Repository: UIHistories Project: Board of Trustees Minutes - 1880 [PAGE 108]

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106 The largest specimen measured one inch in height and three inches in shortest diameter. The smaller specimens, however, were more perfect in their crystalization, and the angles on them could be measured with a tolerable degree of accuracy. The form of the crystals resembled a combination of the rhombic prism with a brachy-pinakoid and a basal-pinakoid. The brachydiagonal angle of the prism measured 129 degrees. The angle formed by the intersection of a face of the prism with that of the brachy-pinakoid corresponded, within a fraction of a degree, to the calculated value 115 degrees and 30 minutes. The chemical composition of the mineral is as follows: Calcium carbonate. .. Magnesium carbonate Ferric oxide Silicious matter ...95.30 . . . . 1.19 . . . . 2.18 -_-- 0.87

ON THE "FLASH TEST" OF KEEOSENE.

BY HENRY A. WEBER, P H . D.

Explosions of lamps or vessels containing kerosene are caused by the ignition of explosive, gaseous mixtures, with which the lamps or vessels are partially filled. These explosive mixtures consist of air and the vapor of a portion of the kerosene. The natural coal oils consist of a variety of hydrocarbons,» differing widely in regard to their boiling points. In the process of refining, the hydrocarbons which have a low boiling point are supposed to be separated from those having a higher boiling point. The latter form the kerosene of commerce. The oils of a low boiling point, however, have always been imperfectly separated from the kerosene, by the refiners, and to this neglect the many sad accidents caused by the explosion of lamps and oil cans is due. To protect the people against this abuse, many States have passed laws requiring the dealers to sell only those grades of kerosene which give off no inflammable vapor under a fixed temperature, which in our own State is 150 degrees Fahrenheit. The temperature at which, kerosene gives off an inflammable vapor is determined by what is known as the "flash test." This test is applied in various ways. One method consists in placing a few ounces of the kerosene in a shallow porcelain dish, and heating the oil on a sand bath. While the heat is applied, a burning taper is passed to and fro about four inches above the surface of the oil until the vapor given off ignites or "flashes." The temperature at which this takes place is shown by a thermometer, whose bulb dips in the heated oil. If it is borne in mind that the most highly combustible gases do not ignite when mixed with an undue proportion