30 LABORATORY EXERCISES. 



ling's solution. Result? (Milk-sugar or 

 lactose sometimes gives the test with 

 Fehling's solution like grape-sugar.) 

 2. Test milk with iodine. Is starch present? 



D. Specific gravity of milk. 



1. Pour some good rich milk into a tall glass 



jar. Test it with a lactometer and re- 

 cord specific gravity. 



2. Set the milk aside to allow the cream to 



rise. Remove the cream and test the 

 skim -milk with the lactometer. 



a. What change in specific gravity do 



you note? 



b. Explain this change. 



3. Determine the specific gravity of a second 



portion of milk. Dilute the milk with 

 water and again find specific gravity. 

 (Fresh unskimmed milk usually has a 

 specific gravity of 1028 to 1034.) How 

 can adulteration of milk be detected? 



E. Microscopic examination of milk. (In class.) 



1. Place a drop of milk on a clean glass slide, 



and cover with a cover-glass. Examine 

 under the compound microscope. 



a. What is the appearance of the oil- 



globules ? 



b. Are they all of the same size? (The 



fat in milk is said to be in a state of 

 emulsion, each tiny sphere being 

 surrounded by a thin covering of 

 albumin.) 



2. Place a drop of dilute caustic soda at the 



