THE CHEMISTRY OF THE ATMOSPHERE. 109 



are varied under certain restricting circumstances. For ex- 

 ample, the air in a close room where there are many per- 

 sons has its oxygen lessened, and its carbonic anhydride in- 

 creased, and still it is air a mixture, but with the propor- 

 tions of its ingredients altered. So, also, when air is dis- 

 solved in water, the proportions of its ingredients are not 

 the same as before it was dissolved ( 134). Then, again, the 

 qualities of air are not wholly different from its constituents, 

 as is the case with compounds ( 85), but they are midway be- 

 tween those of oxygen and nitrogen. And, lastly, if we min- 

 gle these two gases in the same proportions that occur in air, 

 the mixture has nearly all the properties of the atmosphere. 



QUESTIONS'. 



115. What are the ingredients of the atmosphere, and in what propor- 

 tions ? 116. How large is the total amount of carbonic anhydride in the 

 air? 117. What is the chief use of nitrogen in the air? What would 

 happen if all the air were oxygen ? 118. Explain the two methods of ana- 

 lyzing the air. How is the moisture removed in the second operation ? 

 119. What is said of the influence of gravitation on gases? What would 

 result if there were nothing tending to counteract this ? 120. Describe 

 an experiment illustrating diffusion. 121. State fully the analogy between 

 liquids and gases in regard to mingling. 122. What is said of the Grotto 

 del Cane ? 123. What of the accumulation of carbonic anhydride in wells? 

 How can it be removed ? 124. What two gases are produced by the burning 

 of charcoal ? Which is the most destructive ? What is to be done when 

 persons are suffering from the fumes of charcoal? 125. How can you show 

 that carbonic anhydride is discharged from the lungs ? What is a precipi- 

 tate? Explain the experiments to illustrate this exhalation. 126. Why 

 is the bad influence of poor ventilation not commonly appreciated? Are 

 the bad effects of imperfect ventilation due to the carbonic anhydride sole- 

 ly? 127. What are the sources of carbonic anhydride in the air ? 128. De- 

 scribe the chemistry of the leaves. 129. What influence has the sun upon 

 the chemistry of leaves ? 130. State Priestley's experiment. 131. State in 

 full what is said of the wonderful balancing power of the chemistry of the 

 atmosphere. 132. How is nitrogen in contrast with the other ingredients 



