24 THE PRODUCTION AND USE OF LIGHT 



As the experiment proceeds the thermometer may have to be raised 

 or lowered in the stopper in order that its reading may be taken. 

 Place the piece of cardboard between the distilling flask and the ves- 

 sel into which the distillate will drip. Guard against possible accident, 

 such as the cracking of the flask. While it is extremely improbable 

 that the flask will crack, it is well to set the entire apparatus in an 

 ordinary dripping pan or some flat-bottomed vessel and to keep a wet 

 towel near with which to smother the flames in case of accident 

 (See Fig. 12). 



Place the lamp under the flask and gently heat the petroleum. 

 Notice that it begins to boil very soon. As soon as you see the vapor 

 pass over into the delivery tube and there condense, read the ther- 

 mometer. Catch the distillate in a small, clean bottle. Notice the 

 color and appearance of the distillate. Watch the thermometer 

 carefully. Is the tempera turq. rising steadily? When it reaches 

 70C., or 158F., remove the bottle in which you have been catching 

 the distillate and place another in position. Label this first bottle 

 "Distillate No. 1." Does the temperature still continue to rise? 

 When it reaches 80C., or 176F., again remove the bottle in which 

 you have been catching the distillate and label it " Distillate No. 2." 

 In the next bottle catch the distillate till the temperature has risen 

 to 120C., or 248F. Label this " Distillate No. 3." Catch in a 

 fourth bottle the distillate which passes over between 120C. and 

 150C. and label it " Distillate No. 4." Finally in a fifth bottle catch 

 the distillate which passes over between 150C. and 300C. It will be 

 found necessary to heat more strongly now and possibly to enclose 

 the flask partly in a shield of tin or asbestos paper in order to raise 

 the temperature to 300C. This last portion of the distillate will 

 probably contain about one-half of the entire distillate. Remove the 

 lamp and pour as much of the residue as possible out of the flask while 

 it is still hot. When it cools it will be solid and cannot be removed 

 readily from the flask. Wash the flask out clean with gasoline so 

 that it will be ready for future use. 



Caution. Gasoline should be used for this purpose out of doors, or, 

 if in the house, the doors and windows should be left open so that the wind 

 may quickly remove the vapor from the room. Never use gasoline when 

 there is a flame near. 



27. The Products of Petroleum. In this last experiment we 

 have separated the crude petroleum into six different portions. 

 The process is FEACTIONAL DISTILLATION, and the products are 

 practically the products of petroleum as they are sold on the 



