Popular Science Monthly/Volume 27/June 1885/Concerning Kerosene
By Professor S. F. PECKHAM.
A MODERN French writer has said: "In the domain of the useful arts each age reveals characteristic tendencies. In the last century, mankind had need to clothe itself cheaply. . . . The nineteenth century has wished for light." To the development of the petroleum industry the gratification of this wish is mainly due; yet, while the products of petroleum are used in nine tenths of all the dwellings of the land, but few of those who occupy them realize that 60,000 barrels of crude oil flow from the earth every day, that more than 30,000,000 barrels are now stored above-ground in huge iron tanks, and that 15,000 barrels are required to supply each day's demand in the United States alone. Of this vast quantity, by far the largest proportion is consumed as illuminating oil, or kerosene, for the production of which a stream of oil is constantly flowing through six-inch pipes from the oil-region of Western Pennsylvania to Baltimore, Philadelphia, and Jersey City. In each of these cities establishments, constructed for the purpose, convert the crude oil into various products, principally illuminating oil, for the home market and an export trade of vast proportions. In these refineries the oil is first allowed to settle in large tanks, in which a small percentage of water and sediment accumulates. From these tanks the oil is pumped into stills, holding about 1,200 barrels each, beneath which fires may be kindled, and urged by a strong draught until a red-heat is attained.
Petroleum consists of a great many different fluids, which range in volatility from the boiling-point of ether to nearly a red-heat. Such being the case, as soon as the oil is heated at all, the most volatile products begin to come over, at first colorless as water, but very gradually assuming a yellow tinge until the most dense distillate coming over at the last is quite dark brown in color, so that, if all the distillate were allowed to run into a tank together, it would not look very differently from the original petroleum. In the ordinary process of refining petroleum, the distillate is divided into three portions. The first is the lightest, colorless portion, nearly as volatile as ether, and is called crude naphtha, or "benzine." Like the crude petroleum, this crude naphtha may be distilled and divided into gasolene, A, B, and C naphtha, which are used in gas-machines, for mixing paints, and other similar purposes, sometimes also for burning in lamps and stoves.
The middle portion of the distillate, which is neither very light nor very heavy, and having but little color, is the crude illuminating-oil, or kerosene. As it runs from the still it has a very offensive odor, due to the decomposition of certain portions of the petroleum at the high temperature reached in the still. To remove the offensive compounds, the oil is first agitated with about five per cent of strong oil of vitriol. This combines with the offensive oils, forming a black, tarry residue that falls to the bottom of the tank as soon as the oil is brought to rest. This mixture of acid and oil is called "sludge," and is used in large quantities in the manufacture of commercial fertilizers. After the acid is drawn off and the oil washed with water, it is again washed with a strong solution of caustic soda, which removes the excess of sulphuric acid, and also some peculiar acid compounds that exist in the oil. The oil, after another washing with water, is nearly colorless, with the peculiar balsamic odor of kerosene, and possesses the slight opalescence peculiar to these oils. As usually prepared, they belong to the class known as "high-test" kerosenes, and consist almost entirely of oils that exist in the petroleum already formed, being merely separated from the lightest and heaviest portions. Such oils are called the educts of the petroleum.
The heaviest portions of the distillate contain paraffine, and are called paraffine-oils. They also are mainly educts of the original oil; they, however, contain a much larger proportion than the kerosene of the products of the decomposition of the oil. A tarry residue remains in the still, called "residuum."
In other establishments the naphtha and illuminating oil are distilled from the petroleum, and the dense oil remaining in the still, called "reduced petroleum," is drawn out and used for lubrication. A large part of this dense oil from which the naphtha and illuminating oil have been removed is "cracked," or destructively distilled, by slacking the fires, and allowing the distillation to proceed so slowly that the dense portions of the vapors are condensed on the dome of the still, and, falling back upon the surface of the hot oil, are heated above their boiling-points, and decomposed into a lighter oil and a carbonaceous residue. By continuing this process for several hours the oil has passed out of the still, leaving a quantity of residuum, as in the first instance. This cracking process is never complete, as a portion of the oil is cracked too much and another portion too little; but the average gives a burning-oil of the proper density, color, etc., while in other respects it is greatly inferior to the oil that is not cracked. The reader will readily perceive that by mixing these constituent oils of the petroleum suitable for burning-oil, which have been very properly called "normal" burning-oils, with different proportions of the cracked oils, a great variety of products may be obtained; but I propose in this article to speak of only three classes of burning-oils, and to show that these three classes may furnish oils that meet the demands of legal enactments, while at the same time they may be both very dangerous and very bad.
The first class of oils mentioned that are distilled from the petroleum unchanged consists of compounds of hydrogen and carbon combined in such proportions that the percentage of hydrogen is greater than in any other similar substances. In addition, they are very inert to chemical reagents, in this respect resembling paraffine or India-rubber. They may be washed with sulphuric acid or strong solution of caustic soda, and very completely purified; but they are not acted on by either of these powerful reagents, and the product is a pure, colorless oil, with the odor of kerosene, and burning with a dazzling, white flame. The wick is burned but little more rapidly than that of an alcohol-lamp. The flame does not smoke, neither does it emit any unpleasant odor. These oils are safe, healthful, and economical; in fact, they constitute the best and cheapest illuminating agent ever given to man.
When the oils too heavy for illuminating oils are destructively distilled or "cracked," the product is largely contaminated with oils containing less hydrogen in proportion to the carbon, and which are not inert to chemical reagents like those just described. When these oils are treated with sulphuric acid, both the oil and the acid are decomposed. The sulphur and a part of the oxygen of the acid (SO2) take the place of a part of the hydrogen of the oil, while this hydrogen unites with the remaining oxygen of the acid and forms water. This sulphur and oxygen thus become constituents of the oil, and when the oil is burned they escape into the room as sulphurous oxide identical with the fumes of burned brimstone. But this is not all: the sulphur compounds, and the heavy, imperfectly cracked oils, soon impair the capillary attraction of the wick; and, the flow of the oil being impeded, the wick becomes charred and coated with unburned carbon. This imperfect combustion produces smoke and imparts to the atmosphere of the room unpleasant odors, and not infrequently leads to an explosion of the lamp and disastrous conflagrations. The steady flow of the oil through an unencumbered wick keeps the wick burner comparatively cool, and prevents the heating of the lamp and of the oil within it; but, when the capillarity of the wick is impaired, the burner, lamp and oil within it become heated to a temperature that finally produces a distillation of the lighter portion of the oil, in many instances causing the flame to become dense and smoky; sometimes streaming above the top of the chimney; and, if not speedily extinguished, resulting in an explosion and the destruction of the lamp.
When the normal and cracked oils are mixed, the mixture partakes of the mingled characteristics of the constituents. The mixture may be nearly as good as the normal oils, or nearly as bad as the cracked oils. At the present time the common kerosene sold is either a "cracked" or a "mixed" oil, while the bulk of the high-test kerosene is supposed to consist of "normal" oil; and, while any or all of these oils may be of any required test, they are of very various quality in other respects.
The test of an oil, "high" or "low," represents the temperature to which the oil must be heated in order that a suitable quantity—usually one half-pint—may give off a sufficient amount of inflammable vapor to either flash or burn. The temperatures at which the same oil will flash and burn vary greatly with the character of the oil, being from 10° to 50° apart by Fahrenheit's scale. While it has been repeatedly demonstrated, by several of the most eminent scientific experts now living, that the temperature at which an oil will burn is of no importance as an indication of its safety, this test is still in use in many localities. It is, however, the temperature at which the vapors will flash that is usually understood as the "test" of an oil, and it varies from 70° to 90° Fahr. in low-test oils to 120° to 140° in high-test oils. Experiment has repeatedly demonstrated that an oil that will give off vapors that will flash at 100° Fahr. is safe for any legitimate use. As painful and disastrous accidents are liable to follow the explosion of a lamp, and as the increased danger of explosion where low-test oils are used is obvious to any reflecting person, all efforts to restrict the manufacture or sale of unsafe oils by legislation have been hitherto directed toward the exclusion of very low-test oils from the market. In England such legislation has been based upon very elaborate research, and has been in the main successful; but in the United States no less earnest though less carefully considered measures have been embodied in legislation which has resulted in the enactment of a great variety of statutes—giving to some States laws unreasonably exacting, to others wise provisions, while yet others have no legislative restrictions whatever. Of course, such diverse enactments relating to a single interest and question can not command the respectful consideration that uniform, just, and reasonable legislation would receive from all intelligent persons interested; hence, it may be fairly stated that in this country legislation relating to the testing of petroleum is in in many respects unsatisfactory.
It is not, however, to the generally unsafe character of low-test oils that I wish to call attention, but to those characteristics, not yet generally or fully recognized, that render some oils that come within the legal provisions regarding test unhealthy and unsafe for use.
The petroleum industry, in many of its aspects, is the product of development. This statement is true, not only as respects its vast magnitude, but also as pertaining to many of its details. The process of cracking had been employed in treating the distillates from coal before petroleum became an article of commerce; yet petroleum, for a number of years following its discovery in large quantities, was uniformly distilled into naphtha, normal burning-oil, and paraffine-oil. At that time but few uses were known for naphtha, and it was a drug in the market. At the same time the paraffine-oils were contaminated with more or less of the products of destructive distillation that were unavoidable attendants of even rapid distillation. These oils were consequently very poor lubricators, and, moreover, possessed a very unpleasant odor. They never commanded a good price and were slow of sale, for which reason it was obviously the interest of the manufacturer to put into the burning-oil as large a proportion of the naphtha as possible, for the purpose of holding in solution a maximum quantity of paraffine-oil. This often produced an oil unsafe from excess of naphtha, but it was an oil consisting mainly of normal oil, and almost entirely of the educts of the petroleum. Sulphur had not then been observed as an impurity in burning-oil, although the same process of treatment was then used, but less carefully than now. As the original district of Oil Creek produced, at the end of ten years, a smaller proportion of the entire production of crude oil, the character of the burning-oil on the market in 1875 was different from what it was in 1865. At the former date the "lower country," so called in Butler and Clarion Counties, yielded an oil in some respects different from that of Oil Creek, and unequaled for the manufacture of burning oil, inasmuch as the percentage of normal oils suitable for burning was found to be considerably greater. In five years the diminished production in the Butler-Clarion field, and the increased production of the Bradford district, together with the mixing of the entire production in huge tanks and pipe-lines without regard to quality, had entirely changed the relation of the amount of normal to that of cracked and mixed oils. The vast production and low price of crude oil had thrown the manufacture of petroleum into the hands of corporations controlling immense capital, and establishments in which the oil is handled in quantities proportionate to the enormous demand. Meantime a method of refining petroleum bad been generally introduced, by which a large proportion of the total burning-oil produced consisted of mixed or cracked oils. Such a proportion of high-test oils as were demanded by the market was made, but the great bulk of the distillate had been converted into a cracked or mixed oil. The petroleum was distilled but once, the naphtha was removed, and then the remainder of the oil manipulated to produce such crude burning-oils as were desired, leaving in the still only a small percentage of residuum. These crude burning-oils were treated with sulphuric acid and caustic soda in such a manner as to produce the lightest colored oil possible, and they were further manipulated to bring the test within the legal requirements. As it was much less difficult to bring the mixed or cracked oils within the requirements of a burning rather than a flash test, the burning test has always found strong advocates among a certain class of the manufacturers of petroleum. This method of manufacture was well established, and the markets of the world were well accustomed to handling the various products during that period when the bulk of the crude oil came from the Butler-Clarion district. But gradually, as has been stated, the major portion of the crude oil that flowed into the pipe-lines was no longer from the Butler-Clarion wells, but from those of Bradford. By the end of 1881 more than three quarters of the crude oil was Bradford oil, and the relative proportion has steadily increased. This change in the crude material has been accompanied by a corresponding change in the character of the product. Instead of mixed and cracked oils, consisting largely of normal burning-oil, the products of Bradford crude oil consist largely of the products of destructive distillation, and this is due to the fact that the petroleums of the Butler-Clarion and Bradford districts represent two extremes; the first contains the smallest proportion and the latter the largest proportion of paraffine-oils of any crude petroleums found in large quantities. The proportion of cracked oils in the distillate from the Butler-Clarion petroleum was too small to injure the general quality of the oil. In the Bradford distillates, on the contrary, the products of destructive distillation give character to the whole. And not only is this statement true, but the proportion of high-test normal oils to be obtained at present from the pipe-line crude oil has gradually become so reduced that the best brands of oil on the market have deteriorated, until it is very difficult, if not impossible, to purchase an article of burning-oil equal in quality to the best offered for sale a few years since. All this time the requirements of law in regard to test have been met, perhaps it may be said, with increased faithfulness.
From the foregoing pages it must be manifest that any improvement in the increasingly bad quality of kerosene can be looked for only from one of two directions. Either it must come from the development of a new field for crude oil of superior quality, or from the introduction of new methods of manufacture. There are no indications at present that warrant any expectation that any material change is imminent in the character of the crude oil. The change must, therefore, come from the introduction of different methods of manufacture. These methods need be neither novel nor unreasonably expensive. Cracked oils of good quality are nothing new, but I have never seen them made by one distillation and one treatment. Cracked oils should be finished by distillation, not treatment. A second distillation would enable the refiner to first remove the two volatile products of cracking and the heavy, uncracked portion of the paraffine-oil, besides destroying the sulphur compounds. But such a technology would so far increase the cost of the oil that those employing it could not compete in the market with those who did not, except by virtue of the superior quality of their oil.
It is in respect to this difficulty that the public weal could be well served by judicious legislation that in its broadest sense might well be considered sanitary legislation. It is a proper subject for physicians to determine, what the precise effects upon the general health may be resulting from the combustion in lamps and stoves of the vast quantities of inferior oils that are daily consumed throughout the country. That the effect must be bad, determining a tendency to certain forms of disease and aggravating others, can not fail to be apparent to the most unreflecting person, especially when it is considered in how few instances any means are employed to remove from the apartment in which these oils are burned the products of combustion. When under such circumstances a pure oil is burned into pure water and carbonic acid, the atmosphere receives a sufficient burden; but when to these are added vapors of burned sulphur and a variety of irritating vapors with smoke, the eyes, lungs, and nostrils pay a heavy tribute. Added to this is the new source of danger from fire resulting from explosions arising from imperfect combustion—a source of danger not hitherto recognized in legislation, but of not infrequent occurrence.
For the reasons stated, it appears that the health and safety of the public, and the protection of those manufacturers who would make a radical change in the methods of manufacture now employed, alike demand legislation that will exclude from the market not only oils that are unsafe from excess of naphtha, but those which in their general character are unhealthful to use and unsafe from other causes. Such legislation should be based upon an exhaustive scientific examination of the subject, with a view to placing the fewest restrictions upon the manufacture and sale of these oils consistent with the demands of public health and safety. Such an investigation can best be undertaken by the General Government, to be followed by such amendments to the national legislation now in force as the results might justify. Such national legislation, based upon a comprehensive knowledge of the subject, could not fail to be followed by a general revision of State and municipal legislation throughout the country and the enactment of uniform laws that, while securing the adequate protection of the public, would no longer embarrass by needless and unreasonable requirements the manufacture and sale of articles in universal demand.