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Communications A Flash Point Value for n-Dodecane Based on the Manual Pensky-Martens Closed Cup Method (ASTM D-93) Janet M. Hughes Geo-Centers, Inc., Indian Head Highway, Ft. Washington, Maryland 20744
Dennis R. Hardy and Erna J. Beal* Naval Research Laboratory, Code 6181, 4555 Overlook Ave., Washington, D.C. 20375-5342 Received January 2, 1996. Revised Manuscript Received June 26, 1996 Flash point, as defined by ASTM D-93, is the “lowest temperature corrected to a barometric pressure of 101.3 kPa (760 mmHg), at which application of a test flame causes the vapor of a specimen to ignite under specified conditions of the test”.1 By this very definition the flash point of a substance is dependent upon the test method. There are many different methods used to determine the flash point of a liquid, such as Tag open2 and closed cup,3 Cleveland open cup,4 Setaflash closed cup,5 and manual Pensky-Martens closed cup.6 Each of these methods gives a different value for the flash point; therefore, it is imperative to state which method is used when citing a flash point value for a particular substance. The US Navy adopted the manual Pensky-Martens closed cup method (ASTM D-93) as the method of choice for ship board use in the 1970s. Today this method is being used by more than 20 different countries.7 New automated devices meant to simulate flash point values of the manual Pensky-Martens closed cup method are in production. A liquid which can be used as a calibration fluid for these types of devices is n-dodecane. For this reason it is important to know what the actual value for the flash point of n-dodecane is using the manual Pensky-Martens closed cup apparatus. The National Fire Protection Association (NFPA) published (1) ASTM Standard Test Methods for Flash Point by PenskyMartens Closed Tester. In Annual Book of ASTM Standards; ASTM: Philadelphia, 1993; Vol. 05.03; ASTM 93-90, p 29. (2) ASTM Standard Test Method for Flash Point and Fire Point of Liquids by Tag Open-Cup Apparatus. In Annual Book of ASTM Standards; ASTM: Philadelphia, 1993; Vol. 05.03, ASTM D1310-86. (3) ASTM Standard Test Method for Flash Point by Tag Closed Tester. In Annual Book of ASTM Standards; ASTM: Philadelphia, 1993; Vol. 05.03, ASTM D56-87. (4) ASTM Standard Test Method for Flash and Fire Points by Cleveland Open Cup. In Annual Book of ASTM Standards; ASTM: Philadelphia, 1993; Vol. 05.03, ASTM D92-90. (5) ASTM Standard Test Methods for Flash Point by Small Scale Closed Tester. In Annual Book of ASTM Standards; ASTM: Philadelphia, 1994; Vol. 05.02, ASTM D2828-93. (6) ASTM Standard Test Methods for Flash Point by PenskyMartens Closed Tester. In Annual Book of ASTM Standards; ASTM: Philadelphia, 1993; Vol. 05.03, ASTM D93-90. (7) Wray, H. A., Ed. Manual on Flash Point Standards and Their Uses. ASTM Manual Series MNL 9; ASTM Publication Code No. (PCN) 28-009092-31; ASTM: Philadelphia, 1992; pp 129-134.
Table 1. Experimental Average Values for the Flash Point of n-Dodecane Using the Manual Pensky-Martens Closed Cup Method n-dodecane
flash point (°C)
Phillips-66 (a) Phillips-66 (b) Humphrey Kodak average
85 85 86 87 86
Table 2. Three Independent Laboratories’ Experimental Average Values for the Flash Point of n-Dodecane Using the Manual Pensky-Martens Closed Cup Method laboratory
flash point (°C)
A B C average
86 85 85 85
flash point value for n-dodecane is 74 °C (165 °F).8 After a thorough review of the literature it was found that this value first appeared in NFPA 1934;9 however, there is no method cited. This is a value for n-dodecane that is widely used (in the MSDS for example) that cannot be certified as being run using a specific method. The purpose of this Communication is to provide a value for the flash point of n-dodecane using the manual PenskyMartens closed cup method (ASTM D-93). Four different samples of n-dodecane, two from Phillips-66 (99 mol % minimum), one from Humphrey (99.6%), and one sample from Kodak (99% minimum), were run in duplicate following ASTM D-93. The average values can be found in Table 1. The values obtained for the flash point of each n-dodecane sample were within the repeatability of the test (2 °C). Table 2 shows the results of three independent measurements done in different countries. These are averages of multiple experiments and are well within the reproducibility of the test method (3.5 °C). Using ASTM D-93, the Manual Pensky-Martens Closed Cup Method, the flash point for n-dodecane is 85 °C (185 °F). (8) Fire Protection Guide to Hazardous Materials, 11th ed.; NFPA: Boston, 1994; pp 325-45. (9) Fire Hazard Properties of Certain Flammable Liquids, Gases and Volatile Solids; NFPA: Boston, 1934; NFPA No 325-P-1934, p 21.
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A recent study by API/NIST determined ASTM D-93 manual and automated Pensky-Martens closed cup values for n-decane (53 °C), n-undecane (69 °C), ntetradecane (109 °C), and n-hexadecane (133 °C).10 Graphical interpolation of these nonlinear values gives a value for n-dodecane of 83 °C which compares favorably with the experimentally determined values reported here. It is worth noting that pre-1966 literature values for n-dodecane cited by Affens11 are considerably lower. The average experimental value that he reported
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for n-dodecane was 74 °C (cf. refs 8 and 9). These pre1966 literature values agreed well with values that he independently determined both graphically and by calculation for n-dodecane (76 °C). These flash point calculations were based upon carbon number, vapor pressure, and lower concentration limit of flammability only. The basis for the discrepancy in experimentally determined flash point values over a 30 year period for n-dodecane and a variety of n-alkanes is under investigation by this laboratory. EF960002Y
(10) ASTM Minutes of S-15 Coordinating Committee on Flash Point Meeting, April 19, 1995, Washington, DC.
(11) Affens, W. A. J. Chem. Eng. Data 1996, 11, 197-202.
