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ing of fifty years ago. This process has been made as sure and as simple as any in the tannery by the use of uniformly stable emulsions of scientifically selected oils and by the control of the nature and amount of soluble matter carried into the fat-liquor by the leather through proper regulation of the tan liquors. I n coloring, the changes have been largely in the substitution of aniline dyes for the natural dyestuffs formerly used and in the selection of mordants and control of pH value and temperature. Modern leather shows an advantage over leather of fifty years ago, not only in the variety of shades available, bht also in the clearness, uniformity, and permanence of color. Great strides have also been made in the preparation of finishing or sizing materials and in methods of applying them to the leather.
5-01. 18, KO.9
Scientific Control Fifty years ago tanners had no chemical laboratories, but today in a large and progressive tannery one may find five or six separate laboratories devoted, not only to routine analyses, but to research dealing with pure physical chemistry, colloidal phenomena, bacteria, enzymes, proteins, tannins, oil emulsions, histology of skin, photomicrography, and to many phases of chemistry not ordinarily taught at the university. These laboratories are continually throwing new light upon the processes, making more rigid the systems of control, and actually developing new methods. Although fundamentally the processes are similar today to those in use in 1876, the development of scientific control of those processes has resulted in practical advances in leather-making that are nothing short of phenomenal.
Fifty Years in the Petroleum Industry' By Frank A. Howard STANDARD DEVELOPMENT C O . ,NEWYORK,N. Y.
T
HE first important product made by distilling petroleum was kerosene. It was quickly found that this
needed some purification in order to make it burn satisfactorily in lamps with wicks. The first refining agents used for purifying kerosene distillates were lime and caustic alkali. These were not satisfactory, however, since kerosene refined in this manner causes a crust to form on the lamp wick and causes clogging. The value of treating kerosene with sulfuric acid followed by a caustic soda wash was accidently discovered in 1852 in an apothecary in Galicia, where two assistants named Lukasiewicz and Zeh treated some petroleum distillate in this manner and found that the treated oil burned well in a lamp. Prof. Benjamin Silliman, Jr., BS early as 1855, used sulfuric acid in refining the distillates which he obtained from a sample of Pennsylvania petroleum, and Professor Eichler is said to have introduced into Russia the use of sulfuric acid followed by neutralization with caustic soda. This method of refining kerosene was, therefore, known fifty years ago and is still in general use today for treating both light distillates and lubricating oils. Composition of Crude Petroleum
The action of sulfuric acid as used in the purification of petroleum distillates and residual oils is not fully known and must vary considerably with products from crudes of widely different origin and chemical composition. Many different types of chemical compounds are found in crude petroleum and more are produced as secondary products when oil is subjected to cracking processes. I n addition to saturated hydrocarbons, crude petroleums contain aromatic and naphthenic ring hydrocarbons, both types of which may have side chains attached to the rings. Certain gasoline distillates contain more than 50 per cent of these two types of hydrocarbons and one crude petroleum has been encountered which gave a natural gasoline distillate containing approximately 70 per cent of naphthenes. Distillates from cracking processes contain unsaturated hydrocarbons such as olefins and diolefins. Crude petroleum also contains sulfur compounds, the type and quantity of which vary greatly with the origin of the various crude oils. Mercaptans are common in most crudes, but in addition to these there may be found many other classes of sulfur 1
Received July 28, 1926.
compounds, some of which require special methods for their removal. Pu'itrogen compounds are found in some crudes and in rare cases may be present to the extent of several per cent. Oxygen is present in many crudes in the form of organic acids. The most common of these are the so-called naphthenic acids, which exist in the naphthene base crude found in many parts of the world, and which are highly resistant to the action of sulfuric acid. While there may be some doubt as to the exact constitution of the naphthenic acids and while they vary widely in molecular weight and structure, they contain one or more carboxyl groups and can, therefore, form soaps with alkalies. Refining Agents
SULFURICACID-The foregoing brief statement of some of the types of compounds in crude petroleum will serve to show how much work is expected of sulfuric acid when it is used as a general refining agent. Sulfuric acid acts as a purifying agent of petroleum products in the capacity of a solvent of certain impurities such as tars and by direct chemical action on different groups of compounds, among which are the olefins and aromatics. It also acts as an oxidant on some petroleum compounds, as evidenced by the sulfur dioxide which is evolved during the treating process. One of the main functions of the acid is to remove sulfur compounds from petroleum, Although new methods of treating petroleum distillates have been introduced during the last fifty years, there is no doubt that sulfuric acid is still the most important reagent in petroleum refining. Certain crudes, such as the Lima of Ohio and some found in Canada, contain sulfur in such a combination that sulfuric acid is not effective for purification. For the treatment of these crudes Herman Frasch invented the Frasch process for the desulfurization of kerosene. This process consists in distilling the kerosene with large quantities of copper oxide. This procedure desulfurizes the oil from 0.75 to 0.02 per cent and removes the skunk odor which makes such oil unsalable. The introduction of the Frasch process increased the price of Lima crude from 14 cents to $1.00 per barrel and made it possible to produce kerosene of a Pennsylvania grade from this bad crude. DOCTOR SoLuTIox-One of the most widely used refining
September, 1926
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agents introduced into the petroleum industry within the years in oil refining, primarily for reduction of sulfur, allast fifty years is the so-called “doctor” solution. This is a though decolorizing, deodorizing, and polymerization or solution or suspension of litharge in aqueous caustic soda removal of highly unstable bodies are also effected, to varying and is used for deodorizing oil and removing certain types degrees. I n the field of decolorizing and filtration, in general, of sulfur compounds. It is also used as a test in the laboratory fuller’s earth remains the standard of the refining industry. Particularly on the California coast there has been a in order to determine whether or not petroleum products are “sweet.” The doctor solution indicates the presence growing use of specially prepared or activated decolorizing of hydrogen sulfide and mercaptans and certain polysulfides materials. Percolation filtration is still the standard practice, and cannot be used to indicate the total quantity of sulfur but both fuller’s earth in a finer state of subdivision and the present, since a petroleum distillate which may be sweet more active special decolorizing clays are now used in cont o the doctor may contain a high percentage of sulfur in such tinuous systems in which the finely divided clay is first agia chemical combination that it does not react with the doctor. tated with the oil and then filtered out in a filter press. A comparatively recent commercial development in the ALUMINUMCHLORIDE-The treatment of hydrocarbons with anhydrous aluminum chloride was suggested by Friedel use of fuller’s earth in petroleum refining is the employment and Crafts as early as 1878, but until recent years this proc- of specially designed vapor-treating towers, in which the ess has not operated on a commercial scale. When alu- vapors of light distillates of petroleum, particularly cracked minum chloride is added to petroleum or petroleum dis- distillates, are caused to pass downwardly through a bed tillates, certain hydrocarbons combine with the aluminum of fuller’s earth, the mechanical arrangement being such that chloride, forming compounds which separate from the oil the polymerized bodies separating out as a liquid in the as a dark sludge. This reaction is accelerated by heating. passage of the vapor through the clay are trapped out, When a mixture of aluminum chloride and oil is distilled permitting the uncontaminated vapors to pass to the conthe aluminum chloride-hydrocarbon compound.j break up, denser. The condensate from cracked vapors treated in giving hydrocarbons of lower boiling point than those in this manner exhibits a considerable degree of stability, the oil used. This process may be run a t atmospheric or indicating a n efficient selective polymerization action exhigher pressures, and even under a vacuum. It is used ercised by the fuller’s earth under these conditions. This primarily as a cracking process. Under certain conditions process bears the name of the patentee, Thomas T. Gray, very light cracked naphtha containing a high percentage and is so identified in the petroleum trade a t the present time. of olefins when treated with aluminum chloride will polymCracking erize the olefins to such an extent that there will be a considerable yield of lubricating oil. Aluminum chloride also From the standpoint of economics, by far the most imdesulfurizes practically all types of petroleum distillates, portant development in the petroleum industry during even those that are very resistant to sulfuric acid. the past half-century has been the development of pyroSULFURDrosmE--The use of liquid sulfur dioxide in genetic cracking to produce motor gasoline from heavier treating petroleum distillates has been introduced by Dr. oils of lower market value. The fundamental action is Edeleanu. This is essentially a solvent method. The chemical, since the change produced is a true chemical change. sulfur dioxide has a useful selective action on aromatics It is probably fair to say that the chemists have contributed and certain unsaturated hydrocarbons. By this method more than any other profession to the advance of this devery smoky kerosene can be treated so as to produce a very velopment. The chemical problems which arise are not satisfactory illuminant. Crude oils which are rich in aromatic confined to the control of the cracking operation itself, compounds are found in many parts of the world and in this but follow through to the efficient handling of the products country the kerosene fractions of many California crudes produced to make them conform to accepted standards cannot be effectively treated with ordinary amounts of based upon characteristics of natural petroleum distillates. sulfuric acid. Hence sulfur dioxide is used in some CaliMotor Fuels fornia refineries for treating kerosene. I n this process there is very little loss of sulfur dioxide, since it is recovered The study of the chemical properties of motor gasoline and used again. The residual oil, after evaporating off and various blending agents, particularly benzene and its the sulfur dioxide, contains a high percentage of aromatic lighter homologs and the lower alcohols, used together with hydrocarbons. gasoline for the production of blended motor fuels, as related HYPOCHLORITE-There has recently been promoted in to the combustion characteristics of the fuel, has been the England a process for treating petroleum distillates which subject of intensive research. Paralleling this line of inemploys sodium or calcium hypochlorite as the treating vestigation, there has been another directed toward disagent. This process is also used to some extent in the covery of compounds which when present in small proUnited States. The oil is treated with a dilute solution of portions would be capable of radically affecting combustion. the hypochlorite in a mechanically stirred agitator, after The result of these lines of work has been the intensive prowhich it is neutralized with caustic soda, washed, and duction of specially blended and specially treated motor filtered through bauxite. It is claimed that this process fuels capable of withstanding engine-compression pressures removes sulfur, but its action in this respect appears to be much higher than those under which ordinary gasoline quite limited. will operate satisfactorily. The most important chemical SILICAGEL AND FULLER’S EARTH-A considerable amount work in this field has been that conducted by Thomas Midgof technical work has been done in the United States in the ley, Jr. This work culminated in the perfection of a development of silica gel as a selective absorbent for oil commercial antiknock compound comprising tetraethyl refining. I t s properties are different from those of the lead as the effective knock-reducing agent in combination fuller’s earth, which has been generally used for decolorizing with auxiliary chemicals, particularly volatile halides, in petroleum oils, particularly the lubricating fractions, as a proportions sufficient to convert the tetraethyl lead comstandard refining process. The special properties of the bustion products into lead halides. The future economic silica gel were most clearly exhibited in the effect on the value of this work promises to be second only to the cracking sulfur content of oils, such as Mexican petroleum. There process itself as a means for effectively increasing the motor has been a limited use of this material within the past five fuel supply. This results from the fact that these specially
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treated fuels are capable of use in automobile engines of efficiency far higher than the average efficiency now obtainable. Scientific Research
The advances in the petroleum industry during the last half-century have been made in spite of the lack of any sustained broad program of pure scientific research, similar to the movement upon which the coal-tar industry and its dependents, the modern dye, synthetic, pharmaceutical, and explosive industries, were founded. ILIr. Rockefeller
Vol. 18, No. 9
having taken the initiative by establishing a fund of $260,000 for the promotion of pure scientific research in fields related to the petroleum industry, it is hoped that among chemists, a t least, petroleum will be a preferred field for investigation during the next generation. Given a foundation knowledge of the chemistry of petroleum and its COQstituents comparable to the existing knowledge of the identity and chemical behavior of the homologs of benzene, i t is hoped that progress will be made a t an accelerated ratecommensurate with the ever-growing importance of petroleum to civilization.
The Cotton Seed and Its Products' By David Wesson SOUTHERNCOTTONOIL Co., NEW YORK,N. Y.
OMEBODY has called the cotton seed the southern
S
farmers' pocket money, because it is the only part of his crop for which he receives ready cash, after he has met his obligations for fertilizer and the necessities of life, against which he has pledged the staple. I n round figures there is a ton of cotton seed for every two bales of cotton made. The cotton is the big crop. At 20 cents per pound, a 500-pound bale brings the farmer one hundred dollars. With seed a t thirty-two dollars per ton, which has been the ruling price during the past year, the seed has been worth sixteen dollars for every bale of cotton grown. I n other words, during the past season the seed was roughly worth about 16 per cent as much as the cotton. It was not always thus. Many people now living well remember the time when the seed was considered a nuisance, and was thrown into the streams or burned, while the more progressive farmers made it into compost and used it for fertilizer. Some of the states passed laws forbidding the throwing of the seed into streams used for drinking water and fishing. I n other places gin owners were fined for allowing the seed to remain in the neighborhood of towns and villages after it had commenced to decompose. Although cotton oil mills were started in various parts of the South early in the last century, it was not till about 1870 that the seed was worked to any extent. I n that year about 4 per cent of the entire seed crop was milled into oil and cake. At the present time about SO per cent of the seed crop goes to the mills, the balance being saved for planting. During the past season the cotton crop was 16 million bales. This would have made about 8 million tons of seed worth something like 256 million dollars delivered a t the mills. Probably not over 6.5 million tons found their way to the oil mills, where it was worked into oil cake, meal, hulls, and linters. Notwithstanding the vast importance and great value of the cottonseed crop, the commercial dealings in the seed have always been carried on under the supposition that seed is seed, and the price has been regulated by supply and demand rather than by the contents of the seed in oil and ammonia, As a result great losses have been sustained by the mills and unfair receipts by the farmers who, selling on this basis of supply and demand, frequently obtain better prices for poor seed than for that rich in oil. The intelligent mill owner can protect himself to some extent 1
Received July 17, 1926.
by obtaining seed analyses on the seed from various districts and buying only from those districts where the seed shows a good percentage of oil. The composition of the seed is affected by character of the soil, fertilizer used, weather, and the closeness with which it is ginned. The more staple removed in the ginning the smaller the percentage of hulls and the higher the percentage of meats. The Department of Agriculture has been making a careful investigation of the practicability of grading cotton seed in the same manner as corn and wheat. I n a very interesting report before the Interstate Cottonseed Crushers Convention in New Orleans, May 13, 1926, G. s. Illeloy, of the Bureau of Agricultural Economics, bases his grades on the assumption of the proportional ralues of the various seed products as follows: oil 52.5, meal 34.5, hulls 7.1, linters 5.9 per cent. He gives tables showing percentages of meats running from 41 to 60 per cent with oil ,n meats running from 33 to 39 per cent, or from 270.6 pounds to 468 pounds of oil per ton of seed. With these enormous variations it is evident that the mill manager who does not know the content of his seed is buying a pig in a poke. Milling
I n the operation of milling the seed is first cleaned by passing over shaking screens to remove the sand and trash and then over magnets to remove the nails and pieces of iron that are often present. The cleaned seed then goes to the linter, which is a kind of gin for the removal of the short staple left on the seed by the cotton gins. The amount of lint removed depends on the demand and also on how closely the seed was ginned before delivery to the mill. Where a very long staple is desired, only 20 or 30 pounds of lint are cut per ton. Such linters can be worked into yarn and bring a high price. Ordinary practice, however, is to cut 50 to 75 pounds per ton. Such lint is short of staple and contains more or less hull particles. During the war it was common practice to cut from 100 to 150 pounds of lint per ton. This contained considerable impurity which did not interfere with working up the lint with caustic soda and chlorine for munition purposes. When peace was declared, large quantities of this lowgrade lint, left on hand a t the mills, was worked up for paper stock of a choice quality which competed with that made from rags. After the war there was a demand for better quality lint and when the munition linters were exhausted the paper stock manufacture died a natural death.
