Chemical Analysis of Milk and Its Products. 247 



and weighed. A quart of milk or cream should not 

 give any visible sediment on standing for several hours. 

 A very simple and striking method of showing dirt 

 in milk has been suggested by Gerber. About a pint of 

 milk is poured into an inverted bottomless long-necked 

 bottle, over the mouth of which a piece of linen is tied. 

 The milk will filter through this cloth, leaving the dirt 

 en it. When the milk has run through, the cloth is 

 taken off and can be shown to the producer of the milk. 1 



DETECTION OF 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; after a little while 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.) :* 



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

 strong hydrochloric acid and two drops of saturated turmeric 



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



2 N. J. Dairy Commissioner, report 1896, p. 37. 



