Chemical Analysis of Milk and Its Products. 251 



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

 placed. Tim milk will filter through, leavina the dirt 

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

 to the producer of the milk.' 



A modification of the apparatus used has been de- 

 scribed in publications of the Wisconsin experiment 

 station.^ 



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, this will burn with a yellowish green 

 tint, esperially noticeable if the ash is stirred with a 

 glass rod and when the flnme is about to po 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 mUk 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.* 



' Hoard'.s Dairyman, Nov. 20, 1007. 



»Bua. 195 and Circular 41. 



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



' Soi' also par. 151. 



