Microdetermination of Flash Point on Petroleum Products PHILIP McCUTCHAN AND D. A. YOUNG Research and Process Department, Union Oil Co. of California, Brea, Calif. The need arose for the determination of the flash point on very small quantities of petroleum products, and suitable methods could not be found in the literature. The procedure and equipment, as developed, allow the observation of a visible flash from 0.3 ml. of sample heated in a flash chamber drilled into an aluminum block. The precision is excellent and the apparatus is simple to construct and operate. The values obtained are the same as from the Cleveland open cup procedure, ASTM D 92-46, which requires approximately70 ml. of sample. This correlation enables one to obtain flash points on the small quantities of products frequently encountered in research investigations.
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H E development of micromethods for the determination of physicochemical measurements of oils is made desirable by the limited amounts of sample often available during research on petroleum products. Some of the micromethods that have been reported in the literature are: the determination of viscosity of oils by Levin ( 5 ) and by Cannon (3), and the determination of pour point, titer, and vapor pressure by Levin, Morrison, and Reed (6).
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SPARK
Figure 1. Micro Flash Block
One of the important properties of fuels and lubricants is the temperature a t which the material flashes n-hen it is exposed to a spark or flame. It is believed that a method for the determination of flash points on a micro scale vould be of considerable value. A number of methods have been proposed for flash point determination that use less material than required by ASTM methods. Osmond and Abrams (9) devised a flash adapter that makes possible the use of 20-ml. samples in the Cleveland open cup and Able cup methods. Ettele ( 4 ) described an apparatus consisting of a grooved bar, heated a t one end, in which the oil TTas placed and tested for flash point a t various positions along the bar. Ormandy and Craven ( 7 ) determined flash points with 7 ml. of material in a test tube. An inverted bell was inserted in the test tube and an electric spark passed over the sample at frequent temperature intervals. These same n-orkers (8) later devised another method for flash points in which 10 ml. of sample wa8 tested a t various pressures in a sealed chamber connected to a manometer. Ignition was by electric spark and the flash was detected by a surge in the manometer.
As no method was found in the literature for flash point determinations on a micro scale, the development of such a method was undertaken. I n considering the problem it &-as believed that the follon-ing conditions must be satisfied in order to obtain correct results: 1. The rate of temperature increase must be controlled 2. The accumulation of a flammable amount of vapor must be ensured by a controlled air circulation 3. To produce a distinct flash, the ignition must be made by an electric spark
Two different approaches to this problem have been follon-ed in this laboratory. The problem was first investigated by combining and modifying the procedures of Ormandy and Craven ( 7 , 8). Although satisfactory results were obtained, this method was abandoned in favor of the simpler apparatus described below, which gave excellent results. I n the second method of investigation, the flash point was detected visually. The sample m-as placed in a chamber in an aluminum block that was heated a t a controlled rate by a microburner. Heating by electrical means is no doubt possible, but was not tried because of the simplicity and ease of control afforded by the gas burner. The vapors were ignited by a spark directed against the side of the chamber. It was soon found that reproducible values could be obtained, but that the temperature a t which a given flash point was observed mas dependent on the size of the sample chamber and the circulation of air. These variables were balanced to give the Cleveland open cup ( 1 ) values on a micro scale. Preliminary data indicated that modifications of the apparatus may allow correlation with Pensky-Martens closed tester (2) values. As yet, however, concordant results have not been obtained n-ith all types of samples. APPARATUS
The design of the apparatus is shown in Figure 1. I t consists of a cylindrical aluminum block, 1, of 2-inch diameter and 2.5inch length, containing a flash chamber, 2 1 / 6 4 inch in diameter, 2, drilled to a depth of 1.875 inches with the bottom finished off flat. A 2-inch thermometer well, 3, is drilled close to the flash chamber. A slanted observation port, 4, of 11/32-inchdiameter, is drilled a t a 70" angle, centered l * l / c a inches from the top of t h e block, which mill enter the flash chamber just above the surface of the sample. A horizontal 9/64-inch hole, 5, centered 1/32 inch from the bottom of the flash chamber, is drilled for insertion of the ignitor. The ignitor, 6, consists of a platinum wire sealed into a 3-mm. glass tubing. Aiproper position of the arcing point of the ignitor is assured by a flange, 7 , on the tubing. The ignitor rests in the hole with the flange against the block as shown in Figure 1. Failure to insert the ignitor to the proper depth causeel confusing reflections, and the incorrect position of the spark produces erroneous results. The ignitor is removed from the block after each determination to facilitate cleaning. The tip, 8, of' the platinum wire should be bent donnward so as to cause t h e spark to pass to the wall of the chamber on the lower side of t h e 1974
V O L U M E 2 4 , NO. 12, D E C E M B E R 1 9 5 2 tubing. Current for the spark is conducted to the platinum wire from the secondary of a high voltage induction coil, 9, capable of furnishing a spark of a t least 1-millejoule energy. The block is supported by a clamp on a vertical rod that gives facility in adjusting the height of the block. This provides a flexibility in heat control that is needed for samples of widely different flash points. The flash chamber is closed by a cap, 10, bearing a center hole 11/64 inch in diameter and with the cap fitting into the top of the chamber so as to extend down 0.25 inch. Total thickness of the ~ cap is about 9 / inch. The induction coil and aluminum block assembly are mounted in a three-sided case fashioned from sheet metal (see Figure 2 for details of assembly and wiring). An ASTM open flash thermometer is used, graduated in Fahrenheit degrees, with the range from +20° to $760" F., and conforming t o the requirements for thermometer 11 F, as described in the standard specifications for ASTlZI thermometers. ii high frequency coil of the Tesla type is required. A high frequency coil sold by the Central Scientific Co. is satisfactory for adaptation t o the unit. The danger of electrical shock is eliminated bp connecting the primary of the induction coil through two push-button microswitches. The operator must use both hands to press these sxitches, and, therefore, cannot inadvertently contact the ignitor a-hile there is high voltage. The flash block must be grounded a t all times nhen in use. The sketch in Figure 2 shoa-s the general arrangement. PROCEDURE
Approximately 0.3 ml. of sample is introduced into the bottom of the flash chamber, and the cap is fitted into the top.
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1975 The sample may be conveniently added with a 1-ml. tuberculin eyringe. The syringe is used without the needle. The block is heated with a microburner a t about 30' F. per minute until around 100" F. below the expected flash point and then a t 10" F. per minute for a t least the last 50" F. -4spark should be made in the chamber a t each 5" F. starting a t about 30" F . below the flash point. EXPERIMEKT4L
I n establishing the necessary balance of variables to attain the desired result, it was observed that the degree of circulation of the convection current of air above the sample was a very significant variable. This circulation was controlled by the diameter of the hole drilled through the aeration cap. With no cap, flash xvas 20' F. high With a '6/64-inch hole, flash was 10" F. high With an 11/6a-inchhole finally adopted, flash was correct With cap closed, flash was 20" F. low The ratio of the air space in the chamber to the sample ivas also important. Decreasing the volume of the flash chamber by about one third lonwed the flash point about 15" F. The proper dimensions for duplication of Cleveland open cup values over the range from 200" to 500" F. were found to be an ignition spark a t about ' / 8 inch above the sample surface, a flash chamber of 3'/@-inch diameter and 17/s-inch depth, and an aeration cap bearing an ll/sa-inch hole with the cap fitted into and extending about 0.25 inch into the chamber.
1976 Table I.
ANALYTICAL CHEMISTRY Comparison of Cleveland Open Cup Flash Point with Micro Flash Point
Material Diesel receiver C
Cleveland Open Cup Flash Point ( I ) , F. Micro Flash Point, F. Operator A Operator B Operator B Operator C ... 205 205 20.5
Spray oil A
305
210 300
Spray oil B
325
320
205 305 305
2in
320
313
340 340
Spray oil C
340
Printing ink oil SAE 20 lubricating
360
345 340 360
320 315 345 343 360 360
410
430
420 4Ln
435
435
445
SAE 30 compounded oil
410 44.3
450
465
...
Neutral oil
475
470
4.55 4R0 460 470 470 450 49.5 480
Oil
SAE 30 lubricating 011
Mineral oil
500
450
... ...
... 450
475 480
...
RESULTS
Results have been obtained on samples covering a wide range of flash points with good duplicability throughout. For the range from 200" to 500' F., which is the range of normal interest for flash points by the Cleveland open cup, comparative results on 10 samples are shoyn in Table I. A large number of various types of oils have also been tested in the course of regular analytical xork with good duplicability of results. COR-CLUSION S
Apparatus has been designed and a method developed for
obtaining reproducible flash points on a micro scale (0.3-ml. sample). I n the range 200" to 500" F., the values are essentially the same as those obtained using the Cleveland open cup procedure described in ASTM method D 92-46. The micromethod, as compared to the macro, requires the same amount of time and gives equal precision, but uses only 0.3 nil. of sample instead of 50 to 70 ml. The stated specifications must be closely followed, for the flash point values are very dependent on the dimensions of the apparatus. The design of the apparatus permits determinations in the open laboratory, because a dark hood is not required and the rewlts are not affected by normal air currents. ACKNOWLEDGMENT
The authors wish to express appreciation t o the Gnion Oil Co. of Califoriiia for permission to publish these data. LITERATURE CITED
(1) Am. SOC.Testing Materials, "Standards on Petroleum Products and Lubricants," Designation D 92-46, September 1951. (2) Ibid., Designation D 93-46. ENQ.CHEM.,As.ir,. ED., (3) Cannon, M. R., and Fenske, M. R., IND. 10, 297 (1938). (4)Ettele, C., U. S.Patent 1,554,993 (Sept. 29, 1925). ( 5 ) Levin, Harry, IND.ESG. CHEM.,ANAL.ED.,9, 147 (1937). (6) Levin, Harry, Morrison, A. B., and Reed, C. R., ASAL. CHEM., 22,188-91 (1950). ( 7 ) Ormandy, W. R., and Craven, E. C., J . Inst. Petroleum Tc~~hnol., 8, 145-80 (1922). ( 8 ) Ibid., 9 , 39-45 (1923). (9) Osmond, C. H., and Abrams, V. R., dtlantic Lubricator, 4, S a . 6 (February1921).
RECEIVED for review June 17. 1552. Accepted August 18, 1552. Presented before the Division of Refining at the 17th Midyear Meeting of the American Petroleum Institute, San Francisco, Calif., May 12 to 13, 1552.
Colorimetric Estimation of Residual Benzene Hexachloride WENDELL F. PHILLIPS Beech-Nut Packing Co., Canajoharie, N . Y . The lack of a sufficiently specific and sensitive chemical method for the detection of microgram quantities of benzene hexachloride prompted the investigation which led to the development of this colorimetric method. When benzene hexachloride is refluxed with an excess of aniline, a mixture believed to consist of diphenylamine and dichlorodiphenylamines is formed. This mixture forms a violet color with an absorption maxima at 510 mp when oxidized with vanadium pentoxide in 5 0 q ~sulfuric acid. Beer's law is obeyed over the range of 2 to 120 micrograms of the gamma isomer. The method described is readily adapted to routine quality control analyses and should be useful to the food industry.
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I S C E Slade (8) announced the insecticidal activity of the gamma isomer of benzene hexachloride ( Ij2,3,4,5,6-hexachlorocyclohexane) it has become one of the major chemicals used in modern agriculture. The analytical methods ( 1 ) for determining this compound are not adequate for residue analysis, except for the recently described Schechter-Hornetein ( 7 ) method. The method proposed belon- is a modification of the procedure prrsented by Fairing ( 3 ) before the Division of Agricultural and Food Chemistry, a t the 119th meeting of the ~ ~ M E R I C ACHEMICAL X SOCIETY.
Among the published data on the chemistry of benzene hexachloride is a study reported in 1887 by Neunier ( 6 ) ,in which he noted a reaction betn-een aniline and benzene hexachloride. Subsequent investigation revealed that, when a large quantity of gamma-benzene hexachloride is refluxed with aniline and the
reaction products are separated, as indicated in the procedure, a mixture of compounds is obtained which forms a violet color (absorption maximum a t 555 mF) on oxidation in 50y0 sulfuric arid (v./v.) containing 0.05 mg. per ml. of vanadium pentoxide. The mixture is believed to contain three components n-hich form color n-hen treated n-ith vanadic acid. One of them is a dichlorodiphenylamine and the other tvio have not been satisfactorily identified, but they may be diphenylamine and another dichlorodiphenylamine. One of the unidentified compounds produces a red color in the vanadic acid solution which has an absorption maximum at 510 mp. The dichlorodiphenylamine forms a purple color which has an absorption maximum at 555 mp. K i t h the same reagent, diphenylamine gives a blue ( olor which has an absorption maximum a t 595 mp. When microgram quantities of gamma-benzene hexavhloride
