46 MODERN METHODS OF TESTING MILK 



ing caused by acid may be remedied by treatment with 

 ammonia, if not too long delayed. Acid on tables, 

 floors, etc., may be neutralized by treatment with 

 washing soda or other alkali. 



METHODS OF TESTING ACCURACY OF 

 APPARATUS 



The correctness of the graduation of the glassware 

 used in the Babcock test is a fundamental condition of 

 accuracy in the results obtained. In some States all 

 graduated glassware used in the Babcock test must 

 be tested by the State and found correct before its use 

 is permitted in commercial operations. Reliable deal- 

 ers guarantee the accuracy of their glassware, and it 

 is found to be much more reliable than formerly. How- 

 ever, it is a safe precaution always to test new appa- 

 ratus before using it. Testing graduated glassware 

 is known technically as calibration. 



Testing or calibrating bottles. In the case of 

 standard milk-testing bottles, the error of graduation 

 should not exceed o.i per cent, at any point of the 

 scale; in the case of standard cream-testing bottles, 

 the error at any point in the scale should not be greater 

 than 0.5 per cent. 



The most reliable method of testing the accuracy of 

 graduated glassware requires an accurate analytical 

 balance with which to weigh out exact amounts of 

 mercury or water (p. 278), but simpler and more rapid 

 methods are available which are sufficiently accurate 

 for practical purposes. Among the methods available 

 for common use are the following : ( i ) Testing with 

 water, (2) use of special tester or plunger, and (3) 

 testing with mercury. 



