Fire and Heat 83 



Slow oxidation of many oils and of some other substances may 

 result in spontaneous combustion. 



Oxids are products of the union of oxygen and other substances. 



Oxygen is indispensable to life, is useful in medicine and industry, 

 and is the most abundant element. 



REVIEW QUESTIONS 



1. How did Lavoisier prove that a combustible substance burned 

 in air gains in weight? 2. What does lead burned in a closed dish 

 show? 3. What proportion of air seems to be used in such burning? 

 4. Describe how it may be shown that a certain part of the air is 

 necessarily concerned in combustion. 



5. What do you find to be the properties of nitrogen as to solu- 

 bility in water? support of combustion? support of life ? weight? 

 activity? 6. Why was nitrogen called " vitiated air "? What is its 

 proportion in the air? 7. What is the use of nitrogen in the air? 



8. What part of the air unites actively with burning substances? 

 9. What are the characteristics of oxygen as to visibility? taste? 

 odor? solubility? support of combustion? support of life? 10. 

 What is oxidation? Give instances of different rates of oxidation 

 of substances. 11. Describe a method for the production of oxygen 

 on a large scale. 12. What are the physical properties of a sub- 

 stance? 13. What are oxids? Why are they so named? 14. What 

 is the meaning of the term " dioxygen " or dioxid? 15. What use is 

 made of oxygen in life processes? in medicine? in manufacture? 



16. Why does the chemist consider oxygen as especially active? 



17. What is the relative abundance of oxygen? 



SUGGESTIVE QUESTIONS 



1. Why is metallic lead not found in nature? 2. If air is indis- 

 pensable to combustion, why does the fire in a stove or furnace keep 

 overnight when all drafts are closed? 3. Fires in holds of ships are 

 sometimes extinguished by blowing in steam from the boilers. Ex- 

 plain. 4. Describe some experiment not in the text to show that air 

 is necessary to burning. 5. Why would prolonged inhalation of oxy- 

 gen not be altogether beneficial? 6. What does it mean to say that 

 gold does not "rust"? 7. Explain "spontaneous combustion," 

 and if possible give instances. 8. Suppose the proportion of oxygen 

 in the air were decreased by one half ; what changes do you imagine 

 would have to occur to make human life possible? 



