A CATALOGUE OF CRUDE OIL AND OIL PRODUCT PROPERTIES

by 

P. Jokuty 1, S. Whiticar 2, Z. Wang 1, M. Fingas 1, 
P. Lambert 1, B. Fieldhouse 1, and J. Mullin 3 

1 Emergencies Science Division, Environment Canada, Ottawa, Ontario 
2 Whiticar Scientific, Ottawa, Ontario 
3 United States Minerals Management Service, Department of the Interior, Herndon, Virginia 


This report has not undergone detailed technical review by the Environmental Protection Directorate and the content does not necessarily reflect the views and policies of Environment Canada. Mention of trade names or commercial products does not constitute endorsement for use. This unedited version is undergoing a limited distribution to transfer the information to people working in related areas. This distribution is not intended to signify publication and, if the report is referenced, it should be cited as a manuscript report of the Directorate indicated below. Any comments concerning its content should be directed to: 

Environment Canada

Environmental Technology Advancement Directorate
Emergencies Science Division
Environmental Technology Centre
Ottawa, Ontario 
K1A 0H3 

ABSTRACT 

This catalogue provides data on various physical-chemical properties of crude oils and petroleum products. The properties that are reported are those which will likely determine the environmental behaviour and effects of spilled oil. The oils are arranged in alphabetical order. 

ACKNOWLEDGEMENTS 

This project was co-funded by the United States Minerals Management Service and the Emergencies Science Division of Environment Canada. The authors thank all those who supplied samples and technical data. 

TABLE OF CONTENTS

List of Oils (Alphabetical by Oil Name)

Introduction
Description of Tests and Methods

API Gravity
Water Content
Evaporation Equation(s)
Flash Point
Fire Point
Flammability Limits of Vapour in Air
Ignition Temperature
Reid Vapour Pressure
Hydrogen Sulphide
Odour Threshold
Density
Pour Point
Viscosity
Dynamic Viscosity
Kinematic Viscosity
Saybolt Viscosity
Emulsions
Emulsion Formation
Emulsion Viscosity/Emulsion Water Content
Chemical Dispersibility
Hydrocarbon Groups
Adhesion
Volatile Organic Compounds
GC Analysis
Surface Tension and Interfacial Tension
Boiling Point Distributions
Metal Content
Sulphur 
Aqueous Solubility 
Toxicity
Biological Oxygen Demand (BOD)
References

INTRODUCTION 

During any oil spill incident, the properties of the spilled oil must be known immediately. Unfortunately, the properties routinely measured by oil producers and refiners are not the ones that on-scene commanders need to know most urgently. Oil producers and refiners typically do not know to what extent their oils will evaporate and how quickly; to what extent dispersibility will occur naturally, or be enhanced with dispersants; whether emulsions will form; if the oil is likely to sink or submerge; the viscosity of the oil, at ambient temperatures, as it evaporates; the health hazard to on-site personnel from volatile organic compounds; and the toxicity to marine or aquatic organisms. 

The Emergencies Science Division (ESD), also known as the Environmental Emergencies Technology Division (EETD) prior to 1990, of Environment Canada, (the Canadian counterpart of the U.S. Environmental Protection Agency), is an organization that has been dedicated to performing oil and chemical spill research since 1973. Since 1984, Environment Canada has been analyzing crude oils and oil products to determine not only basic physical properties, but also how oil behaves when spilled in the environment. A catalogue of oil properties, containing both data produced in-house and data from other sources, was first prepared by Environment Canada in 1984. Subsequent updates were produced in 1986, 1988, 1989, 1990, and 1992. A Catalogue of Crude Oil and Oil Product Properties has been so popular that interagency committees have requested that data collection for, and updating of the catalogue, be an ongoing operation. This work has been continuously co-funded by the U.S. Minerals Management Service since 1989. The oil properties database presently contains information on over 350 different oils. 

For each oil in the catalogue, the properties listed are those that indicate a spilled oil's environmental behaviour and effects. Where available, data is included for both fresh and evaporated oils. Environment Canada is the largest single source of data for the oil catalogue. Whenever possible, Environment Canada has used standard test methods, such as those of the American Society for Testing and Materials (ASTM). In addition, many oil analytical methods have been developed by ESD specifically for determining the environmentally significant properties and behaviours that oil producers and refiners do not measure. These include methods for emulsion formation and characterization, measuring chemical dispersibility, determining specific and generalized evaporation equations for oils, measuring volatile organic compounds, and determining acute aquatic toxicity. Because evaporative loss results in significant changes in the physical properties and chemical composition of spilled oils, which in turn influence choices made relating to oil spill countermeasures, ESD measures most properties not only for fresh oils, but also for evaporated oils prepared in the laboratory to represent various degrees of evaporation (see the Appendix of Methods, Bulk Evaporation of Oils). The information collected is maintained in an electronic database and also used to produce, at intervals, A Catalogue of Crude Oil and Oil Product Properties. 

Most of the oil analytical methods used by ESD are described in the Appendix of Methods. Some ESD methods have been previously described in detail in the literature and the reader is referred to these sources to avoid unnecessary repetition. 

Since data from many other sources are also included in the catalogue, differences in reported values may be due to the variance of samples and inherent differences in measurement techniques. The reader who wishes to make use of such data should refer directly to the original source to obtain specific details on the techniques and parameters used. 

The crude oils and oil products are arranged in alphabetical order. Oil products are listed according to their most commonly used names. All synonyms are cross referenced in the Table of Contents. In addition to a complete alphabetical listing, a listing by geographic origin has also been included. The names used to identify the oils in this catalogue are those used by the authors of the original data or by the suppliers of the samples. Common synonyms are included where appropriate. 

The reader should be aware of the following points when searching for information on a specific oil. Crude oils from the same region are often given the same name even though oils from different wells can have markedly different properties. Oils that are transported are often blends of different crude oils, and the relative proportions of component oils frequently change. Therefore, the physical and chemical properties will vary. Similarly, the properties of oil taken from an individual well can vary with the depth of the well and the year of production. Also, different authors may refer to the same crude oil by different names, or to different crude oils by the same name. 

DESCRIPTION OF TESTS AND METHODS 

API Gravity

See Density. 

Water Content

Some of the oils analyzed by ESD contain substantial amounts of water. Because any process that would separate the oil and water would also change the composition of the oil, most properties were determined on the oils as received. Exceptions are noted in the individual data tables. Therefore, for those oils with significant water contents, (>5%), many of the properties measured do not represent the properties of the "dry" oil.

At ESD, water contents were determined by Karl Fischer titration using a Metrohm 701 KF Automatic Titrator. A slightly modified version of ASTM method D 4377 was used (ASTM, 1996a). For more details, see the Appendix of Methods. 

Evaporation Equation(s) 

Evaporation is a major process which contributes to the weathering of spilled oil. While pure compounds evaporate at constant rates, oils, which are composed of thousands of compounds, do not. Rapid initial loss of the more volatile fractions is followed by progressively slower loss of less volatile components. It is not uncommon for 25% of the total volume of an oil spill to evaporate within one day of the spill (Fingas et al., 1979). 

Using a simple pan evaporation technique, evaporation rate equations have been developed for approximately 60 oils. For more details, see the Appendix of Methods, Pan Evaporation of Oils. 

Flash Point 

The flash point of a fuel is the temperature to which the fuel must be heated to produce a vapour/air mixture above the liquid fuel that is ignitable when exposed to an open flame under specified test conditions. In North America, flash point is used as an index of fire hazard. As such, shipping regulations use flash point as a criterion to establish labelling requirements. 

Flash point is an extremely important factor in relation to the safety of spill cleanup operations. Gasolines and other light fuels can be ignited under most ambient conditions and therefore pose a serious hazard when spilled. Many freshly spilled crude oils also have low flash points until the lighter components have evaporated or dispersed. 

There are several ASTM methods for measuring flash points. Methods D 93/IP 34 - Standard Test Methods for Flash Point by Pensky-Martens Closed Tester and D 56 - Standard Test Method for Flash Point by Tag Closed Tester are among the most commonly used (ASTM, 1996a). The Pensky-Martens tester has an integral stirrer, but no cooling bath. The minimum flash point that can be determined by method D93/IP34 is 10 'C. The Tag closed tester has an integral cooling bath, but no stirring mechanism. Method D 56 is intended for liquids with a viscosity less than 9.5 cSt at 25 'C. The flash points and fire points (see below) of lubricating oils can be determined by ASTM method D 92/IP 36 - Standard Test Method for Flash and Fire Points by Cleveland Open Cup (ASTM, 1996a). 

Many fresh crude oils have flash points below 10 /C and/or viscosities above 9.5 cSt at 25 'C. For this reason, at ESD a SUR BERLIN TAG 2 automatic flash point tester, which has been modified by adding a stirring mechanism, is used to determine flash points. The mechanism operates in a similar fashion to a Pensky-Martens tester, but is of a more efficient design. The stirrer aids in producing more uniform heat transfer to oils that exceed the design viscosity, and in no way interferes with the test mechanism. Flash points measured by this instrument are generally repeatable to +/- 4 'C. For more details, see the Appendix of Methods. 

In the data section, flash points taken from the literature, and determined by open-cup or closed-cup testers are designated by '(O.C.)' and '(C.C.)', respectively. No designation is provided if the testing method is not known. 

Fire Point 

Fire point is the lowest temperature, corrected to one atmosphere pressure (101.3 kPa), at which the application of a test flame to the oil sample surface causes the vapour of the oil to ignite and burn for at least five seconds. For ordinary commercial lubricating oils, the fire point usually runs about 30 /C above the flash point (Esso Petroleum Canada, 1990). The flash points (see above) and fire points of lubricating oils can be determined by ASTM method D 92/IP 36 - Standard Test Method for Flash and Fire Points by Cleveland Open Cup (ASTM, 1996a). 

Flammability Limits of Vapour in Air 

The percent concentration in air (by volume) is given for the lower and upper limit. These values give an indication of relative flammability. The limits are sometimes referred to as "lower explosive limit" (LEL) and "upper explosive limit" (UEL). 

Ignition Temperature

Sometimes called "autoignition temperature", this is the minimum temperature at which the material will ignite without a spark or flame being present. The method of measurement is given in ASTM method E 659 - Standard Test Method for Autoignition Temperature of Liquid Chemicals (ASTM, 1996b). 

Reid Vapour Pressure 

Vapour pressure is an important physical property of volatile liquids. It is the pressure that a vapour exerts on its surroundings. Its units are kilopascals, corrected to one atmosphere (101.3 kPa). For volatile petroleum products, vapour pressure is used as an indirect measure of evaporation rate. Vapour pressure can be measured by a variety of methods including Reid, dynamic, static, isoteniscopic, vapour pressure balance, and gas saturation. The most commonly used method for crude oils has been the Reid vapour pressure, as determined by ASTM method D 323 - Standard Test Method for Vapor Pressure of Petroleum Products (Reid Method), (ASTM, 1996a). This test method determines vapour pressure at 37.8 'C (100 'F) of petroleum products and crude oils with initial boiling point above 0 'C (32 'F). It is measured by saturating a known volume of oil in an air chamber of known volume and measuring the equilibrium pressure which is then corrected to one atmosphere (101.3 kPa). 

Hydrogen Sulphide

Unlike other sulphur compounds in crude oils, which tend to accumulate in the distillation residue, hydrogen sulphide is evolved during distillation or other heating processes. During an oil spill, this makes it a safety concern, as hydrogen sulphide is a toxic gas with a time-weighted average (TWA) exposure limit of 10 ppm and a short-term exposure limit (STEL) of 15 ppm (ACGIH, 1996). 

Odour Threshold

This is the lowest concentration in air that most humans can detect by smell. The value cannot be relied on to prevent overexposure because human sensitivity to odours varies over wide limits, some chemicals cannot be smelled at toxic concentrations, odours can be masked by other odours, and some compounds rapidly deaden the sense of smell (CHRIS, 1991). 

Density 

Density is defined as the mass per unit volume of a substance. It is most often reported for oils in units of g/mL or g/cm3, and less often in units of kg/m3. Density is temperature-dependent. The figure below shows how the density of water changes with both salinity and temperature. Oil will float on water if the density of the oil is less than that of the water. 


This will be true of all fresh crude oils, and most fuel oils, for both salt and fresh water. Bitumens and certain residual fuel oils may have densities greater than 1.0 g/mL and their buoyancy behaviour will vary depending on the salinity and temperature of the water. The density of spilled oil will also increase with time, as the more volatile (and less dense) components are lost. After considerable evaporation, the density of some crude oils may increase enough for the oils to sink below the water surface. 

Two density-related properties of oils are often used: specific gravity and American Petroleum Institute (API) gravity. Specific gravity (or relative density) is the ratio, at a specified temperature, of the oil density to the density of pure water. 

The API gravity scale arbitrarily assigns an API gravity of 10/ to pure water. API gravity is calculated as: 

Oils with low densities, and hence low specific gravities, have high API gravities. The price of a crude oil is usually based on its API gravity, with high gravity oils commanding higher prices. API gravity, and density or specific gravity at 15 /C, can be interconverted using Petroleum Measurement Table 3 (American Petroleum Institute, 1982). 

At ESD, density is measured using an Anton Parr DMA 48 digital density meter, and following ASTM method D 5002 - Density and Relative Density of Crude Oils by Digital Density Analyzer (ASTM, 1996a). In this way, densities can be measured to 0.0001 g/mL with a repeatability of "0.0005 g/mL. For more details, see the Appendix of Methods. 

Pour Point 

The pour point of an oil is the lowest temperature at which the oil will just flow, under standard test conditions. The failure to flow at the pour point is usually attributed to the separation of waxes from the oil, but can also be due to the effect of viscosity in the case of very viscous oils. Also, particularly in the case of residual fuel oils, pour points may be influenced by the thermal history of the sample, that is, the degree and duration of heating and cooling to which the sample has been exposed. 

From a spill response point of view, it must be emphasized that the tendency of the oil to flow will be influenced by the size and shape of the container, the head of the oil, and the physical structure of the solidified oil. The pour point of the oils is therefore an indication, and not an exact measure, of the temperature at which flow ceases (Dyroff, 1993). 

ESD uses a modified version of ASTM method D 97 - Standard Test Method for Pour Point of Petroleum Oils (ASTM, 1996a) for pour point determinations. For more details, see the Appendix of Methods. 

Viscosity

Dynamic Viscosity 

Viscosity is a measure of a fluid's resistance to flow; the lower the viscosity of a fluid, the more easily it flows. Like density, viscosity is affected by temperature. As temperature decreases, viscosity increases. The SI unit of dynamic viscosity is the millipascal-second (mPa.s). This is equivalent to the former unit of centipoise (cP). 


Viscosity is a very important property of oils because it affects the rate at which spilled oil will spread, the degree to which it will penetrate shoreline substrates, and the selection of mechanical spill countermeasures equipment. 

Viscosity measurements may be absolute or relative (sometimes called 'apparent'). Absolute viscosities are those measured by a standard method, with the results traceable to fundamental units. "Absolute viscosities are distinguished from relative measurements made with instruments that measure viscous drag in a fluid, without known and/or uniform applied shear rates." (Schramm, 1992). An important benefit of absolute viscometry is that the test results are independent of the particular type or make of viscometer used. Absolute viscosity data can be compared easily between laboratories worldwide. 

Modern rotational viscometers are capable of making absolute viscosity measurements for both Newtonian and non-Newtonian fluids at a variety of well controlled, known, and/or uniform shear rates. Unfortunately, no ASTM standard method exists that makes use of these viscometers. Nonetheless, these instruments are in widespread use in many industries. 

Prior to 1989, the dynamic viscosity results reported by EETD were measured using a Brookfield LVT viscometer. For non-Newtonian oils, the viscosity measurements were usually performed at shear rates of 1/s and 10/s. Dynamic viscosity data referenced as 'EETD 89' or 'ESD xx' were determined using a HAAKE RV20 Rotovisco with the M5 measuring system, SV1 and NV sensors, and HAAKE RC20 Rheocontroller. The Rheocontroller, which is connected to a personal computer, allows the shear rates to be controlled with great accuracy and precision. A dedicated software package performs automatic dynamic viscosity measurements and outputs the stored data in table and graphical formats. In general, the viscosity values obtained using this system will be repeatable to +/-5% of the mean. For more details, see the Appendix of Methods. 

Kinematic Viscosity

There are several ASTM Standard Methods for measuring the viscosity of oils. Of these, only methods D 445 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (the Calculation of Dynamic Viscosity) and D 4486 - Standard Test Method for Kinematic Viscosity of Volatile and Reactive Liquids, will yield absolute viscosity measurements (ASTM, 1996a). Both of these methods make use of glass capillary kinematic viscometers and will produce absolute measurements in units of centistokes (cSt) only for oils that exhibit Newtonian flow behaviour (viscosity independent of the rate of shear). 


The kinematic viscosity results reported by EETD were measured using Zeitfuchs cross-arm capillary viscometers and following ASTM method D 445. 

Saybolt Viscosity 

Although now obsolete, at one time the petroleum industry relied on measuring kinematic viscosity with the Saybolt viscometer and expressing kinematic viscosity in Saybolt Universal Seconds (SUS) or Saybolt Furol Seconds (SFS). Occasionally, Saybolt viscosities are still reported in the literature. ASTM practice D 2161 - Standard Practice for Conversion of Kinematic Viscosity to Saybolt Universal Viscosity or to Saybolt Furol Viscosity (ASTM, 1996a) establishes the official equations relating SUS and SFS to the SI kinematic viscosity units, mm2/s. 

Emulsions

A water-in-oil emulsion is a stable dispersion of small droplets of water in oil. When formed from crude oils spilled at sea, these emulsions can have very different characteristics from their parent crude oils. This has important implications for the fate and behaviour of the oil and its subsequent cleanup. It is desirable, therefore, to determine if an oil is likely to form an emulsion, and if so, whether that emulsion is stable, and what its physical characteristics are. 

Emulsion Formation

At ESD, prior to 1994, the tendency for a crude oil to form a water-in-oil emulsion was measured using a method based on the rotating flask apparatus of Mackay and Zagorski (1982). All numerical values (mostly ones or zeroes) based on this method have subsequently been reduced to 'yes' or 'no', respectively, and indicate the formation (or not) of an emulsion that remained stable 24 hours after settling. 

In 1994, a new method was developed for the formation of water-in-oil emulsions. This method uses commercially available equipment. The apparatus uses the same end-over-end type of rotation as used by Mackay and Zagorski (1982), but the reproducibility is considerably improved. The water-to-oil ratio, the fill volume, and the orientation of the vessels were found to be important parameters affecting emulsion formation. For more details, see the Appendix of Methods. Again, emulsion formation tendency is reported as 'yes' or 'no'. Again, 'yes' indicates that the emulsion remains stable after a period of at least 24 hours. The term 'stability' implies a significant persistence of structure over time. After examining the influence of many factors, it was found that water content and emulsion viscosity are the two properties that can best be used to define emulsion stability. Emulsions that had decreases of less than 5% in water content, concurrent with viscosity increases to values greater than 100,000 cP, were stable. 

Emulsion Viscosity/Emulsion Water Content 

These properties are measured in substantially the same way as for oils. For more details, see the Appendix of Methods. 

Chemical Dispersibility 

In some oil spill situations and under appropriate conditions, dispersants may be an effective countermeasure for minimizing contamination of shorelines, or birds and mammals. 

The Swirling Flask Test (SFT) was developed for determining the effectiveness of various dispersants with different oils. Oil and dispersant are pre-mixed in a ratio of 25:1 and applied to salt water (3.3%) in a ratio of 1:1200. Prior to 1994 quantitation was done by ultraviolet/visible spectrometry of solvent extracts of the dispersed oil. Details of the apparatus and procedures used are given in the literature (Fingas et al., 1989a). Studies have also been done to determine the effects of oil-to-water ratios and settling times (Fingas et al., 1989b) and energy (Fingas et al., 1991; Fingas et al.,1992; Fingas et al., 1993). In 1994 the SFT was modified to use quantitation by gas chromatograph with flame ionization detection (GC/FID) (Fingas et al., 1995b). 

Hydrocarbon Groups 

The behaviour of crude oils at sea is dominated by their chemistry. The main constituents of crude oils can be grouped into several broad classes of compounds: saturates (including waxes), aromatics, resins, and asphaltenes. 

Saturates are alkanes with structures of CnH2n+2 (aliphatics) or CnH2n in the case of cyclic saturates (alicyclics). Small saturates (<C18) are the most dispersible components of oils. Large saturates (waxes) can produce anomalous evaporation, dispersion, emulsification, and flow behaviours. 

Aromatics are compounds that have at least one benzene ring as part of their chemical structure. The small aromatics (one and two rings) are fairly soluble in water, but also evaporate rapidly from spilled crude oil. Larger aromatics show neither of these behaviours to any extent. 

Resins and asphaltenes are similar in many ways. Asphaltenes can be thought of as large resins. Both groups are thought to be composed of condensed aromatic nuclei which may carry alkyl and alicyclic systems containing heteroatoms such as nitrogen, sulphur, and oxygen. Metals such as nickel, vanadium, and iron are also associated with asphaltenes. Both groups do not appreciably evaporate, disperse or degrade, and both groups stabilize water-in-oil emulsions when they are present in quantities greater than 3% (Fingas, 1994). 

Waxes are predominantly straight-chain saturates with melting points above 20 oC. 

The preceding definitions may be overly simplistic given the complex chemical composition of petroleum. A greater appreciation of oil chemistry and of how petroleum can be chemically fractionated can be obtained from more detailed texts such as the one by Speight (Speight, 1991). 

Saturate, aromatic, and polar contents can be determined using various techniques such as open column chromatography, high pressure liquid chromatography (HPLC), or thin layer chromatography with flame ionization detection (TLC/FID; also known by the trade name Iatroscan). TLC/FID is usually restricted to determinations on weathered oils, as significant losses of low boiling component are likely with fresh oils. It should be noted that each technique will likely yield different results. 

Prior to 1989, EETD used hexane for the precipitation of asphaltenes. Since then, ESD has used n-pentane as the precipitation medium. Since 1994, at ESD hydrocarbon groups in fresh and evaporated crude oils have been determined by using a combination of old and new methods. Asphaltenes are precipitated from n-pentane. Waxes can then be precipitated from a mixture of methyl ethyl ketone and dichloromethane at -32oC. To separate saturates, aromatics, and resins, deasphaltened oil (maltenes) is placed on an open silica column, and eluted sequentially with solvents of increasing polarity. For more details, see the Appendix of Methods. If the oil used has an initial boiling point (IBP) above 250 oC (determined by simulated distillation), a good mass balance can be obtained (>95%). However, most fresh crude oils will have an IBP well below 250 oC, and the loss of light ends during solvent recovery results in a poor mass balance. Fortunately, by making the reasonable assumptions that a) resin and asphaltene contents are not affected by evaporative losses, and b) the aromatic portion of the lost light ends can be equated to the BTEX plus C3-benzenes content (see Volatile Organic Compounds), it is possible to calculate the distribution of hydrocarbon groups. 

Adhesion

It has long been recognized that different oils tend to adhere to surfaces to a greater or lesser degree. A test was developed, using a standard surface, that gives a semi-quantitative measure of this adhesive property. 

For the purposes of this test, oil adhesion is defined as the mass of oil per unit area that will remain on a standard test surface, after 'dunking and draining' for 30 minutes, under prescribed conditions. For more details, see the Appendix of Methods. The standard procedure was developed using both fresh and evaporated oils with a wide range of viscosities. Test parameters that were evaluated included temperature, oil viscosity, time, and test-surface area. A recent study has also determined that the relative adhesiveness of different oils is independent of the type of surface material used (Jokuty et al., 1996). 

Volatile Organic Compounds

Benzene, toluene, ethylbenzene, and xylenes (BTEX), and substituted benzenes are the most common aromatic compounds in petroleum, making up to a few percent of the total mass of some crude oils. They are the most soluble and mobile fraction of crude oil and many petroleum products, and as such, frequently enter soil, sediments, and ground water because of accidental spills, leakage of petroleum fuels from storage tanks and pipelines, and improper oil waste disposal practices. BTEX are hazardous carcinogenic and neurotoxic compounds and are classified as priority pollutants regulated by Environment Canada and the US Environmental Protection Agency. 

A rapid, reliable, and effective method for direct determination of BTEX plus C3-substituted benzenes has been developed using gas chromatography with mass spectrometric detection (GC/MS). Details of the method are given in a paper by Wang et al. (1995). 

GC Analysis

Detailed compositional analysis of petroleum can be obtained using gas chromatography with flame ionization detection (GC/FID) and gas chromatography/mass spectrometry (GC/MS). A method developed at ESD can provide distributions of n-alkanes, polyaromatic hydrocarbons, and important biomarker compounds such as hopanes (Wang et al., 1993). 

Surface Tension and Interfacial Tension 

Interfacial tension is the force of attraction between the molecules at the interface of two fluids. At the air/liquid interface, this force is often referred to as surface tension. The SI units for interfacial tension are millinewtons per metre (mN/m). These are equivalent to the former units of dynes per centimetre (dyne/cm). 

The surface tension of an oil, together with its viscosity, affects the rate at which an oil spill spreads. Air/oil and oil/water interfacial tensions can be used to calculate a spreading coefficient which gives an indication of the tendency for the oil to spread. It is defined as: 

Spreading Coefficient = SWA - SOA - SWO

where SWA is water/air interfacial tension, SOA is oil/air interfacial tension, and SWO is water/oil interfacial tension. 

Spreading to a thin slick is likely if the spreading coefficient of an oil is greater than zero, and the higher the spreading coefficient, the faster the spreading will occur (Twardus, 1980). 

Unlike density and viscosity, which show systematic variations with temperature and degree of evaporation, interfacial tensions of crude oils and oil products show no such correlations. Nor is there any correlation to viscosity (Jokuty et al., 1995). 

A single ASTM method, D 971 - Standard Test Method for Interfacial Tension of Oil Against Water by the Ring Method (ASTM, 1996a), is applicable to the measurement of oil/water interfacial tensions. At EETD, measurements were taken using a Fisher Surface Tensiometer Model 21. ESD measurements made prior to 1993 used a CSC Du Nouy Tensiometer #70545. Since 1993, ESD has made interfacial and surface tension measurements using a Kruss Digital Tensiometer K10ST. This instrument uses the Du Nouy principle for measuring interfacial tension, as recommended in the ASTM method. Unlike manually operated ring tensiometers, the maximum deformation of the lamella is detected electronically, and occurs before the ring pulls completely through the interface. This results in interfacial tensions that are slightly lower than those measured manually. Repeatability is +/-2% of the mean. For more details, see the Appendix of Methods. 

Boiling Point Distributions

In the oil refining industry, boiling range distribution data are used to evaluate new crudes, to confirm crude quality before purchase, to monitor crude quality during transportation, and to provide information for the optimization of refinery processes. From the point of view of oil analysis for environmental purposes, boiling range distributions provide an indication of volatility and component distribution. In addition, this data can be used as input to some oil spill modelling programs. Boiling range distribution data may also prove to be useful in the development of equations for predicting evaporative loss. 

Traditionally, boiling range distributions have been determined by distillation. 'Yield on crude' data are still widely reported in the oil assay literature, providing information on the yield of specific fractions obtained from a crude oil. Although by no means universal, the following is a commonly used set of petroleum fractions and their corresponding true boiling point (TBP) cut points: 
 
Product TBP Cut Points, C TBP Cut Points, F
Light straight-run gasoline C5-70 C5-158
Light naphtha 70-100 158-212
Medium naphtha 100-150 212-302
Heavy naphtha 150-190 302-374
Light kerosene 190-235 374-455
Heavy kerosene 235-265 455-536
Atmospheric gas oil 265-343 536-650
Vacuum gas oil 343-565 650-1049
Atmospheric residue >343 >650
Vacuum residue >565 >1049

Atmospheric and vacuum distillation techniques have largely been replaced by 'simulated' distillation methods. These methods use low resolution gas chromatography and correlate retention times to hydrocarbon boiling points. ASTM methods D 2887 - Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography and D 3710 - Standard Test Method for Boiling Range Distribution of Gasoline and Gasoline Fractions by Gas Chromatography use external standards composed of n-alkanes (ASTM, 1996a). ASTM method D 5307 - Standard Test Method for Determination of Boiling Range Distribution of Crude Petroleum by Gas Chromatography is very similar to D 2887, but requires two runs to be made with each sample, one of which uses an internal standard (ASTM, 1996a). The amount of material boiling above 538 oC (reported as residue) is calculated from the differences between the two runs. 

At ESD, boiling point distributions are determined by simulated distillation with an AC Analytical Controls SIMDIS analyzer, comprised of a Hewlett Packard 5290 Series II gas chromatograph with an Analytical Controls Programmable Temperature Vaporizer (PTV) injector. The system uses a special high-temperature column and is capable of determining boiling point distributions between 35 oC and 750 oC. For more details, see the Appendix of Methods. 

Metal Content 

Metal content in crude oils can provide valuable information about the origin of those oils, potentially aiding in identifying the source of oil spills. Crude oil assays often include nickel and vanadium contents due to the detrimental effects of these metals on catalysts used in cracking and desulphurization processes. In lubricating oils, metal contents can provide information on both the types of additives used in the oil and on the wear history of the equipment being lubricated. ASTM method D 5185 - Standard Test Method for Determination of Additive Elements, Wear Metals, and Contaminants in Used Lubricating Oils and Determination of Selected Elements in Base Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), (ASTM, 1996a) can be used to determine over 20 different metals in a variety of petroleum products. 

To overcome problems inherent in the direct analysis of xylene solutions by ICP/AES, a method was developed at ESD using microwave digestion of oils with nitric acid (Cao, 1992; Fingas et al., 1995). 

Sulphur 

The sulphur content of a crude oil is important for a number of reasons. Downstream processes such as catalytic cracking and refining will be adversely affected by high sulphur contents. During an oil spill, the sulphur content becomes a health and safety concern for cleanup personnel. In addition, if high sulphur oils are burning, they can produce dangerous levels of sulphur dioxide. 

The total sulphur content of oil can be determined by numerous standard techniques. ASTM method D 129 - Standard Test Method for Sulfur in Petroleum Products (General Bomb Method) (ASTM, 1996a) is applicable to petroleum products of low volatility and containing at least 0.1 mass percent sulphur (ASTM, 1996a). Sulphur contents from EETD and ESD were determined using a Horiba MESA 200 sulphur and chlorine analyzer, in accordance with ASTM method D 4294 - Standard Test Method for Sulfur in Petroleum Products by Energy-Dispersive X-Ray Fluorescence Spectroscopy (ASTM, 1996a). This method is applicable to both volatile and non-volatile petroleum products with sulphur concentrations ranging from 0.05 to 5 mass percent. 

Aqueous Solubility

The solubility of oil in water can be determined by bringing to equilibrium a volume of oil and water, and then analyzing the water phase. This analysis can be done by purging and trapping the dissolved hydrocarbons or, alternatively, directly analyzing the headspace above the water. 

Since oil is a complex mixture of components and each component has a different solubility in water, an oil's aqueous solubility is expressed as the cumulative concentration of the individually dissolved components. The composition and concentration of the solubilized mixture will depend upon conditions used during equilibration. The term 'solubility' as applied to oils is being replaced by the technically more precise term 'water-soluble fraction'. The values reported in this catalogue were taken from those studies where an excess of oil was used (oil-to-water volume ratios of at least 1:20) and where the processes of evaporation and oil-in-water emulsification were prevented. Results reported by ESD were obtained as described in the Appendix of Methods. 

Toxicity 

Toxicity values in this catalogue may be reported as: 

LC50: 

Median lethal concentration is the estimated concentration of a compound that will cause death to 50 percent of the test population in a specified time after exposure. In most instances, LC50 is statistically derived by analysis of mortalities in various test concentrations after a fixed period of exposure. 

EC50: 

Median effective concentration is used when an effect other than death is the observed endpoint. EC50 is the estimated concentration of the compound in water that will have a specific effect on 50 percent of the test population in a specified time after exposure. As with LC50, the EC50 is generally derived statistically. 

TLm: 

Median tolerance limit; a term sometimes used instead of EC50. 

Biological Oxygen Demand (BOD) 

Also called 'biochemical oxygen demand', this is the standard way of describing how much oxygen, dissolved in water, is consumed by biological oxidation of the chemical during the stated period of time. The unit lb/lb indicates the pounds of oxygen consumed by each pound of chemical during the time stated. When given in percent, the values indicate the pounds of oxygen consumed by each 100 pounds of chemical during the time stated (CHRIS, 1991). 

References 

ACGIH, 1996 Threshold Limit Values for Chemical Substances and Physical Agents; Biological Exposure Indices, American Conference of Governmental Industrial Hygienists ACGIH, Cincinnati, Ohio, 1996. 

American Petroleum Institute, Petroleum Measurement Tables - Volume XI/XII, American Society for Testing and Materials, Philadelphia, Pennsylvania, 1982. 

ASTM, 1996 Annual Book of ASTM Standards - Section 5 Petroleum Products, Lubricants, and Fossil Fuels,, American Society for Testing and Materials, West Conshohocken, Pennsylvania, 1996a. 

ASTM, 1996 Annual Book of ASTM Standards - Section 14, American Society for Testing and Materials, West Conshohocken, Pennsylvania, 1996b. 

Cao, J.R., Microwave Digestion of Crude Oils and Oil Products for the Determination of Trace Metals and Sulphur by Inductively-Coupled Plasma Atomic Emission Spectroscopy, Environment Canada Manuscript Report Number EE-140, Ottawa, Ontario, 82 pp., 1992. 

CHRIS, Chemical Hazards Response Information System (CHRIS), United States Coast Guard, Department of Transportation, Washington, D.C., 1991. 

Dyroff, George V. (ed.), Manual on Significance of Tests for Petroleum Products: 6th Edition, American Society for Testing and Materials, Philadelphia, Pennsylvania, 1993. 

Esso Petroleum Canada, Product Information - Lubricants and Specialties (7th edition), 1990. 

Fingas, M.F., "Chemistry of Oil and Modelling of Spills", Journal of Advances in Marine Technology Conference, vol. 11, pp. 41-63, 1994. 

Fingas, M.F., AThe Evaporation of Oil Spills@, Proceedings of the 18th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 43-60, 1995. 

Fingas, M.F., W.S. Duval, and G B. Stevenson, The Basics of Oil Spill Cleanup, Environment Canada, Ottawa, Ontario, 1979. 

Fingas, M.F., V.M. Dufort, K.A. Hughes, M.A. Bobra, and L.V. Duggan, "Laboratory Studies on Oil Spill Dispersants", Chemical Dispersants - New Ecological Approaches, M. Flaherty, (ed.), ASTM STP 1084, American Society for Testing and Materials, Philadelphia, Pennsylvania, pp. 207-219, 1989. 

Fingas, M.F., D.L. Munn, B. White, R.G. Stoodley, and I.D. Crerar, "Laboratory Testing of Dispersant Effectiveness", Proceedings of the 1989 Oil Spill Conference, American Petroleum Institute, Washington, D.C., pp. 365-373, 1989. 

Fingas, M.F., D.A. Kyle, I.E. Bier, A. Lukose, and E.J. Tennyson, "Physical and Chemical Studies on Oil Spill Dispersants: The Effect of Energy", Proceedings of the 14th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 87-106. 1991. 

Fingas, M.F., D.A. Kyle, and E.J. Tennyson, "Physical and Chemical Studies on Oil Spill Dispersants: Effectiveness Variation with Energy", Proceedings of the 15th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 135-142, 1992. 

Fingas, M.F., D.A. Kyle, and E.J. Tennyson, "Physical and Chemical Studies on Dispersants: The Effect of Dispersant Amount on Energy", Proceedings of the 16th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 861-876, 1993. 

Fingas, M.F., B. Fieldhouse, L. Gamble, and J. Mullin, AStudies of Water-in-Oil Emulsions: Stability Classes and Measurement@, Proceedings of the 18th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 21-42, 1995a. 

Fingas, M.F., D.A. Kyle, P. Lambert, Z. Wang, and J. Mulling, AAnalytical Procedures for Measureing Oil Spill Dispersant Effectiveness in the Laboratory@, Proceedings of the 18th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 339-354, 1995b. 

Fingas, M.F., F. Ackerman, P. Lambert, K. Li, Z. Wang, J. Mullin, L. Hannon, D. Wang, A. Steenkammer, R. Hiltabrand, R. Turpin, and P. Campagna, AThe Newfoundland Offshore Burn Experiment: Further Results of Emissions Measurement@, Proceedings of the 18th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 915-995, 1995c. 

Jokuty, P., M.F. Fingas, S. Whiticar, and B. Fieldhouse, A Study of Viscosity and Interfacial Tension of Oils and Emulsions, Environment Canada Manuscript Report Number EE-153, 50 pp., Ottawa, Ontario, 1995. 

Jokuty, P., S. Whiticar, K. McRoberts, and J. Mullin, AOil Adhesion Testing - Recent Results@, Proceedings of the 19th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 9-27, 1996. 

Mackay, D. and W. Zagorski, Studies of Water-in-Oil Emulsions, Environment Canada Manuscript Report Number EE-34, Ottawa, Ontario, 100 pp., 1982. 

Schramm, L.L. (ed.), Emulsions. Fundamentals and Applications in the Petroleum Industry, American Chemical Society, Washington, D.C., p. 386, 1992. 

Speight, J.G., The Chemistry and Technology of Petroleum, Marcel Dekker, Inc., New York, New York, 1991. 

Twardus, E.M., A Study to Evaluate the Combustibility and Other Physical and Chemical Properties of Aged Oils and Emulsions, Environment Canada Manuscript Report Number EE-5, Ottawa, Ontario, 1980. 

Wang, Z., M. Fingas, and K. Li, "Fractionation of ASMB Oil and Identification and Quantitation of Aliphatic, Aromatic and Biomarker Compounds by GC/FID and GC/MS", Proceedings of the 16th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 11-44, 1993. 

Wang, Z., M. Fingas, M. Landriault, L. Sigouin, and N. Xu, AIdentification of Alkyl Benzenes and Direct Determination of BTEX and (BTEX + C3-Benzenes) in Oils by GC/MS@, Proceedings of the 18th Arctic and Marine Oil Spill Program Technical Seminar, Environment Canada, Ottawa, Ontario, pp. 141-164, 1995.