84 



GENERAL SCIENCE 







Melted lead yields a yellow powder called lead oxide. 

 Zinc and magnesium burn brightly with the formation 

 of their oxides. 



When a substance burns with no flame, there is no gas 

 evolved, since a flame is burning gas. Hard coal burns 

 with much less flame than soft coal, indicating the ab- 

 sence of gaseous materials in the hard coal. Coke and 

 charcoal are coal and wood respectively without their 

 gases, which have been driven off by heat. 



Experiment 23. Place a lighted candle in a shallow basin and 

 then lower a tall slender lamp chimney over the candle, supporting 



the chimney by two pieces of 

 wood so that the free passage 

 of air at the bottom of the 

 chimney may not be ob- 

 structed. Now pour water in 

 the basin until the bottom of 

 the chimney is covered and 

 note the action of the flame 

 (Figure 85). 



Oxygen and Life. 



FIG. 85. The candle flame will be ' . 



extinguished when the supply of air is Oxygen IS the llfe-glVing 



principle in the animal 



and vegetable kingdoms, and an abundant supply of it is 

 necessary for the sustenance of life. Neither plants nor 

 animals can live without it. Plants take oxygen from 

 the air through their leaves, while the animals usually 

 have special organs for the purpose of separating the 

 oxygen from the air. The process of obtaining oxygen 

 from the air by plants and animals is called respiration, 

 which consists both of breathing and oxidation in the 

 tissues. In the higher animals the oxygen is taken 

 directly into the lungs, where by osmosis it reaches the 

 blood and is then carried to all parts of the body by 



