ON MILK AND MILK-TESTING 8l 



3. Formaldehyde. 



4. Benzoates and benzoic acid. 



5. Carbonate and bicarbonate of soda. 



6. Salicylic acid. 



How may the presence of peroxides in milk be de- 

 tected? 



Add to 15 or 20 c. c. of milk in a milk test bottle 

 or test tube a quantity of paraphenylenediamin 

 hydrochlorid the size of a pea and shake the mix- 

 ture vigorously for five or ten seconds. If per- 

 oxides are present the milk will turn blue within 

 a few minutes. When the blue solution is made 

 alkaline the color changes to a yellowish light red. 

 If the peroxide has been in the milk for a long time, 

 the test may not work well. 



How may borax or boric acid in milk be detected? 



To 50 c. c. of the milk add enough sodium hydrate 

 to make alkaline. Evaporate the solution to dry- 

 ness and incinerate. Acidify the ash with a small 

 amount of strong hydrochloric acid. A strip of 

 tumeric paper is then soaked in the solution for a 

 few minutes -and afterward dried on a clean glass 

 or porcelain surface. If the paper when dry is a 

 reddish color and turns to a dark olive green on 

 the addition of dilute ammonia, the presence of 

 boric acid or borates is assured. 



How may the presence of formaldehyde in milk be 

 detected? 



To 15 or 20 c. c. of milk in a Babcock milk test 

 bottle or in a test tube add 4 or 5 drops of a 10 per 

 cent solution of ferric chlorid. Then add a volume of 



