JULY 15, 1936
ANALYTICAL EDITION
Steenbock unit daily. The results of this series, presented in Table 111, series 2, show that the response obtained with these two preparations was identical. As the dosages of 0.025 to 0.0825are in the ratio of 1to 3.33, the results confirm the ratio obtained in the previous series. (Russel and Taylor, 6, have reported, while chis manuscript was being prepared; that one Steenbock unit is equivalent to 3.2 International units.)
Summary 1. One International unit of vitamin D was synthesized from ergosterol when 900 ergs of ultraviolet eneigy within the synthesizing region were absorbed. Similarly, one Steenbock unit was synthesized when 3000 ergs were absorbed. These values were found to be independent of the wave length within the synthesizing region. 2. A comparison of the energy equivalents of the two units, as obtained in independently executed series of assays, and potency Of the Interdirect Of the national Standard Preparation with a preparation produced
293
by a measured amount of monochromatic ultraviolet revealed that one Steenbock unit of vitamin D is equivalent to 3.33 International units.
Acknowledgment The authors acknowledge their indebtedness to Farrington Daniels for helpful counsel in the experimental work. Literature Cited (1) Daniels, F., and Heidt, L., J . Am. Chem. SOC.,54, 2381 (1932). (2) Fosbinder, R. J., Daniels, F., and Steenbock, H., Ibid., 50, 923 (1928). (3) Hess, A. F., and Anderson, R. J., J . Am. Med. Assoc., 89, 1222 (1927). (4) Kon, S. K., Daniels, F., and Steenbock, H., J . Am. Chem. SOC.,50, 2573 (1928). (5) Marshall, A. L., and Knudson, A,, Ibid., 52, 2304 (1930). (6) Russel, W. U., and Taylor, M. W., J . Nutrition, 10, 613 (1935). (7) Steenbock, H.. Kletsein. S. W. F.. and Halpin. J. G., J . B i d . Chem., 97, 249 (1932). RECEIVED February 6, 1936. Published with the permission of the Director, RTisconsin Agricultural Experiment Station.
The Smoke Tendency of Refined Kerosene and Its Determination JOHN B. TERRY
AND
EDWARD FIELD, Standard Oil Company of California, San Francisco, Calif.
B
EFORE the present century, kerosene was not so well refined as it is now, various types of crude oils being used for its manufacture, often without segregation. The product sold varied widely in such characteristics as viscosity, capillarity, boiling range, and sulfur content, all of which are now closely controlled. The researches of Edeleanu were of inestimable value in showing that the aromatic hydrocarbons, which are removed from the crude kerosene by his well-known sulfur dioxide process, were responsible to a large extent for smoky flames, the removal of such compounds resulting in much larger flames having greater luminosity. Even though much better grades of kerosene have been marketed during the last 25 or 30 years, it is only within the last 15 years that attention has been paid to the quality of kerosene as judged by its tendency to smoke (1, 4, 7 , 8, 9). Burning tests have been devised and standardized with a view to determining oil consumption, wick incrustation, chimney fouling, and luminosity (candle power), all of which have produced very enlightening and indispensable information concerning quality. Oils are usually tested in lamps of varying design, depending on the particular purpose for which the oil is to be used. Lamps for such burning tests are not well adapted for smoke tendency tests because chimneys and flames differ in shape and size, so that grading of the oil is rendered difficult; large round wicks 2 or 3 inches in diameter, which are very susceptible to “pitting,” are often used; a considerable personal element is introduced; it is difficult, using such lamps, to grade oils to detect small differences in refinement; and test lamps of the same type are apt to vary when made by different manufacturers, so that an oil may burn with a different efficiency in two supposedly similar lamps.
Development of Smoke Tendency Tests In recent years, investigations of the chemical constitution of kerosenes of different degrees of refinement have shown that the constitution of any kerosene is closely related to its tendency to smoke in a given lamp. This is well illustrated
by the work of Minchin (6, 6) who states that the tendency to smoke is directly proportional to its aromatic or naphthene content. I n the case of homologous series, the tendency to smoke, with the exception of the paraffins, decreases with the increase in the number of carbon atoms or boiling point. The naphthene class has a flame height about three times that of the aromatic, and the paraffin about nine times that of the aromatic, Jackson (3) has further pointed out that a satisfactory test for smoke tendency gives all we need to know for test purposes regarding the percentages of aromatics, naphthenes, and paraffins present in the kerosene. Therefore, a reliable test for smoke tendency would be of great value in controlling the burning qualities of illuminating oils. On the basis of experimental work done in England, the Institution of Petroleum Technologists has standardized on a smoke point test for kerosene tZ), I. P. T. Serial Designation K.36.
Davis Factor Lamp I n the United States, similar experimental work has been proceeding for more than 10 years. One of the earliest lamps to be developed was the Davis factor lamp (Figure l), designed in 1923 by R. F. Davis of the Standard Oil Company of California. The basis of its design was that as increased refinement enables a given kerosene to burn with a higher flame in any one lamp without smoking, a lamp which produced a long narrow flame would be adaptable for control of refinement. The tall flame would be sensitive to oils differing by small increments of refining, and the heights of such a flame could be accurately read and would give a good index of quality. The original design of this lamp included a brass fount of approximately 4-ounce capacity, and regulating wick gears actuated by a larger milled wheel. A special cylindrical glass chimney 7 inches long, 1 inch in outside diameter, and graduated in tenths of an inch was mounted on a brass screen which allowed entrance of air t o the flame. In making a determination, the flame was turned up until a “tail” of smoke just appeared. The flame was then slowly turned down until this tail just disappeared,
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INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 8, NO. 4
Reproducibility With care and proper attention to details, results on duplicate samples of inferior and well-refined kerosenes should agree within 0.05 inch in flame height; with very highly refined kerosenes within 0.10 inch. This degree of accuracy will be obtained only if different lamps are as nearly identical in construction as possible. The main variable in a lamp of this kind is the glass chimney, and in the manufacture of this equipment chimneys should be choEen which give identical results. The screen should be kept clean a t all times; otherwise the volume of air to the flame will be reduced with corresponding reduction in-flame height.
Significance
FIGURE 1. DAVISFACTOR LAMP *
the height of the flame being read on the chimney and recorded. A Handlam long-time-burning felt wick, 0.25 inch in diameter, was used. This lamp gave fairly reliable results, though not entirely satisfactory, and later modifications were made.
Improved Factor Lamp The improved factor lamp (Figure 2) consists of the following: approximately 4-ounce capacity. Regulating BRASSFOUNT, wick gears are enclosed in the brass housing. BRASSSCREEN, aO-mesh, allows entrance of air at the base of the flame. CHIMNEY, 7 inches long made from uniform glass tubing, 1 inch outside diameter and 0.03 t o 0.06 inch in thickness. A chimney holder maintains the chimney in a vertical position. SCALE, made of aluminum, 4 inches long and graduated in 0.1inch divisions, mounted at the side of the burner. It is adjusted so that the zero mark on the scale coincides with the top of the wick tube. WICKTUBE,round, 0.25 inch in diameter. WICK,American Pett, 0.25 inch in diameter. ASSEMBLY. The lamp is placed on the base of a regular ring stand, on the vertical rod of which is mounted a ring which moves freely in a horizontal position and is actuated by means of a control rod. The ring supports a 3-inch flat-bottomed porcelain dish filled with cracked ice for detecting the smoke point. Both the control rod for the ring and the milled operating wheel to adjust the flame height are extended through the right side of a ventilated cabinet fitted with a glass front door. This enables the lamp t o be operated in a draft-free space, and allows operating controls t o be manipulated from without. Procedure The oil to be tested is placed in the fount and filled within 0.5 inch from the top. A piece of wick approximately 4 inches long is cut, placed in the burner, and burned so that the tip is rounded on the top and no rough edges remain. The burner and wick assembly is then placed in the fount, and the chimney set in place, care being taken that the flame is burning centrally within the chimney. The porcelain dish with a clean undersurface is filled with cracked ice and placed in the holder. The lam is lighted, the wick being adjusted t o give a small flame for atout 15 minutes, and the door of the cabinet being left open to permit the flame to stabilize itself. The zero mark on the scale is adjusted to coincide with the burner top. The cabinet door is then closed and the flame turned up slowly t o a height where a smoke spot is formed on the bottom of the dish. The dish is then moved away from the chimney and the flame turned down one-half of one scale division. This procedure is continued until the maximum height of the flame is produced without a smoke spot forming on the dish. The final adjustment of the flame is made with an accuracy of one-half of one scale division, or 0.05 inch. This maximum height of the flame is read directly by means of the aluminum scale, and represents the quality of the oil with regard to smoke tendency.
A very highly refined kerosene will give a flame height of 3.00 inches or more, a well refined stock about 2.00 inches, and an inferior grade less than 1.00 inch.
Increasing the degree of refinement of a keorsene results in an increase in flame height, so that the factor lamp test is a valuable index to the refiner for control of the refining process. I n the sulfuric acid treatment of kerosene distillate, the amount of acid used in dumps may a t any stage of the treatment be correlated with this lamp test. Furthermore, for kerosene distillate from a known crude source, the amount of acid required to produce a given factor lamp test may be predicted.
FIGURE 2.
IMPROVED
FACTOR LAMP
The factor lamp is not designed to give an index of quality for which other lamps, such as the Saybolt standard, the A. R. A. signal semaphore, and Rayo, are more suitable and are now widely used in the industry. Two different kerosenes having the same factor lamp test may be graded differently for quality in another lamp, and vice versa. This will be true for other types of smoke-tendency test lamps. Therefore, when a given grade of kerosene is required to meet a smoketendency test, the oil should be tested in a lamp such as the factor lamp, which is designed for this specific purpose.
Summary A method for the determination of the smoke tendency of refined kerosene is described, by means of which this specific property is evaluated. The actual smoke point is detected with great accuracy, using an ice-cold dish, the flame height a t this point being measured directly on the scale. The time required for a test is about 20 minutes, the results being reproducible within 0.05-inch flame height, and for very highly refined stocks within 0.10-inch flame height.
Acknowledgment Acknowledgment is hereby made of the work done by M. H. Lipp and P. D. Cookson of the Standard Oil Company
JULY 15, 1936
ANALYTICAL EDITION
Laboratories, Richmond, Calif., in developing improvements in this method which has been used very effectively by this company for several years as a routine test.
Literature Cited (1) Bowman, S., J . Inst. Petroleum Tech., 13, 410 (1927). (2) Inst. Petroleum Tech., “Standard Methods of Testing Petroleum and Its Products,” 3rd ed., London, 1935. (3) Jackson, J. S., World Petroleum Congr., London, 1933, Proc., 2, 699-702 (Preprint 58).
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(4)Kewley, J., and Jackson, J. S.,J . Inst. Petroleum Tech., 13, 364 (1927). (5) Minchin, S. T., Ibid., 17, 102 (1931). (6) Minchin, S. T., World Petroleuni Congr., London, 1933, Proc., 2, 738-43 (Preprint 66). (7) Thomas, W. H., J . Inst. Petroleum Tech., 13, 402 (1927). (8) Woodrow, W. A., Ibid., 13, 398 (1927). (9) Woodrowo w. A.7 World Petroleum Congr.9 London, 193%P T O C . , 2, 732-3 (Preprint 67). RECEIVED December 23, 1935.
Extending the Useful Range of Concentric Cylinder Viscometers LOMBARD SQUIRES AND R. L. DOCKENDORFF Massachusetts Institute of Technology, Cambridge, Mass.
By means of a friction factor-Reynolds where dl and dz are the diameT H E convenience of the connumber plot it has been found possible to ters of the inner and outer cylincentric cylinder type of viscometer for technical work is determine the viscosity of liquids in a conder, respectively, and L is the well recognized. Such instrulength of the cylinder over which centric cy1inder ments as the Stormer, Couette, even when the the viscous drag is being measor MacMichael viscometer comliquids are so fluid that their motion is turured. bulent during the determination. While At large values of R, the mobine ease and rapidity of maniputhe method becomes more inaccurate as tion of the liquid changes from lation with considerable flexibility and are accurate enough turbulence increases, satisfactory results viscous bulent flow, stream-line and inflow thistolatter turfor many types of industrial problems. However, the applican be Obtained with instruments such as region T is no longer proporcation of all these instruments, the Stormer or MacMichael viscometer for tional to R. It is, therefore, no longer justifiable to calculate liquids as fluid as water. p a r t i c u l a r l y t h e Stormer, is the viscosity by Equation 1. limited to liquids whose viscosiFurthermore, the value of R at ties are above 0.5 to 1.0 poisewhich the motion of the liquid becomes turbulent is directly i. e., to liquids from 50 to 100 times the viscosity of water. In proportional to the viscosity and for liquids of low viscosity consequence, one is forced to use other methods for a great will be small. To keep within the viscous region for these many liquids and solutions of moderate viscosities. liquids, R must be kept so small that all precision is lost. This serious limitation is a consequence of the method As an illustration, consider the data of Figure 1, obtained employed in calculating the viscosity from the data. If the in a Stormer viscometer, in which the torque is proportional motion of the liquid is viscous, it can be easily shown that to the actuating weight driving the rotating cylinder. With p = kT/R (1) a heavy mineral oil ( p = 0.70 poise), the majority of the points lie on a straight line through the origin and are therefore where T is the torque acting on one of the cylinders, R is on the viscous range. The upper end of the line shows the angular velocity of the rotating cylinder, and k is a conpronounced curvature and indicates that turbulence has been stant of the instrument. If the cylinders are concentric, developed. For this oil, then, an actuating weight of less uniform, and sufficiently long for end effects to be neglected, than 100 grams should be used if Equation 1 is to be valid. With a light oil ( p = 0.0454 poise), even with the smallest weight considerable curvature is evident, indicating that the viscosity of this liquid cannot be calculated in the conventional way by the use of Equation 1. The problem of finding the viscosity of a liquid from measurements in the turbulent region may be solved in the following way: From the hydrodynamics of the situation, it is obvious that R is a unique function of the density and viscosity of the liquid, the dimensions of the instrument, and the value of the torque, T. a Define f, the friction factor, as
* Di
From the analogy with fluid flow in pipes, f is a function of the quantity, Re,which may be termed the Reynolds number, defined as T. IN GRAMS
