IO ANSWERS TO PRACTICAL QUESTIONS 



41. Why does not a candle-wick burnt 

 There is no O at the centre of the flame. 



42. How does a chimney enable us to burn highly car- 

 boniferous substances like oil without smoke ? 



(See Chemistry, page 88.) 



It keeps out the cold air, and elevates the temperature 

 of the O, which supplies the flame. Thus more C can be 

 consumed. 



43. How much CO 2 in 200 Ibs. of chalk? 



CO, : CaCO 3 : : x : 200 Ibs. 

 44 : 100 : : x : 200 Ibs. 



100 x 8800 Ibs. 



x = 88 Ibs. (CO 2 ). 



44. What weight of CO % in a ton of marble 1 



CO 2 : CaCO 3 : : x : 2000 Ibs. 

 44 : 100 : : x : 2000 Ibs. 



zoo x 88,000 Ibs. 

 x = 880 Ibs. (CO 3 ). 



45. What is the difference between marble and chalk ? 



Marble is a compact, crystallized carbonate of lime, 

 while chalk is a porous kind of limestone. 



46. Why does not a cold saucer held over an alcohol flame 

 blacken, as it does over a candle or gas-light ? 



There is less C in alcohol than in tallow or in coal-gas. 



47. Could a light be frozen out, i. e., extinguished, by 

 merely lowering the temperature ? 



It is said to have been done in Arctic regions. 



