CARBON 



53 



Experiment 7. Place in a cylinder two grams of animal 

 charcoal, and about I cc. cochineal solution diluted with 10 cc. 

 water. Cover the cylinder with a glass plate and shake ; then 

 pour the contents of the cylinder into a filter. If the first por- 

 tion which filters, the filtrate, is not clear, pass it through the 

 filter a second time. 



Repeat the experiment, using 2 cc. potassium sulfid solution, 

 2 cc. hydrochloric acid, and 10 cc. water in place of the dilute 

 cochineal solution. 



Questions, (i) What effect did the animal charcoal have upon 

 the color of the solution ? (2) What property does this show 

 animal charcoal to possess ? (3) What was the result of filter- 

 ing the potassium sulfid solution ? (4) What property does this 

 show animal charcoal to possess ? 



56. Products of Combustion. The carbon dioxid gas 

 given off from either a candle or a gas flame can be col- 

 lected by arranging an apparatus like that shown in Fig. 

 25. A metal funnel is connected with a 

 delivery tube which passes into a solution 

 of lime water, Ca(OH) 2 , in a test-tube. 

 The carbon dioxid given off from the 

 flame passes into the lime water and by 

 forming calcium carbonate causes it to 

 become cloudy. Ca(OH) 2 + CO 2 = 

 CaCO 3 + H 2 O. The carbon comes from 

 the gas which undergoes combustion, and 

 is combined with hydrogen as hydrocar- 

 bons. That a candle produces its own 

 combustible gases can be proved by col- 

 lecting some of the gas with a glass tube Fig. 25. -collecting 



& . carbon dioxid from 



and rubber bulb as shown in Fig. 26. candle. 



This gas can then be burned as indicated in Fig. 27. The 



(X 



