KEROSENE, IMPROVED TEST FOR DANGEROUS. 



465 



slowly and uniformly; 3, the temperature of 

 the oil at the beginning of the test must be at 

 least 18 Falir. below its flashing-point as ap- 

 proximately determined ; 4, the size and inten- 

 sity of the flame or spark used to produce the 

 flash must be the same in all tests ; 5, the dis- 

 tance of the flash-flame or spark from the sur- 

 face of the oil must be the same ; 6, the time 

 during which the flame or spark acts must be 

 reduced to a minimum ; T, on account of the 

 practical purpose for which the tests are made, 

 the conditions under which the vapor is formed 

 in the tester should correspond as closely as pos- 

 sible to those which determine its formation 

 and explosion in lamps, etc. It can not be af- 

 firmed that all the conditions under which ex- 

 plosions in lamps are liable to occur are pro- 

 vided for in any single testing instrument of 

 this class. The oil-reservoirs in our lamps 

 differ much in size and shape, and hence have 

 different capacities. The quantity of oil, its 

 surface, and the amount of air in the reservoir 

 with which the vapor mingles, are constantly 

 changing while the lamp is in use and the 

 danger is greatest. Moreover, it is not only 

 in quietly -burning lamps that accidents occur. 

 Probably half the accidents are due to upset- 

 ting or breaking, and the oil, which would have 

 been safe otherwise, gives rise to explosion or 

 flames under these more dangerous circum- 

 stances. It is important to employ, if possible, 

 a test which shall indicate the lowest tempera- 

 ture at which, under any conditions, inflamma- 

 ble vapors can be evolved, rather than be sat- 

 isfied with trusting to a method which merely 

 proves an oil safe under certain arbitrary con- 

 ditions. Certain testers have been proposed, 

 based upon the principle of ascertaining the 

 elastic force or tension of the vapor of the oil 

 at a given temperature : they are deceptive and 

 worthless, for it has been conclusively shown 

 that no definite relation exists between the va- 

 por-tension and the flashing-point of a kero- 

 sene. Another method of testing, by distilla- 

 tion, is exact, and has the additional advantage 

 of defining the quality of the oil as an illumi- 

 nating material. The oil is separated by the 

 distillation into three tractions : a light oil dis- 

 tilling below 150 0. ; illuminating oil, com- 

 ing over between 150 and 270 0. ; and a 

 heavy oil which boils above 270 0. The first 

 fractional distillate represents the dangerous 

 constituents, and should not exceed 5 per cent, 

 of the whole. The heavy oil affects the free- 

 dom with which kerosene burns, and should 

 not form more than 15 per cent, of the whole. 

 Victor Meyer has introduced an exact meth- 

 od of determining the minimum flashing-point 

 of kerosene by saturating the air with oil- vapor 

 at the test-temperature. His apparatus con- 

 sists of a glass cylinder which is partly filled 

 with oil, is stoppered with a cork through 

 which a thermometer passes, and is heated by 

 plunging into warm water. When the tem- 

 perature is reached at which the test is to be 

 made the cylinder is briskly shaken, the stop- 

 VOL. xxin. 30 A 



per is removed, and a small flame is intro- 

 duced. Flashing-points obtained by this plan 

 are considerably lower than those given by the 

 former methods, and are largely independent 

 of the conditions that are considered essential 

 to the accuracy of the determinations by them. 

 Haas's method is the same in principle as Mey- 

 er's, but employs an electric spark instead of a 

 flame, and the apparatus is difficult of con- 

 struction and costly. Both methods require 

 repeated shaking of the oil as the heat rises 

 from degree to degree, which is very incon- 

 venient. Liebermann has made a simple, suc- 

 cessful, dnd practical application of the same 

 principle in his tester, in which, Fig. 2, the 



FIG. 2. LIEBERMANN'B TESTER. 



saturation of air is accomplished by forcing an 

 air-current through the oil as it is warmed 

 from degree to degree ; 'and the test is made 

 by bringing a small flame to the mouth of the 

 oil-holder at the same instant. A tester of 

 still more simple construction than this has 

 been proposed. It consists, as shown in Fig. 

 3, of a glass cylinder closed at one end by a 



FIG. 3. IMPROVED TESTER. 



cork, through which a small, bent tube, d c 5, 

 passes. Just within the cork the end of this 

 tube contracts to a small orifice. The other 

 end of the tube connects with a small bellows, 

 or other source of slightly compressed air, the 

 flow of which can be regulated by the pinch- 



