50 Testing Milk and Its Products. 



to it a short piece of fine wire. Manufacturers have 

 improved on this rather crude device and standard 

 measures for calibrating test bottles may 

 now be bought of any dairy supply house 

 (see fig. 19). 



When a test bottle is to be calibrated 

 by this standard measure, it is filled with 

 water to the zero mark on the neck of the 

 bottle. The water adhering to the neck is 

 carefully removed with a strip of blotting 

 paper, and the measure is then lowered 

 into the test bottle, as shown in the illus- 

 tration. If the water rises from to 10 

 on the neck when the upp r point of Ihe 

 measure is submerged in the water, the 

 scale is correct. If greater variations than 

 .2 per cent, occur, the bottle should be re- 

 jected. 



The figure shows one of these calibrator 

 made in two sections, so that the accuracy 

 of the 5 per cent., as well as the 10 per- 

 cent, mark on the scale may he ascer- 

 tained. 



56. The standard measure. In the place 

 of an iron nail, as originally proposed, a 

 FIG. 19. The piece of metal or glass rod may be advn- 



Trowbridge 



calibrator. tageously used as a standard measure. 1 he 

 standardization of this measure is most conveniently 

 done by weighing. Since the specific gravities of iron. 

 copper, brass, and glass are 7.2, 8.7, 8.5, and about 2.7, 

 respectively, pieces of these materials replacing 2 cc. of 



