SHALE OIL PRODUCTS. SHALE SPIRIT. Gasoline of specific gravity ·640 to 660, and naphthas of specific gravities 718 to 720, 735 to 740 and 750 are manufactured at some works. The flash-points of the various descriptions of shale spirit are below the legal standard. The oils for use in lamps, sold under the names of "paraffin oil," "burning oil," "crystal oil," "petroline," &c., usually have a specific gravity of about 810, and a flash-point of 105° F. (Abel) and upwards. A special oil for use in lighthouses is also manufactured with a specific gravity of 814 and a flash-point of 145° F. (Abel). Another product, of still higher specific gravity (about 836) and flash-point, is termed "marine oil." The specific gravity of intermediate oil or gas-oil produced from shale ranges from 840 to 865 and the flashpoint from 150° F. (Abel) upwards. Lubricating oils of various specific gravities and viscosities, as well as soft and hard paraffin, are among the products obtained. COAL-TAR PRODUCTS. It is only necessary in this statement to mention the various naphtha-products.* These include benzene (benzol), the hydrocarbon CH, which has a specific gravity of 884, a boiling-point of 177° F., and a flash-point below the temperature of 32° F. at which it solidifies; toluene (C,H), specific gravity 871, boiling-point 232° F., flash-point about 45° F.; solvent naphtha (often described as having a specific gravity not above 875 and as distilling between 248° and 320° F.), specific gravity often about 867, and flash-point about 66° F.; heavy solvent naphtha or burning naphtha (sometimes described as having a specific gravity of 880 to 887), specific gravity often as high * The so-called "sharp oi!," used in lamps of the "lucigen" type, has a specific gravity of about 1060, and a flash-point of about 160° F. as 905, and flash-point about 116° F.*; 90 per cent. Note.-" Benzine Collas" is a name under which a description of mineral spirit, doubtless obtained originally from coal-tar, has been sold for detergent purposes for many years. (The label used includes the copy of a testimonial from the Master of the Royal Apartments, dated Buckingham Palace, October 30, 1858.) In order to show the relative extent to which various descriptions of petroleum products occur in commerce in this country, statistics of imports are given in Appendix I. uses of petroleum increasing. The employment of petroleum products as liquid Various fuel, as a substitute for coal in the manufacture of gas for illuminating and heating purposes, as a source of products power in internal-combustion engines, and as lubricants, is rapidly increasing as the attendant advantages become recognised, and adequate supplies are rendered available. An impetus has also recently been given to the use of kerosene as an illuminating agent, for it has been demonstrated that when burned in a specially constructed mantle lamp in the form of vapour, under pressure, a brilliant light, well adapted for streets and large buildings, can be obtained from this oil at a less cost than by the use of any other illuminating agent, and as each lamp is self-contained the installation of the system can be effected without any opening of the ground such as is necessary in laying a service of gas-mains. There is, therefore, reason to anticipate further vigorous growth of this already highly important industry. mantle-lamp * Two descriptions of solvent naphtha are specially prepared which have flash-points a little above 73° and 100° F. respectively. These products have specific gravities ranging from 890 to 915, according to the character of the tar from which they are manufactured. of flash point. CHAPTER V. "FLASH-POINT" AND "FIRE-TEST." Explanation THE Petroleum Acts are made to apply to such petroleum as, when tested in the manner prescribed, "gives off an inflammable vapour" at a temperature of less than 73° F. This wording is unfortunate, inasmuch as it has given rise to a great deal of misconception as to the real meaning of the term "flash-point," and as to its relation to the safety of an oil in storage and use. In the succeeding chapter, the various methods of testing petroleum for the determination of its flashpoint are described in detail. It is, therefore, only necessary here to enunciate the broad principle on which all such tests are carried out. A sample of the oil to be tested is placed in a vessel, and is gradually heated up until, on application of a light, a blue flame or flash is seen in the space above the surface of the liquid. The temperature of the oil at this point is noted, and this temperature is now comn.only called the "flash-point" of the oil. The Act of 1879 and all previous ones, however, call this the temperature at which the petroleum "gives off inflammable vapour." This has led many persons to suppose that at this temperature the oil undergoes some physical change, and suddenly commences to evolve vapour. As a matter of fact, like all other liquids, petroleum gives off vapour at all temperatures, and would continue to do so even if cooled down to zero Fahrenheit. What the Act really means is the temperature at which the oil gives off, or has given off, sufficient vapour to form an inflammable mixture with the air, and this is a matter entirely dependent on the conditions under which the test is carried out. By varying these conditions very wide differences may be made in the flash-point obtained with one and the same sample of oil. Consequently, to speak of the flash-point without naming the method by which it is to be determined is as meaningless as to name a degree of temperature without stating whether the Fahrenheit or Centigrade thermometer scale is intended. This fact appears to have been unknown to the framers of the Petroleum Act, 1862, in which a flash-point is specified, but no method of determining it is prescribed. In the subsequent Acts of 1868 and 1871 a test apparatus is laid down, but it was not until 1879 that the Legislature adopted a method, known as the Abel test,* in which the conditions are so far under control that anything like uniformity can be obtained in the hands of different experimenters. Further experience has, however, shown that still greater uniformity can be obtained by improvements in this instrument and in the method of its employment. of vapour The minimum proportion of vapour to air necessary Proportion. to produce an inflammable mixture is about 18 per necessary to cent. An increase to 2 per cent. of vapour renders form the mixture explosive, while when the proportion explosive exceeds about. 4 per cent., the liability to explosion the air. begins to disappear, but the mixture continues to be inflammable. Now, not only does the temperature at which an oil gives off sufficient vapour to produce such proportions depend on many conditions, but the percentages themselves are also liable to variations. It will be sufficient to discuss only the more important causes which are *See Appendix II.. mixture with affecting flash-point. of vapour. known to produce such variations, but there are doubtless many other conditions which have a more or less direct influence both on the temperature and the percentage One of the most important conditions Conditions affecting the temperature at which an inflammable mixture of vapour aud air may be produced, is the time during which the oil has been submitted to that temperature. As has already been pointed out, no ordinary sample of petroleum is homogeneous, and it is the vapour of its lighter and more volatile constituents which is first given off. If the proportion of light constituents is small, their vapour will be given off slowly, and it may take a very long time before a sufficient amount has been evolved to render a given volume of air inflammable. Consequently, in a closed vessel, if sufficient time is allowed, the vapour may continue to accumulate until an explosive atmosphere is formed, even though the oil may never have reached a temperature as high as that of its flash-point determined by a test where the time is limited. On the other hand, if the oil is contained in a vessel which is not completely closed, the effect of time may be just the reverse of that described. Thus, if the test is carried out in an open or partially open vessel, and if the rate of heating is made very slow, much of the vapour given off in the earlier stages of heating will diffuse into the outer air. In this way the proportion of lighter spirit will be diminished, and the flash-point determined by such a test will be higher than if the rate of heating had been more rapid. It is hardly necessary to state that the flash-point is very largely affected by the amount of ventilation which is afforded to the sample in the testing apparatus. The very wide difference between the results obtained with the test prescribed in the Act of 1871 and those of the Abel test, are principally due to the fact that in |