Chemical Analysis of Milk and Its Products. 251 



bottle, over the mouth of which a piece of cotton is 

 placed. The milk will filter through, leaving the dirt 

 on the cotton, which is then removed and can be shown 

 to the producer of the milk. 1 



A modification of the apparatus used has been de- 

 scribed in publications of the Wisconsin experiment 

 station. 2 



DETECTION OP PRESERVATIVES IN DAIRY PRODUCTS. 



299. a. Boracic acid (borax, borates, preservaline, 

 etc.). 100 cc. of milk are made alkaline with a soda 

 or potash solution, and then evaporated to dryness and 

 incinerated. The ash is dissolved in water to which a 

 little hydrochloric acid has been added, and the solu- 

 tion filtered. A strip of turmeric paper moistened with 

 the filtrate will be colored reddish brown when dried at 

 100 C. on a watch glass, if boracic acid is present. 



If a little alcohol is poured over the ash to which con- 

 centrated sulfuric acid has been added, and fire is set 

 to the alcohol, this will burn with a yellowish green 

 tint, especially noticeable if the ash is stirred with a 

 glass rod and when the flame is about to go out. 



300. The following modification of the first test given is said 

 to show" the presence of only a thousandth of a grain of borax 

 in a drop of milk (about .15 per cent.) : 8 



Place in a porcelain dish one drop of milk with two drops of 

 strong hydrochloric acid and two drops of saturated turmeric 

 tincture ; dry this on the water bath, cool and add a drop of 

 ammonia by means of a glass rod. A slaty blue color changing 

 to green is produced if borax is present. 4 



1 Hoard's Dairyman, Nov. 29, 1907. 



2 Bull. 195 and Circular 41. 



8 N. J. Dairy Commissioner, report, 1896 p. 36. 

 4 See also par. 151. 



