44 LIVING MATTER OR PROTOPLASM. 



C. Carbohydrates. 



1. Mount a little powdered starch (potato starch if possible) 

 in water, examine with the microscope, and run in dilute iodine 

 solution. The blue color thus produced is a characteristic reaction 

 for starch (C 6 H 10 O 5 ). 



2. Make a number of sections of some succulent vegetal stem ; 

 e.g., stem of Pelargonium. Place them for a few minutes in 

 strong iodine solution, wash with water, and transfer to strong 

 sulphuric acid (2 parts acid, 1 part water, by volume). Mount 

 the sections in the acid, and examine. In successful experiments 

 the cell-walls become blue a characteristic reaction for cellulose 



(C.H..O.). 



3. Make in a test-tube a very dilute solution of glucose or 

 grape-sugar (C 6 H 12 O 6 ) ; add a drop or two of a weak solution of 

 cupric sulphate (CuSO 4 ), then several drops of a solution of so- 

 dium or potassium hydrate (KOH), and boil the fluid. A reddish 

 precipitate of cuprous oxide is formed as follows : 



CuSO 4 + 2KOH K,SO 4 + Cu(OH), 



Cupric sulphate. Potassic hydrate. Potassic sulphate. Cupric hydrate. 



On heating in the presence of glucose, the cupric hydrate is 

 reduced to cuprous oxide (Cu 2 O). This is known as " Trorn- 

 mer's test" for glucose. 



D. Fats. 



1. Shake up some olive oil with water in a test-tube. Note 

 that they do not mix. 



2. Repeat the experiment, using diluted white-of-egg instead 

 of water. The fluid becomes milky white. Examine with the 

 microscope, and observe that the oil is broken up into minute 

 drops. The fat has been "emulsified" and the mixture is an 

 emulsion. 



3. Mount some milk (which is likewise an emulsion). Exam- 

 ine with the microscope, and compare with (2). 



4. Add strong alcohol to some oil in a test-tube. They do 

 not mix. 



5. Heat the test-tube. The fluids mix completely. Upon 

 cooling the oil separates and the fluid becomes turbid. 



