450 MILK AND MILK PRODUCTS; DAIRY FARMS 



to the ash, care being taken not to use too much acid, then add a few 

 drops of water, and place a strip of turmeric paper in this water solution. 

 Dry the paper, and if either borax or boric acid is present, a cherry- 

 red color will api)ear. This test is confirmed by moistening the red- 

 dened paper with a drop of an alkali solution, w^hen the paper will turn 

 to a dark olive color, if borax or boric acid is present. 



Test for formaldehyde in milk. 



This test can be performed in connection with the Babcock test. 

 Measure into the Babcock test bottle 17.6 cc. of milk. Add five 

 or six drops of ferric chloride solution and shake thoroughly. Add 

 17.5 cc. of sulfuric acid, but do not mix the acid and milk. If 

 formaldehyde is present, a lavender-colored ring will appear at 

 the point of contact of the acid and milk. If the contents of the 

 bottle are mixed slowly, the entire mass of curd will turn a lavender 

 color. This test will not work if the sample is too old. 



Standardizing milk (Pearson). 



Standardized milk is that which has been changed in its composition 

 to cause it to contain a required amount of fat. This is usually ac- 

 complished by adding cream or skimmed milk. A convenient rule for 

 determining the amount of ingredients to make a mixture testing a cer- 

 tain per cent of fat, is as follows, supposing cream and milk are to be 

 used (in most States it is unlawful to add skimmed milk) : — 



Draw a rectangle, placing the per cent of fat in the cream at the upper 

 left-hand corner, and the per cent of fat of the milk at the lower left- 

 hand corner. Place the desired per cent of fat in the center. The dif- 

 ference between the numbers in the center and at the lower left-hand 

 corner should be written at the upper right-hand corner, and the dif- 

 ference between the numbers in the center and at the upper left-hand 

 corner should be written at the lower right-hand corner. These right- 

 hand numbers represent the proportions of the substances represented 

 at the corresponding left-hand corners, which must be mixed to produce 

 a milk testing the desired amount of fat. 



Thus : To raise the fat test of a 3.8 per cent milk to 4 per cent by the 

 use of cream testing 25 per cent, by completing the figure as explained, 

 it will be seen that for every 21 pounds of 3.8 per cent milk there 

 should be used .2 of 1 pound of 25 per cent cream. 



