6 PLANT BIOLOGY 



allow it to stand until needed. Then pour some of the liquid through 

 a funnel in which is a filter paper. Collect the filtered lime water 

 in a bottle, and keep it stoppered. As soon as it becomes cloudy, 

 throw it away and obtain some more clear liquid by filtration as di- 

 rected above. The large bottle can be kept indefinitely as a stock 

 solution if it is kept filled with water.. 



9. Carbon (symbol, C). Laboratory Study No. 1. Sug- 

 gested as home work. 



1. Prepare some charcoal by lighting a long splinter of wood 



or a match and then blowing out the flame. (Pre- 

 pared charcoal may be used.) Charcoal is nearly 

 pure carbon. 



a. Tell what you have done. 



b. Is carbon (charcoal) a solid, a liquid, or a gas ? What 



is its color ? 



c. Of what substance does this experiment prove that 



wood is partly composed ? 



2. Hold the tip of the carbon (charcoal) in a hot flame. 



a. State what was done. 



b. Does any of the carbon disappear? 



c. Will carbon burn ? How do you know ? 



3. State three characteristics of carbon (charcoal) that you 



have learned from these experiments. 



4. Hold your hand over the glowing charcoal with your eyes 



closed. How can you still tell that the carbon is 

 burning ? 



10. Oxygen (symbol, O). - Laboratory Study No. 2. 

 Demonstration. 



Preparation of oxygen: Thoroughly mix a teaspoonful of po- 

 tassium chlorate with about one-fourth as much black oxid of man- 

 ganese. Put the mixture in a large test tube. Close the mouth of 

 the test tube with a stopper through which passes a delivery tube, 

 the other end of which runs beneath the surface of water in a tray. 

 Support the test tube in a slanting position on an apparatus stand, 

 and heat the mixture gently with a gas or an alcohol flame, until 



