ply through nozzle D a stream of water of constant temperature. 

 Then open the prism casing by giving to the pin F a half turn. The 

 surfaces of the prism must now be cleaned with the greatest care, 

 which is best done by applying soft linen moistened with ether. Now 

 melt the sample of fat and pour the clear fat through a filter, allowing 



FIG. 2. Zeiss's butyro-refractometer. 



the first two or three drops to fall on the surface of the prism con- 

 tained in casing B. For this purpose the apparatus should be raised 

 with the left hand, so as to place the prism surface in a horizontal 

 position. Then press B against A and bring F back into its original 

 position by turning it in the opposite direction. Adjust the mirror 

 until it gives the sharpest reading. If the reading be not distinct 



a Wiley, Prin. and Prac. Agr. Anal., vol. 3, pp. 339-341. Also description by 

 manufacturer. 



