28 THE PRODUCTION AND USE OF LIGHT 



32. The Inspection of Oil. If the different grades of gaso- 

 line, naphtha, and kerosene have been properly distilled and 

 purified we are able to tell fairly closely the range of boiling 

 points of the different oils, simply by testing their DENSITY, by 

 means of this hydrometer. The different states have passed 

 laws governing the manufacture and sale of the products of 

 petroleum. These laws have been passed for the protection 

 of the purchaser and user. There are oil inspectors in nearly 

 all cities and in many of the smaller towns whose duty it is 

 to inspect the products of petroleum offered for sale and to see 

 that they are really what they are said to be. In most, if not 

 all, of the states the products of petroleum must be thus inspected 

 before they are offered for sale. This test for density by means 

 of the Baume hydrometer is one of the tests. 



33. Flashing Point. The most important test, however, which 

 can be given the products of petroleum is to test their FLASH- 

 ING POINT (Art. 5, page 4). This consists in determining the 

 temperature of the oil at which the vapor arising from it will 

 flash when a flame is brought near it. It is this test which 

 determines whether an oil is safe or unsafe to have about a 

 building or to be put to certain uses. A good, legal quality of 

 kerosene is not to be considered dangerous to have in a room. 

 Any quality of gasoline, on the other hand, is always to be 

 considered dangerous, and must be cared for accordingly. A 

 very simple experiment will show us that this is so, and will 

 help us to understand why it is so. 



Exercise 18. Flashing Point of Gasoline and Kerosene 



Put four or five tablespoonfuls of kerosene in a tin cup. Place the 

 bulb of the thermometer in the oil and take its temperature. Record 

 this. Light a match and try to set the kerosene on fire. Are you 

 successful? Try again. Make a sufficient number of trials to sat- 

 isfy yourself whether or not you are able to set the kerosene on fire. 

 It is not probable that you will succeed, but if you should finally get 

 it to burn, smother the flames quickly by placing a piece of glass over 

 the dish so as to exclude all air. .Take the temperature of the oil 

 again and record all that happened. 



