IN POPULAR CHEMISTRY. 79 



but the light diminished. The principle is that of Bunsen's 

 burner. 



23. Why does not the lime burn in a calcium-light ? 



Lime is a burned body ; its symbol is CaO. 



24. Why is a candle-flame tapering ? 



(See Chemistry, p. 77.) 



The currents of air rushing toward the flame from all sides 

 give it the conical form. 



25. Why does a draught of air cause a light to smoke ? 



It lowers the heat of the flame below the point of union 

 between C and O, and thus the C is precipitated. 



26. Wliat makes the coal at the end of a candle-wick ? 



The wick at the edge of the flame comes in contact with 

 the O of the air, and therefore burns. 



27. Which is the hottest part of a flame ? 



Toward the point of the cone, where the gaseous envelopes 

 meet and make a solid flame. 



28. Why does not a candle-wick burn eoccept at the 

 edge of the flame ? 



There is 110 O at the center of the flame. 



29. How does a chimney enable us to burn without 

 smoke highly carboniferous substances like oil ? 



It prevents the heated products of combustion from becom- 

 ing mixed with cold air. These rise, and new air can come in 

 only at the bottom. The stronger the heat in the chimney the 

 greater is this draught. A flame, in which the combustion is 

 imperfect when O is supplied slowly, becomes much brighter 

 when O is supplied fast enough to produce perfect combustion 

 of the H, and also to oxidize all the C without allowing any to 

 pass off as smoke. 



30. How much CO a in 20O Ibs. of chalk ? 



