44 CIIEMISTR V FOR A GRICUL TURAL S TU DENTS 



4. Express 30 inches in millimeters. 



5. What is the weight of 10 liters of pure water at 4° C. ? 

 *6. Calibrate the burette. 



The Atmosphere. 



7. Describe how the weight of a liter of air can be ascertained. 



8. To what is the atmospheric pressure due, and how may it be proved 



that the height of the mercury in a barometric tube depends upon 

 the atmospheric pressure ? 



9. Mercury is 13I times as heavy as water. Calculate the pressure of 



the atmosphere upon the surface of the earth at sea level in grams 

 per square centimeter, and in lbs. per square inch. 



10. Mercury is 11,000 times as heavy as air at sea level ; what would be 



the height of the atmosphere in miles, were the density the same 

 throughout ? 



11. The action of a suction pump in drawing water depends upon the 



atmospheric pressure. Calculate the height to which it would be 

 theoretically possible to draw water, were the water absolutely 

 pure and the valves of the pump air-tight. 

 *I2, The daily barometric readings for March 1898 were — 30.5, 30.6, 30.4, 

 30.3, 30.0, 30.4, 29.9, 29.6, 28.8, 29.7, 29.2, 29.7, 30.0, 30.0, 

 30.0, 29.8, 29.8, 29.1, 29.1, 29.3, 28.8, 29.5, 29.5, 29.3, 29.3, 

 29.6, 29.9, 30.1, 30.2, 30.2, 30.3. Express these variations 

 graphically on the square paper. 



Composition of Air. 



13. Name the active and the inactive constituents of the air, and state in 



what proportion they are present. 



14. When iron rusts under a bell jar standing over water, what changes 



take place in (i) the weight and properties of the iron, and (2) the 

 volume and properties of the air ? 



15. When phosphorus burns, what happens to the phosphorus and to the 



air ? In what respects is the combustion of phosphorus similar to 

 the rusting of iron ? 



16. What is an oxide? How may the oxides of iron and phosphorus be 



formed ? 



17. What is a chemical compound, and how would a chemical compound 



of two elements be distinguished from a mixture? Illustrate youf 

 answer by the compounds of oxygen with iron and phosphorus. 

 *l8. Prepare a bottle full of nitrogen gas. 



