230 Condensed Milk and Milk Powder 



to one-half its original volume and test with litmus for an alka 

 carbonate. 



FORMALDEHYDE (HEHNBR'S METHOD) 



Dilute the milk with an equal volume of water. Fill a test t 

 one-half full. Add commercial sulphuric acid, specific gravity 1 

 1.84. The acid should be allowed to flow down the side of the t 

 so as to avoid excessive mixing of acid and milk. If formaldeh 

 is present a violet ring forms at the junction of milk and acid, 

 this test the presence of one part of formaldehyde in two hund 

 thousand parts of milk can be detected. When more than .05 

 cent, formaldehyde is present the violet color 'does not appear. 



The same color reaction is obtained when the acid is addec 

 the milk in the Babcock test. 



Farrington and Woll 1 recommend the fallowing meth 

 Measure 5 c.c. of milk in a white porcelain dish, add 5 c.c. of wa 

 and 10 c.c. of hydrochloric acid containing a trace of ferric chloi 

 (Fe 2 Cl 6 ). Heat the mixture. If formaldehyde is present a vi< 

 color appears. 



BORIC ACID AND BORATES 2 



"Render decidedly alkaline with lime water about 25 grams 

 the sample and evaporate to dryness on a water bath. Jgnite 

 residue to destroy , organic matter. Digest with, about 15 c.c. 

 water, add hydrochloric acid, drop by drop, until all is dissoh 

 and add 1 c.c. in excess. Moisten a piece of delicate turmeric pa 

 with the solution; if borax or boric acid is present, the paper 

 drying will acquire a peculiar red color, which is changed by ; 

 monium hydroxid to a dark blue-green, but is restored by acid. 



A preliminary test may be made by immersing a strip of t 

 meric paper in about 100 c.c. of liquid foods, to which about 7 

 of concentrated hydrochloric acid has been added. Solid and p£ 

 goods may be heated with enough water to make them thoroug 

 fluid, hydrochloric acid added in about the proportion of 1 to 

 and tested in the same manner." 



BENZOIC ACID 2 

 "Add 5 c.c. of dilute hydrochloric acid to 50 c.c. of the n 

 in a flask and shake to curdle. Then add 150 c.c. of ether, cork 



1 Farrington & Woll, Testing Milk and its Products 



2 United States Department ol Agriculture, Bureau ol Chemistry, Bulletin 107, 1912 



