CHAPTER VII CARBON AND CARBON DIOXIDE 50. Carbon. a. Arrange an apparatus as shown in Fig. 28. Partly fill the hard-glass test tube A with small pieces of wood-preferably with hardwood sawdust. Heat the wood, gently at first and then more strongly. After some liquid has collected in B, apply a light to the jet C. Are combustible gases evolved on distilling wood? Continue the heating as long as gas is evolved, then examine the liquid collecting in B. Is it soluble in water? How would you describe its odor? What is the residue left in A? Will it burn? Does it leave any ash? b. Bring a cold porcelain dish into a small, luminous Bunsen flame. Note the de FIG. 28 B posit. What is this form of carbon called? In what other forms does carbon exist? What properties have all these forms in common? c. Put one fourth of a test tube full of bone black into a small flask and pour over it about 50 cc. of water, to which has been added a few drops of a solution of litmus or of indigo. Thoroughly mix the contents of the flask, then heat it gently for a few minutes, and filter. If the filtrate is not CHAPTER VII CARBON AND CARBON DIOXIDE 50. Carbon. a. Arrange an apparatus as shown in Fig. 28. Partly fill the hard-glass test tube A with small pieces of wood-preferably with hardwood sawdust. Heat the wood, gently at first and then more strongly. After some liquid has collected in B, apply a light to the jet C. Are combustible gases evolved on distilling wood? Continue the heating as long as gas is evolved, then examine the liquid collecting in B. Is it soluble in water? How would you describe its odor? What is the residue left in A? Will it burn? Does it leave any ash? b. Bring a cold porcelain dish into a small, luminous Bunsen flame. Note the de FIG. 28 B posit. What is this form of carbon called? In what other forms does carbon exist? What properties have all these forms in common? c. Put one fourth of a test tube full of bone black into a small flask and pour over it about 50 cc. of water, to which has been added a few drops of a solution of litmus or of indigo. Thoroughly mix the contents of the flask, then heat it gently for a few minutes, and filter. If the filtrate is not decolorized, repeat, using more bone black. What is the composition of bone black? By what other name is it known? What use does this experiment suggest for it? d. Is carbon at ordinary temperatures an active element? Test it with the common acids. How does the charring of wood preserve it? e. Prepare an apparatus according to Fig. 29. The bottle A contains a solution of sodium hydroxide, while B and C contain a solution of calcium hydroxide (limewater). The hardglass tube D contains one or two small pieces of charcoal. Charge your oxygen generator as in § 15 and connect the rubber delivery tube with E. Now pass a slow current of oxygen through the apparatus, at the same time heating the charcoal in D until it just begins to glow. Describe the results. What do they prove? Why pass the oxygen through the solutions in A and B? What reactions take place in D and C (R)? E D FIG. 29 f. In a hard-glass test tube heat an intimate mixture of 2 or 3 g. of black copper oxide and an equal bulk of powdered charcoal. Pass the evolved gases through a little limewater in a test tube. Write all the equations involved in the reactions. What remains in the test tube? How can you prove it? What use does this suggest for charcoal? 51. Carbon dioxide. a. Put some pieces of marble in your hydrogen generator, cover them with water, and add a little concentrated hydrochloric acid through the funnel tube. Fill two or three bottles with the gas evolved by downward displacement. (To test whether the bottles are filled or not, hold a burning splint in the mouth of the bottle.) b. Devise an experiment to show whether the gas is heavier or lighter than air. Attempt to pour it from one bottle to another, as you would a liquid, and test with a burning splint for its presence in the second bottle. |