HEAT IN RELATION TO THE HUMAN BODY 11 



Explain the persistence (a) of the inner cone ; (6) of the 

 wick. 



6. Put the tip of a blowpipe into the inner cone of the 

 candle flame, and by repeated trials cause the yellow part 

 of the flame to very nearly disappear. What is the explana- 

 tion of this change ? 



Hold the inner edge of an evaporating dish in this blow- 

 pipe flame for a moment. Then hold another part of its 

 surface in the candle flarne. Observe any deposit on the 

 dish in either case, and state its probable nature and source. 

 Account for any variation in amount of the deposit in the 

 two cases. Give an explanation of the light-giving power of 

 the yellow part of the candle flame. 



7. Hold a clean dry bottle mouth down over a burning 

 candle, and look for any moisture (water) on the sides of 

 the bottle. Assuming that there is no water in the candle 

 material, account for its appearance in the bottle. 



Observe a lighted splinter when it is put" down into the 

 bottle that has just been held over the candle flame, and 

 explain the results. Set the bottle aside with a cover on it. 

 When it is cold put into it a little limewater (10 c.c.) and 

 shake. Any milky appearance of the limewater is due to 

 the presence in the bottle of the gas carbon dioxide. 



8. Breathe through a glass tube into limewater in a test 

 tube till a marked change occurs in the appearance of the 

 limewater. What is the significance of this change ? What 

 is indicated concerning processes within the body ? Whence 

 is derived (a) the oxygen ; (6) the carbon ? In what re- 

 spects does this oxidation within the body differ from or- 

 dinary combustion? What significance has the fact that 



