22 THE PRODUCTION AND USE OF LIGHT 



* T.yZero F. is what temperature on the centigrade scale? 



Ans. -17%C. 



8. Prove that if mercury freezes at 40C. that it also freezes 

 at -40F. 



9. 10F. is what temperature on the centigrade scale? 



10. The temperature of the human body is 98.4F. What is it on 

 the centigrade scale? 



11. The temperature of a living room should be about 70 F. 

 What should it be on the centigrade scale? 



12. What is the boiling point of mercury on the Fahrenheit scale? 



13. What is the boiling point of oxygen on the Fahrenheit scale? 

 Of hydrogen? 



14. Gold melts at 1080C. What is this temperature on the Fahren- 

 heit scale? 



15. If the lowest temperature reached in the winter is 25F. 

 and the highest temperature of the summer is 100F., what is the 

 total range of temperature (1) in Fahrenheit degrees, (2) in centi- 

 grade degrees? 



16. Common salt melts at 1320F. and aluminum melts at 

 625C. Which is the higher melting point? Could salt be melted 

 in an aluminum dish? 



17. Under the pressure of 15 Ib. per sq. in. water boils at 213F.; 

 under the pressure of 30 Ib. it boils at 250F.; under the pressure of 

 100 Ib. it boils at 328F.; under the pressure of 200 Ib. it boils at 

 382F. What is each of these temperatures on the centigrade scale? 



18. The electric furnace produces the highest artificial tempera- 

 ture known. It is usually estimated at about 4000C. Ball esti- 

 mates the temperature of the sun to be about 14,000F. Compare 

 these two temperatures. 



19. Solder is made of a mixture of tin and lead. Lead melts at 

 326 C. and tin melts at 230C. A certain sample of solder melted 

 at 390F. Compare these -temperatures and state the peculiar fact 

 you notice. 



20. A person with a fever has a temperature of 105. A steam 

 radiator has a temperature of 110. Many people cook eggs at a 

 temperature of 180. The temperature of the schoolroom should be 

 kept at about 70. On a certain day a rain-storm suddenly turned 

 into a snow-storm ; the thermometer then indicated a temperature of 

 5. Which scale is referred to in each of these cases? 



IV. PETROLEUM AND ITS PRODUCTS 

 25. Petroleum. When petroleum first comes from the 

 well it is usually of a dirty, dark, bluish-brown color; usually 



