There are two kinds of tests: the " flash test," which determines the low est temperature at which oil gives off an inflammable vapor, and the " burn ing test," which determines the lowest temperature at which the oil takes fire. This test is made commercially by means of an apparatus having a cup to hold the oil, in which the bulb of a thermometer is immersed, and which is surrounded by a vessel of water heated by an alcohol lamp. The temperature is slowly increased at the rate of about 2 per cent a minute. The oil is stirred at inter vals, a flame applied, and the point noted at which an inflammable vapor is given off, and also at which the oil takes fire.
A rough test for ordinary purposes may be made by filling a cup with water, inserting an ordinary ther mometer, and bringing the tempera ture to 110° over a slow fire. Pour a tablespoonful of oil on the water, and apply a lighted match. If the oil takes fire it is unsafe and is liable to explode. Dealers who sell oil that will not stand this test at 110° are liable to prosecution by law. They should be compelled to take back the oil and refund the price paid for it.
To Purify Kerosene.—The adultera tion of oil by means of a heavier oil than standard kerosene causes a dim ness of the flame and charring of the wick. The best kerosene oil is clear and nearly colorless, like water. To puri fy kerosene oil, add to 100 pounds of oil 1 pound of chloride of lime, mixed with 12 pounds of water to the con sistency of cream. This must be done in a lead-lined vat, as iron or copper will be corroded by the process. Thor oughly mix these materials, let stand over night, and add 1 or 9 pounds of sulphuric acid diluted with 90 to 50 parts of water and boil with gentle heat, stirring constantly until a sam ple tested on a glass plate is perfectly clear. Let the mixture settle, when the oil will rise to the top and can be drawn off, leaving the impurities in the form of sediment mixed with the acidulated water.
The following four paragraphs are adapted from Macbeth's " Index." The Care of Lamps.—Lamps smell and give poor light: first, because they are not kept clean; or secondly, the wick is poor or clogged by having been used too long; or thirdly, the chimney is wrong.
Trim, clean, and fill daily, and wipe the whole lamp.
Trim by rubbing the char off the wick; this leaves it even. Don't cut it; you can't cut it even.
Keep the holes in the floor of the burner clear for draught.
Don't fill quite full; the oil expands with heat and runs over.
Boil the burner a few minutes once a month in sal soda or lye water.
Empty the fount occasionally for sediment.
Don't open the lamp when hot; there is explosive vapor in it.
Light it with the wick turned low and turn up gradually, or you will get it too high and make smoke.
Move with care a lamp that has been burning long enough to get hot; or, better still, don't move it.
Use the American Fletcher or Hyatt wick; and renew it every month or two, no matter how fresh it looks; it gets clogged and doesn't feed freely.
Use oil of not less than 110° flash for safety; the higher the flash the safer the oil.
Lamp Chimneys. — The object of lamp chimneys is to supply the flame with exactly the amount of air it needs for perfect combustion, no more and no less, with an even draught on both sides of the flame; they must, of course, be deal: and transparent. This calls for fit in the full meaning of the word and for clear glass that will stay, clear. Thus there is something to know about chimneys beyond the mere size of the bottom. The ordinary notion of fit is a chimney that will stay on the lamp and not fall off. That is part of the fit. The rest is such a shape as to make the right draught for that particular lamp. It includes the seat, bulb, shaft, propor tion, sizes in all parts, and length. Good chimneys that fit well give more light than common ones. This is due to perfection of shape and proportion and the right balance of draughts.
To Select Chimneys.—Use the chim ney recommended by the maker of the lamp, or write to a manufacturer of lamp chimneys for his catalogue and order according to directions.
If compelled to buy from stock, try one chimney after another, turning up the wick in each case till you get the most light it will give. When you have the right one, you can turn the wick higher and get more light than you can from others, in some cases perhaps twice as much. It pays to select chimneys with care for two rea sons: one is, the right chimney gives more light; the other is, it lasts longer. Chimneys are usually made in three grades, of which it always pays to buy the best. Comparing bad chimneys with good ones, the breakage is ten to one, the light is half, and the price is half.