HYDROCARBONS 7 



EXPERIMENT STUDY I 



Hydrocarbons from Wood and Coal 



(i) {a) Place a few dr>' wood shavings in a hard glass test 

 tube. Fit the test tube with cork, glass and rubber tubing connec- 

 tions with a glass jet at the end. Heat the tube slowly and notice 

 the moisture given off before the wood begins to char in case the 

 wood was not perfectly dry. As the temperature becomes high 

 enough to char the wood, notice the collection of moisture on the cool 

 parts of the tube. This moisture comes from the decomposed wood. 

 What two elements are, therefore, present in the wood ? (b) When 

 gas is being generated fast enough ignite it at the jet. Note char- 

 acter of flame, (c) Hold the burning jet inside a cool, dry, empty 

 bottle. Let the jet burn in the bottle as long as possible. What 

 does the moisture here prove? After the flame ceases to burn in 

 the bottle pour into the bottle 25 c.c. limewater, and shake. The 

 white precipitate proves that carbon dioxide (CO2) is present. What 

 does this mean? (d) Hold the burning jet against a cold piece of 

 porcelain. What does this show? What do all these tests prove 

 as to the elements contained in wood ? 



(2) Repeat (i), using powdered soft coal instead of wood. 

 The gas produced here is crude illuminating coal gas. 



(3) Mix in a mortar i gram of wheat flour and an equal volume 

 of fine soda lime. Heat the mixture in a test tube, and hold a piece 

 of moist, red litmus paper at the mouth of the tube. Smell the gas 

 given off. What is it ? What element does this prove to be present 

 in the flour? 



MARSH GAS — METHANE 



Occurrence. — The gas rising from stagnant pools of water 

 which contain decaying organic substances, commonly known 

 as marsh gas, is known chemically as methane. It has also been 

 obtained from petroleum and from coal and is found naturally 

 in pockets and crevices in coal strata. It is prepared in the 

 laboratory from a salt of acetic acid, a related compound, but 

 it will not be necessary at this time to give the reactions in- 

 volved in the preparation. (See Exp. II, i, a) 



