20 THE NATURE AND NEEDS OF LIVING MATTER 



Method. Put some nails or tacks in the bottle and cover them with 

 the weak sulphuric acid. Insert cork and delivery tube as in Figure 4. 

 Permit the gas to escape for a short time, wrap 

 the bottle in a cloth, and try igniting the escap- 

 ing gas. 



Note. The iron pushes off a gas (hydrogen), 

 w which was a part of the acid. It appears as 

 bubbles and passes out of the glass tube. 



Conclusions. 1. Does hydrogen burn (oxi- 

 dize) ? What is the result ? 



2. What collects on a tin cup half filled with 

 water held at the top of the flame ? 



3. With what does hydrogen unite when it 

 burns ? 



4. What is the result of this union ? 



d. Carbon (C) and Carbon 



Dioxide (C0 2 ) 



Apparatus. Piece of wood charcoal, 

 soft coal, clay pipe, shavings, clay, alco- 



FIG. 4. -Making hydro- ho1 lam P Or BuDSen burner, wide-mouth 

 gen. 10, cup half bottle, limewater, sugar or starch, test 

 filled with water, as tubes. 



a condensing agent. Method a. Put some bits of wood in 



the clay pipe and closely cover them with the clay which has 

 been wetted to form a pasty cover, and heat the pipe very hot 

 for a few minutes. Try to light any gas that may issue from 

 the stem of the pipe. 



Observations. 1. What is the color of carbon in charcoal ? 

 Is the carbon in the pipe like that in the charcoal stick ? 



2. How does the carbon separated out in the pipe compare 

 with that in the charcoal stick ? 



3. What happened when a lighted match was held where 

 the gases were escaping ? 



Note. Gas for lighting houses was formerly made in a 

 similar way by heating soft coal in iron boxes. 



Conclusions. 1. What is one of the elements in wood ? 

 2- How does carbon differ from oxygen ? 



