STUDY OF OXYGEN. 5 



2. 'Name the substance produced by the burn- 



ing of each of the above ingredients, and 

 state how each can be recognized. 



3. What are the ingredients of a match that 



will not burn? 



2. STUDY OF OXYGEN. (Dem.) 



Materials : Apparatus-stand, test-tube with perforated stopper, 

 delivery-tube, tray of water, five bottles, a piece of glass to cover 

 each bottle; potassium chlorate, black oxid of manganese, phos- 

 phorus, sulphur, splinters of wood, piece of picture-wire, piece of 

 crayon. 



A. Preparation of oxygen. 



1. Mix a spoonful of pulverized potassium 



chlorate with one-fourth this amount of 

 black oxid of manganese. Put the mix- 

 ture in a test-tube, and attach it to an 

 apparatus-stand in a slanting position. 

 Close the mouth of the tube with a stop- 

 per through which passes a delivery-tube. 

 The other end of the delivery-tube 

 should run beneath the surface of the 

 water in the tray. (See Fig. i.) 



a. Heat the test-tube gently. What do 



you observe? 



b. Potassium chlorate and oxid of man- 



ganese contain a large amount of 

 oxygen. How are these com- 

 pounds made to give up oxygen? 



2. Fill the four bottles with water and cover 



each with a piece of glass. Invert one 

 in the pan of water over the end of the 



