STUDY OF MILK. 29 



15. STUDY OF MILK. 



Materials : Pint of fresh, rich milk ; nitric acid and ammonia, 

 Fehling's solution, iodine, caustic soda, osmic acid, vinegar; test- 

 tubes, lactometer, cloth, alcohol-lamp. 



A. Fats. 



Put the milk into a clean glass dish, and al- 

 low it to stand over night. 



1. What layers can be distinguished? 



2. Remove by means of a spoon the top layer 



into a bottle or cup (No. i). 



3. Place a drop of it on unglazed paper. Let 



the paper dry for some time. What 

 kind of nutrient is shown to be present 

 in milk? 

 Nitrogenous substances. 



1 . Boil the rest of the milk ; what change is no- 



ticed? What kind of nutrient is affected 

 in this way by heat? 



2. Remove the scum from the milk and place 



it in a second cup (No. 2). Test a little 

 of it with nitric acid and ammonia. Re- 

 sult? 



3. Add vinegar to the rest of the milk and 



strain through a cloth. What kind of 

 substance is left in the cloth? Test it 

 with nitric acid and ammonia. Result? 

 Place this substance in cup No. 2. 

 Carbohydrates. 



i . Test a small amount of fresh milk with Feh- 



