An oil that will stand 100 flash will stand 110 burning test every time. Kerosene oil, at ordinary temperature, should extinguish a match as readily as water. When heated it should not evolve an inflammable vapor below 110 degrees, or, better, 120 degrees Fahrenheit, and should not take fire below 125 to 140 degrees Fahrenheit. As the temperature in a burning lamp rarely exceeds 100 degrees Fahrenheit, such an oil would be safe. It would produce no vapors to mix with the air in the lamp and make an explosive mixture; and, if the lamp should be overturned, or broken, the oil would not be liable to take fire. The crude naphtha sells at from three to five cents per gallon, while the refined petroleum or kerosene sells at from fifteen to twenty cents. As great competition exists among the refiners, there is a strong inducement to turn the heavier portions of the naphtha into the kerosene tank, so as to get for it the price of kerosene. In this way the inflammable naphtha or benzine is sometimes mixed with the kerosene, rendering the whole highly dangerous. Dr. D. B. White, President of the Board of Health of New Orleans, found that experimenting on oil which flashed at 113 degrees Fahrenheit, an addition of one per cent. of naphtha caused it to flash at 103 degrees; two per cent. brought the flashing point down to 92 degrees, five per cent. to 83 degrees, ten per cent. to 59 degrees, and twenty per cent. of naphtha added brought the flashing point down to 40 degrees Fahrenheit. After the addition of twenty per cent. of naphtha the oil burned at 50 degrees Fahrenheit. There are two distinct tests for oil, the flashing test and the burning test. The flashing test determines the flashing point of the oil, or the lowest temperature at which it gives off an inflammable vapor. This is the most important test, as it is the inflammable vapor, evolved at atmospheric temperatures, that causes most accidents. Moreover, an oil which has a high flashing test is sure to have a high burning test, while the reverse is not true. The burning test fixes the burning point of the oil, or the lowest temperature at which it takes fire. The burning point of an oil is from ten to fifty degrees Fahrenheit higher than the flashing point. The two points are quite independent of each other; the flashing point depends upon the amount of the most volatile constituents present, such as naphtha, etc., while the burning point depends upon the general character of the whole oil. One per cent. of naphtha will lower the flashing point of an oil ten degrees without materially affecting the burning test. The burning test does not determine the real safety of the oil, that is, the absence of naphtha. The flashing test should, therefore, be the only test, and the higher the flashing point the safer the oil.