INTRODUCTORY EXERCISES 15 



gas. This gas is the only one that will cause the change in 

 limewater noted above.) 



Rinse out the bottle with water. Light the wood splinter 

 and thrust into the bottle. Proceed as with the charcoal. 

 Test the contents of the bottle with a drop of lime- 

 water. What evidence have you that wood contains 

 carbon? 



Burn the piece of meat by heating it in the test tube. 

 Suspend a drop of limewater in the tube by means of the 

 glass tube. What evidence have you that animal flesh 

 contains carbon? 



Place the piece of marble in a clean test tube. Pour on it 

 a little hydrochloric acid which has been diluted previously 

 with twice its volume of water. What evidence of action* 

 have you? Hold suspended a drop of limewater in the mouth 

 of the tube. Hydrochloric acid and water contain no car- 

 bon ; what must you conclude as to the presence of carbon 

 in the marble? 



(Carbon is to be found in all animal and vegetable com- 

 pounds and in some minerals.) 



Pour some of the limewater into the beaker. By means 

 of the glass tube blow some of your breath through the 

 liquid in the beaker. In what form is the carbon in your 

 breath? (Expired air contains about 4 parts of this gas in 

 every 100 parts of the expired air. Ordinary air contains 

 about .04 part of this gas in 100 parts, or about 4 parts in 

 every 10,000 parts of air.) 



(Besides charcoal, the other forms of carbon are diamond 

 and graphite. All the forms of carbon are odorless, taste- 

 less, and insoluble in water; and if strongly heated in the 

 presence of oxygen, each form of carbon will combine with 

 it and form carbonic acid gas.) 



