METHODS OF TESTING THE ACIDITY OF MILK 145 



will be more intense in proportion as there is less acid. 

 Any other measure may be usd in place of the brass 

 cartridge-shell, but in every case care must be taken 

 to use equal amounts of milk or cream and of alkali 

 solution. 



Publow's method (Fig. 39a) is fully described in 

 Circular No. 7, Cornell University Experiment 

 Station, 1909. The alkali solution is tenth-nor- 

 mal, prepared by diluting 50 cc. of a special 

 solution (containing 9.2 grams of pure caustic 

 soda) to 2300 cc. In making the test a 9-gram 

 sample is used, the test being carried out in the 

 usual way. The burette used 

 holds 10 cc. Each cubic centi- 

 meter of alkali solution used 

 represents o.i per cent, of acid 

 in the material tested. 



Marschall's method like Pub- 

 low's uses a 9~cc. sample and a 

 tenth-normal solution of alkali, 

 (called "neutralize!-"). The 

 characteristic feature of the FIG 39 _ CONVENIENT 

 method is a combined burette and APPARATUS FOR ACIDITY- 

 bottle for holding the alkali solu- TESTING 



tion (Fig. 39b). The burette is 

 graduated to 0.2 cc. The reading represents o.i per 

 cent, of acid for each cubic centimeter of alkali solu- 

 tion used. The alkali is also furnished in dry form in 

 connection with this test, the contents of one package 

 making 1000 cc. of tenth-normal alkali. 



Manns' method uses a so-called "neutralizer," which 

 is simply a tenth-normal solution of sodium hydroxide 



