The Babcock Test. 



63 



Babcock testers run by electricity have lately been 

 put on the market by a couple of manufacturers (fig. 

 25). Where no 

 steam, but elec- 

 trical current is 

 available, these 

 machines may 

 be installed to 

 great advantage, 

 as they are con- 

 venient to use 

 and may be de- 

 pended on to 

 run at the re- 

 quired speed. 

 Some provision 

 for getting hot 

 water must be at hand in using electrical Babcock testers. 1 



3. SULFURIC ACID. 



72. The sulfuric acid to be used in the Babcock test 

 should have a specific gravity of 1.82-1.83. 2 Commer- 

 cial sulfuric acid (sometimes called oil of vitriol] is 

 always used; it can be bought for about 2 cents a 

 pound in carboy lots and 25 cents or less. a quart at re- 

 tail. One quart of acid is sufficient for fifty tests. The 

 acid should be kept in glass bottles or jugs, prefer- 

 ably glass or rubber stoppered ones, since a cork stop- 



1 The method of installation of a 40-bottle electrical Babcock tester is 

 described in detail in Kept. Dept. of Health, City of Chicago, 1906, p. 18. 



2 A specific gravity of 1.82 means that a given volume of the acid 

 weighs 1.82 times as much as the same volume of water at the same 

 temperature (see also under Lactometer, 109). 



FIG. 25. Type of Babcock electrical testers. 



