The Babcock Test. 65 



water. In the latter case the first portions of acid should 

 be added carefully, a little at a time, shaking the bottle 

 after each addition, so as not to cause it to break from 

 the great heat evolved in mixing the acid and the water. 

 Never dilute sulfuric acid by pouring water into it. 



75. If the acid is too weak, correct results may some- 

 times be obtained by using more than the specified 

 quantity, say 20 cc. If a good test is not obtained with 

 this quantity of acid, a new lot must be secured, as its 

 specific gravity in such a case is below 1.82. The ob- 

 serving operator will soon be able to judge of the 

 strength of the acid by its action on milk in mixing the 

 two liquids in the Babcock test bottles; it is indeed re- 

 markable what slight differences in the specific gravity 

 of the acid will make themselves apparent in working 

 the test, as regards the rapidity with which both the 

 curdled milk is dissolved and the mixture of acid and 

 milk turns black. 



76. Strength of sulfuric acid. The relation between 

 the strength of sulfuric acid and its specific gravity will 

 be seen from the following table: 



Strength of Sulfuric Acid (Lunge and Isler, 1890. ) 



Sulfuric Acid Specific Gravity 



(H 2 SO). ( 15 C, water A C). 



97 per cent 841 



96 " 840 



95 " 839 



94 " .837 



93 " 834 



92 " 830 



91 " 1.825 



90 " 1.820 



89 " 1.815 



88 " 1.808 



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