PETROLEUM AND ITS PRODUCTS 23 



it gives off a strong odor which is disagreeable to most people. 

 In the region of oil wells the whole atmosphere is charged 

 with this odor for miles around. This simply means that 

 as the petroleum comes from the well some of it immedi- 

 ately evaporates, or passes off into the air in the form of vapor, 



Or gas, NATURAL GAS. 



We are not greatly surprised to find that this is so, for we 

 have seen that water left uncovered is constantly evaporating. 

 We have also seen that alcohol left uncovered evaporates even 

 more rapidly. It is the same with all other liquids, though 

 some evaporate very rapidly and others very slowly. 



We have also seen that heating water or alcohol, or a mix- 

 ture of the two, increases the rate of evaporation. If we heat 

 either liquid hot enough, it boils and vaporizes with great 

 rapidity. 



26. The Distillation of Petroleum. Remove the stopper 

 from the bottle of petroleum. Notice carefully the color and 

 odor. If we were to place a little in a vessel and heat it, we 

 should see that it boils quickly. Hence, petroleum would seem 

 to behave very much as water or alcohol does so far as evapora- 

 tion and boiling are concerned. To understand the real na- 

 ture of petroleum, however, it will be necessary to keep con- 

 stantly in mind all the facts we observed when we distilled the 

 mixture of alcohol and water. What did we notice in regard 

 to the boiling point of the mixture? Did it remain constant? 

 At what temperature did it begin to boil? What was its boil- 

 ing point when we stopped the experiment? What was our 

 conclusion? We must keep these things in mind while we 

 perform the following experiment: 



Exercise 17. To Distil Petroleum 



Fill a 4-oz. distilling flask half full of petroleum, using a funnel so 

 that no petroleum enters the delivery tube. Put some small nails or 

 beads into the flask. Clamp the flask to the stand as in Ex. 15 and 

 insert the stopper and the thermometer, which must have a scale 

 which reads to about 360C. or 680F. The lower end of the bulb 

 of the thermometer should reach about % in. below the side tube. 



