11 



pressure is available, a steam turbine tester is strongly 

 recommended for the reason that it maintains a uniform 

 motion under a definite pressure and at the same time the 

 steam keeps the bottles warm and supplies the hot water 

 required. Whatever kind of tester is used, it must be 

 firmly secured to a rigid support. There must be no 

 shaking or trembling of the tester when in motion. 



Acid. The acid used in the Babcock test is the commer- 

 cial sulphuric acid, sometimes called oil of vitriol, and 

 should have a specific gravity of between 1.82 and 1.83. 

 It should be kept in glass bottles or jugs, preferably with 

 glass stoppers. Rubber stoppers will last for a time, but 

 the use of cork stoppers is not permissible, as cork is rapidly 

 attacked by the acid. Owing to the property of sulphuric 



FIG. 7. A dipper made entirely of glass and holding 17.5 cubic centi- 

 meters for measuring acid in the Babcock test. 



acid of absorbing water from the air and thus diluting 

 itself, it can not be kept in open containers. 



Sulphuric acid is an extremely corrosive liquid, which 

 attacks the skin, the clothing, wood, and most of the com- 

 mon metals. Should the acid be spilled on the clothing, 

 it should be immediately washed off with plenty of water, 

 and ammonia water applied; this in turn must also be 

 washed off. Unless the acid is washed off immediately 

 after contact with the skin, severe burns will result. Acid 

 spilled on the table or floor may be neutralized with wash- 

 ing soda or other alkali. Lead is the only common metal 

 not attacked by this acid. If much testing is to be done, 

 it is a good plan to cover the testing table with sheet lead. 



Testing strength of acid. As already mentioned, the 

 specific gravity of the sulphuric acid used should be 

 between 1.82 and 1.83. It is much better to purchase it 

 guaranteed of the proper strength than to bother with 

 diluting the stronger acid. Creamery supply houses han- 



