September i, 1893.] 



SCIENCE. 



"5 



SCIENCE: 



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CUEEENT NOTES ON CHEMISTRY.— II. 



lEdited by Charles Piatt, Ph. D., F. G. S.] 

 Flash Point of Mineral Oils. 



While not strictly chemical in its nature there are but 

 few scientific tests so intimately connected with our safety 

 as the determination of the flash and burning points of 

 mineral oils. This has long been a matter of concern to 

 oil merchants alone, but the scientific public is no w tak- 

 ing an interest in the matter, which it is hoped will de- 

 crease, if not do away with altogether, the vast number of 

 preventable lamp explosions and fatalities. 



The safety of an oil is determined by its flash point, that 

 temj)erature at which an explosion occurs when a flame is 

 applied to the mixture of air and vapor immediately above 

 the surface of the oil. A flash occurs, but the oil does not 

 take fire and burn continuously, in the ordinary test cu2>, 

 until a higher temperature is reached, its bui'miiy or firing 

 point. Originally the test was applied to the oil in an 

 open cup, but, this method introducing many chances of 

 error, a closed cup was finally adojDted, the flame being 

 inserted through a hole in the cover. 100° F., formerly 

 considered as the minimum safety point for oil, in the 

 open cup corresponds to 73° P. in the closed test, and 

 with the adojjtion of the latter, the British Government, 

 advised by Sir Frederick Abel, lowered the minimum 

 safety point required by law to this temperature ! The 

 reports and papers by Sir Frederick Abel and by Mr. 

 Redwood, who was associated with him, contain many out- 

 rageous assertions, among others that an oil flashing at 

 a low temperature is more safe than one flashing at a high 

 temperature. They argued that by using the low-test 

 oils a greater volume of vapor is given off and the air is 

 thus driven from the lamp. A metal lamp was also 

 recommended as the safest on this same principle, that by 

 the heating of the oil in the lamp reservoir vapors are 

 evolved from the oil, and the air being driven out as be- 

 fore, an inflammable, bLit not an explosive, mixture is ob- 

 tained. When we consider that 73° F., adopted by the 

 British Government, is a temperature freqiiently exceeded 

 in our houses, the danger of such a ruling is apparent. 

 Mr. D. E. SteLiart presented an admirable paper to the 

 Glasgow and Scottish Section of the Society of Chemical 

 Industry, early last winter, in which the fallacies of 

 Abel's position were forcibly shown. His paper was thor- 

 oughly discussed by the members at that meeting and 

 subsequently, with the final result of an appointment of a 

 committee of experts to pass upon the question. Their 



report fully sustained Mr. Steuart and recommended a 

 higher flash point of minimum safety than that now es- 

 tablished by law. Mr. Steuart's paper, presented at that 

 time, and others of more recent date, contain many inter- 

 esting facts relative to the burning of oils, as, for in- 

 stance, the relation between flash point and heat devel- 

 oped in burning, the effect of the presence of heavy oils, 

 of chemicals, etc., and of the size of the container. 



A lamp burning badly develops more heat than usual, 

 the light is red and the combustion imperfect, producing 

 a disagreeable odor. This may arise from the air not be- 

 ing properly reverberated against the flame; or from the 

 shajie of the chimney allowing of back currents; or from 

 the lamp being dirty, the air holes clogged, the wick 

 damp or dirty; the presence of a trace of vegetable or 

 animal oil in the vessels used for filling; or from the oil 

 itself, the presence of heavy oils or refining chemicals. 

 When the oils are not homogeneous, a light and heavy 

 oil being mixed, the heat developed is greater than with 

 either oil separately, this result being more pronounced 

 when a poor wick is used. A well fractionated oil is 

 practically independent of the wick. The treatment of 

 the oil after the last distillation with acid and alkali, re- 

 sults in injury to it, no matter how thorough the final 

 washing. Sulpho compounds of soda are often retained, 

 and these decompose in the burner, forming sulphuric 

 acid, which chars the wick. Carefully fractionated oils 

 are low or high, in flash, in proportion to the specific 

 gravity and boiling point. A low-flashing oil gives the 

 highest temperature in burning. (Contrary to Abel and 

 Eedwood). 



Another feature has been brought to our attention 

 lately, that of the influence of the size of the containing 

 vessel upon the danger point in oils. The Abel test, it 

 will be remembered, is prescribed as a two-inch cup. A 

 particLilar sample flashed in Abel test at 78° F. ; in 

 the old government open test at 105° F., and fired in 

 the old government open test at 122° F. Although a 

 small cup of this oil cannot supply vapor sufficient for a 

 constant flame below 122° F., a larger surface can. 

 The oil above mentioned, tested in an apparatus like the 

 old government open, with a screen around and piartly on 

 top, but nine inches in diameter, applying the flame every 

 two degrees, ignited exi^losively at 88° F. and contin- 

 ued to burn furiously. Applying the flame every degree 

 the same result was attained at 87° F. Transforming 

 the apparatus into a closed test, the oil ignited and 

 burned at 76° P. Except, then, for small surfaces, the 

 flash and burning points are the same, and the Abel flash, 

 becomes a jDoint of danger for oil in store, barrel or tin, 

 while for oil in large vessels, tanks, etc., the danger point 

 is still lower. A case is cited where a large tank of very 

 high flashing oil was being jjumped into, the temperature 

 being far below the flash point in Abel cujj, vapors were 

 evolved, overflowing through an imperfectly closed manhole 

 at the top, and were ignited at a lamp some distance below. 

 The fire ran back; an exj)losion resulted, blowing off the 

 top of the tank, and the oil was burned. It is curious 

 to note that while the British Government fixes the flash 

 test at 73'' F. for the public, it places the same at 105° F. 

 for its own governmental departments, and at 145° F. 

 for the lighthouses. 



Extraction of Fat from Feeding Cakes. 

 The extraction of fat from fodder by means of anhy- 

 drous ether, after a preliminary drying, or even with low- 

 boiling petroleum, is known to be unsatisfactory. To 

 avoid the simultaneous extraction of coloring matters, 

 resins, waxy impurities, etc.. Dr. L. Gebek has conducted 

 experiments, using burnt gypsum mixed with the sub- 

 stance to be extracted, also filtering the ethereal solution 

 through a gypsum filter. Finely powdered gypsum be- 



