50 



Testing Milk and Its Products. 



tion of the neck of a milk test bottle is measured with a 

 piece of metal which is carefully filed to such a size that 

 it will displace exactly two cubic centimeters of water. 

 He used a thirty-penny wire nail, cutting off the head 

 of the nail and attaching to it a short piece of fine wire. 

 Manufacturers have improved on this rather crude de- 

 vice and standard measures for calibrating ^~n 

 test bottles can now be bought of dairy v^ 

 supply houses (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 upper point of the 

 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 calibrators 

 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 be ascer- 

 tained. 



56. The standard measure. In the place 

 of an iron nail, as originally proposed, a 

 piece of metal or glass rod may be advan- Trowbridge caf- 

 tageously used as a standard measure. The 

 standardization of this measure is most conveniently 



