MATCHES 51 



with a one-hole rubber stopper in which is fitted a long, narrow 

 tube, and clamp the test tube to an iron support as shown in 

 Figure 26. Fill the trough with water until the shelf is just 

 covered and allow the end of the delivery tube to rest just 

 beneath the hole in the shelf. Fill a medium-sized bottle with 

 water, cover it with a glass plate, invert the bottle in the 

 trough, and then remove the glass plate. Heat the test tube 

 very gently, and when the gas bubbles out of the tube, slip the 

 bottle over the opening in the shelf, so that the tube runs into 

 the bottle. The gas will force out the water and will finally 



FIG. 26. Preparing oxygen from potassium chlorate and manganese dioxide. 



fill the bottle. When all the water has been forced out, slip 

 the glass plate under the mouth of the bottle and remove the 

 bottle from the trough. The gas in the bottle is oxygen. 



Everywhere in a large city or in a small village, smoke is 

 seen, indicating the presence of fire; hence there must exist a 

 large supply of oxygen to keep all the fires alive. The supply 

 of oxygen needed for the fires of the world comes largely from 

 the atmosphere. 



Matches. Material is ordinarily set on fire by matches, 

 thin strips of wood tipped with sulphur or phosphorus, or both. 

 Phosphorus can unite with oxygen at a fairly low temperature, 

 and when phosphorus is rubbed against a rough surface the 



CLARK INTRO. TO SC, 4 



