15 



make the light. Just as soon as they are completely burned, 

 there is no more light, the same as coals cease to glow when 

 burned to ashes. 



III. Carbon dioxid. 



Let us now enquire what becomes of the carbon that we find 

 in the bright part of the flame and of the oxygen that was in the 

 air in the lamp chimney. When the candle was extinguished 

 within the chimney there was no oxygen left, as shown by the 

 lighted splinter which was put out immediately. Neither could 

 any of the particles of carbon be found except on the wick. 

 Yet they both still exist within the chimney but in an entirely 

 different condition than before. While the candle was burning 

 the little particles of carbon that we find ascending in the flame 

 are joining with the oxygen of the air and making an entirely 

 new substance. This new substance is a gas like oxygen and 

 can not be seen in the air. 



Qiies. Of what two substances is this new substance made? 



A71S. Carbon and Oxygen. 



What shall we call this substance? Since it is made of car- 

 bon and oxygen it ought, if possible, to have a name that will 

 show its composition. Its name is carbon dioxid. The words 

 carbon and oxid show of what it is made and the prefix di^ 

 which means two, shows that it contains twice as much oxygen 

 as carbon. This is represented by the formula CO2. 



Place the bit of quicklime in about half a glass of water on 

 the day previous to the experiment. W^hen ready for use there 

 will be a white sediment at the bottom and a thin white scum 

 on the top of the clear lime water. Call the attention of the 

 pupils to this white scum as a question about it will follow. 

 Make a loop in the end of the piece of wire by turning it around 

 the point of a lead pencil. Remove the scum from the lime 

 water with a piece of paper and insert the loop into the clear 

 water. When withdrawn, the loop ought to hold a film of clear 

 water. Pass the wire through a piece of cardboard or stiff" 

 paper, and arrange as shown in Fig. 18. 



Place the chimney over the lighted candle. Lower the loop 

 into the chimney and cover the top of the chimney with the 



