RESPIRATION. IOI 



EXPERIMENT 8. By holding a clean, cold tumbler over a burning 

 taper it will be seen that water vapor is produced by the burning. 



EXPERIMENT 9. Breathing into a clean, cold tumbler shows that 

 water is produced also in the process of respiration. 



EXPERIMENT 10. A very brilliant experiment and one that is very 

 instructive at this point is to burn a watch spring in oxygen. In this 

 process the oxygen unites with the iron, forming iron oxid. 



EXPERIMENT 1 1. If a piece of watch spring be placed in water, it 

 will soon rust. Rust is also an iron oxid, only the process is slow, 

 instead of rapid as in the case of combustion, and just as much heat is 

 given off, but not much at any given instant. 



EXPERIMENT 12. If a short piece of magnesium ribbon can be 

 obtained, it may be burned in the presence of the class, though it is not 

 well to look long at the excessively strong white light. 



EXPERIMENT 13. Magnesium will also rust in water, forming a 

 white rust, or magnesium oxid, as in burning. 



EXPERIMENT 14. If a jar be filled with the slowly expired breath, 

 capped tightly, and set in a warm place it will acquire a bad odor. 



EXPERIMENT 15. Hold a thermometer at arm's length. It indi- 

 cates the temperature of the air of the air that you are breathing in. 

 Breathe for a few minutes upon the bulb of the thermometer, and the 

 fact is clearly shown that the air we breathe out is much warmer than 

 the air that we breathe in. 



EXPERIMENT 16. With a pair of bellows force the air of the room 

 through a small quantity of lime water. By continuing this process a 

 long time it may be shown that there is carbon dioxid in the air, but not 

 nearly so much as in the expired breath. 



Result of Experiments. These experiments show that 

 breathed air has gained : 



1. Heat. 



2. Water vapor. 



3. Carbon dioxid. 



4. Waste products, or impurities, having no definite 

 name, because not well known, highly putrescible, often 

 called by the general name of " organic waste matter." 



