The most important tests conducted on solvents are shown in Table 2. These tests are of two general types. Quality con- trol tests are those used to test shipments for uniformity and compliance with specifications, and evaluation tests are those conducted on new materials to determine their proper- ties and suitability for use. As a rule, the quality control tests are simpler. Some tests may be used for both purposes.
The following paragraphs address sampling techniques for petroleum solvents and discuss the purposes and principles of the tests listed in Table 2. Specific details on the various tests can be found in theAnnual Book of ASTM Standards, volumes 5.01, 5.02, 5.03, 5.04, 5.05, 6.01, 6.02, 6.04, 10.03, and 15.05.
Sampling
Because of the standards set for petroleum solvents, it is essen- tial to employ the correct techniques when taking samples for tests. Mishandling, or the slightest trace of contaminant, can give rise to misleading results. Sampling methods are described in ASTM D4057, Standard Practice for Manual Sampling of Petroleum and Petroleum Products. Special care is necessary to ensure that containers are scrupulously clean and free from odor. Samples should be taken with minimum disturbance, so as to avoid loss of volatile components. In the case of the light- est solvents, it may be necessary to chill the sample. While wait- ing to be tested, samples should be kept in a cool, dark place to ensure that they do not discolor or develop odors.
Specific Gravity (Relative Density)
The determination of specific gravity (relative density) serves two purposes: it provides a check on the uniformity of ship- ments, and it permits calculation of the weight per gallon.
Specific gravity is defined as the ratio of a weight of a given volume of material to the weight of an equal volume of water under specified conditions. Manual determination of the specific gravity of petroleum solvents can be done using a glass hydrometer or pycnometer by ASTM D891, Standard Test Method for Specific Gravity of Liquid Indus- trial Chemicals. An instrumental method of determining spe- cific gravity, ASTM D4052, Standard Test Method for Density and Relative Density by Digital Density Meter, has gained popularity because of its ease of operation and digital dis- play of results.
In the past, producers of petroleum solvents used Ameri- can Petroleum Institute (API) gravity instead of specific
TABLE 2—ASTM Tests Commonly Conducted on Solvents
Specific gravity (relative density) D891 A or B or D4052 Distillation
(a) petroleum type solvents D86, D7344, or D7345
(b) aromatic solvents D850
(c) other solvents D1078
Flash point
(a) Tag closed-cup tester D56 (b) Cleveland open-cup tester D92 (c) Pensky-Martens closed-cup tester D93 (d) Tag open-cup tester D1310
Evaporation rate D3539
Copper corrosion, aromatic hydrocarbon
D849
Sulfur content
Trace sulfur by oxidative microcoulometry
D3120
Sulfur by hydrogenolysis and rateo- metric colorimetry
D4045
Sulfur by GC and selective sulfur detection
D5623
Sulfur in aromatic solvents D4045 Sulfur in light hydrocarbons by
ultraviolet (UV) fluorescence
D5453
Dilution ratio in nitrocellulose solutions
D1720
Viscosity of nitrocellulose solutions D1343
Color D156, D1209, D848,
D5386, or D6045
Kauri-butanol value D1133
Aniline point and mixed-aniline point
D611
Bromine index D1492, D2710, or D5776
Water D6304, D7375, or E 1064
gravity. However, this practice has virtually been discontin- ued in favor of measured specific gravity.
For figuring formula yields and important composi- tional relationships, paint laboratories must have a list of raw materials that includes the weight per gallon of all liq- uid materials at normal operating temperature. When the specific gravity of solvents is determined at the customary 15.6/15.6C (60/60F), a temperature conversion factor must be used to obtain the specific gravity at 20C (68F). This temperature conversion factor differs from solvent to sol- vent. The corrected specific gravity must then be converted to pounds per gallon.
Distillation
The significance of distillation results is based on the close relationship to volatility properties, which, in turn, largely governs evaporation rate. ASTM D86, Standard Test Method for Distillation at Atmospheric Pressure, is used for solvents with a wide distillation range (this includes the common aliphatic and aromatic naphtha solvents). Dis- tillation of pure aromatic solvents like toluene and xylene is done using ASTM D850, Standard Test Method for Distil- lation of Industrial Aromatic Hydrocarbons and Related Materials. For other solvents with a narrow distillation range (alcohols, esters, ketones, etc.), ASTM D1078, Stand- ard Test Method for Distillation Range of Volatile Organic Liquids, is used. Regardless of solvent type, a very narrow distillation range has no direct advantage in coatings.
However, it may have significance as an indication of the degree of purity, especially for oxygenated solvents. Two recently developed distillation methods that are applicable to solvents are: ASTM D7344, Standard Test Method for Petroleum Products (Mini Method), and ASTM D7345, Standard Test Method for Petroleum Products (Micro Method). These two new distillation methods make use of less than 10 mL sample and test parameters quite distinct from D86, D1078, and D850.
Flash Point
The flash point of a liquid is the lowest temperature cor- rected for atmospheric pressure at which application of an ignition source causes the vapor above the specimen to ignite. Flash point is indicative of potential fire hazard. The most common method for determining flash point of sol- vents is using ASTM D56, Flash Point by Tag Closed-Cup Tes- ter, which confines the vapor until the instant an ignition source is applied. However, Department of Transportation (DOT) regulations on the shipping of flammable solvents are based on ASTM D56, ASTM D3828, Standard Test Method for Flash Point by Small Scale Closed Cup Tester, or ASTM D3278, Standard Test Method for Flash Point of Liquids by Small Scale Closed Cup Tester. There are other test methods of flash point determination for other types of materials. In the past, the determination of flash point was based on the use of a test flame and visual observation of the occurrence of the flash point. The advent of automatic flash point instruments made other sources of ignition possible such as electric ignitors and arcs, in addition to automatic detection of flash point using changes in ionization current, thermal properties, and pressure.
In mixtures of solvents and in coatings, the flash point is substantially that of the lowest flash point component that is present in appreciable amount.
Evaporation Rate
Although there is a correlation between distillation range and evaporation rate, the relationship is not direct. Because it is important, several methods of measuring evaporation rates of straight solvents (not the solvent in a film coating) have been developed by various commercial and govern- mental organizations. In the past, simple gravimetric or vol- umetric procedures were used to measure evaporation rate.
However, the determination of solvent evaporation rate is currently described in ASTM D3539, Standard Test Method for Evaporation Rates of Volatile Liquids by Shell Thin- Film Evaporometer. In this method, a measured volume of liquid solvent is spread on a known area of filter paper that is suspended from a sensitive analytical balance under a controlled environment cabinet. The weight loss of the fil- ter paper/solvent liquid is measured as a function of time as the solvent evaporates.
Evaporation rates are usually expressed relative to n- butyl acetate, which is assigned a value of one (or 100). A value of 0.4 (or 40) means that the solvent evaporates 40 % as fast as
n-butyl acetate, and a value of 2.5 (or 250) means 2.5 times faster.
There is a formula for calculating evaporation rates from distillation temperatures. However, in view of the com- plexity of the calculations, direct determination would prob- ably involve a shorter time and be more accurate.
Color
Most solvents are “water-white” or clear and essentially col- orless. Color is an important specification requirement. If a solvent has a color worse than the specification limit, it may be an indication of (1) inadequate processing; (2) contamina- tion that might have occurred during storage or distribution (e.g., pick-up of rust from tanks, pipes, or extracted from improper tank linings or hoses); or (3) oxidative degradation as a result of aging.
There are two visual test methods used for measuring the color of solvents: ASTM Method D156, Saybolt Color of Petroleum Products (Saybolt Chromometer Method), and D1209, Color of Clear Liquids (Platinum-Cobalt Scale). D156 is used only for hydrocarbon solvents. D1209 is used mainly for oxygenated solvents, but is gaining acceptance for hydro- carbon solvents as well. More recently, color measurement by automatic tristimulus colorimetry has gained acceptance and popularity with petroleum solvent manufacturers because of better precision and less subjectivity. ASTM D5386, Color of Liquids Using Tristimulus Colorimetry, is used by the aromatic solvent industry to report correlated or equivalent D1209 color values. ASTM D6045, Color of Petro- leum Products by the Automatic Tristimulus Method, can report correlated or equivalent D156 color.
Kauri Butanol Value
ASTM D1133, Standard Test Method for Kauri Butanol Value of Hydrocarbon Solvent, is used to determine relative solvent power. The kauri-butanol (K-B) value is the number of milliliters of the solvent at 25C (77F) required to pro- duce a defined degree of turbidity when added to a 20 g sample of a standard solution of kauri gum resin inn-butyl alcohol. For K-B values of 60 and over, the reference stand- ard is toluene, which has an assigned value of 105. For K-B values under 60, the reference standard is a blend of 75 %
n-heptane and 25 % toluene. This blend has an assigned value of 40. Higher values indicate greater solvent power.
The K-B value of products that are classified as regular mineral spirits normally varies between 34 and 44; xylene is 93; and aromatic naphtha solvents range all the way from 55 to 108.
Aniline Point and Mixed Aniline Point
ASTM D611, Standard Test Method for Aniline Point and Mixed Aniline Point of Petroleum Products and Hydrocar- bon Solvents, is another test method for determining the sol- vent power of hydrocarbon solvents. It is a more precise technique than the test method for K-B value, and the results have better correlation with performance in some coatings.
The two methods may indicate a reversal of solvent power when applied to solvents that are in the same range. There- fore, in evaluation testing, it is best to employ both methods.
For solvents with very high aromatic content, such as those of the high-flash aromatic naphthas, the mixed aniline point is determined instead of aniline point. Mixed aniline point uses a sample made up of 5 mL of the solvent being tested and 5 mL of n-heptane. Automatic instruments are becom- ing more prevalent these days in the determination of ani- line and mixed aniline points of solvents.
Bromine Index
Olefinic and other unsaturated hydrocarbon impurities in solvents could have some deleterious adverse effect on cer- tain solvent applications. Because of the reactivity of the ole- finic bond, the color of solvents could be negatively impacted by unsaturated chemical species. When solvents are used as reaction solvents, unsaturated hydrocarbon impurities have to be monitored accurately to prevent deteri- oration of catalyst materials. ASTM D2710, Test Method for Bromine Index of Petroleum Hydrocarbons by Electrometric Titration, is commonly used. For aromatic hydrocarbons, similar test methods, D1492, Test Method for Bromine Index of Aromatic Hydrocarbons by Coulometric Titration, and D5776, Test Method for Bromine Index for Aromatic Hydro- carbons by Electrometric Titration, are used. All these test methods for determining bromine index do not distinguish the type of unsaturated chemical species in the solvent.
Sulfur
Previous to the advent of accurate quantitative determina- tion of sulfur content of solvents, copper strip corrosion tests were used to detect the presence and determine the rel- ative amounts of sulfur compounds in solvents. Sulfur com- pounds in the form of mercaptans and di-sulfides are objectionable because they impart odor and may cause dark- ening of cooked varnishes and resins.
ASTM D849, Standard Test Method for Copper Corro- sion of Industrial Aromatic Hydrocarbons, is used for the determination of sulfur in aromatic hydrocarbons, while ASTM D130, Standard Test Method for Detection of Copper Corrosion from Petroleum Products by the Copper Strip Tar- nish Test, is applicable for sulfur species in aliphatic hydro- carbons. With modern refining technology, copper corrosion tests have assumed less importance, although some solvent specifications still call for it occasionally.
Doctor’s Test is a qualitative test for the presence of sul- fur. It is described in ASTM D4952, Test Method for Qualita- tive Analysis for Active Sulfur Species in Fuels and Solvents
(Doctor’s Test). In recent years, quantitative instrumental analysis for sulfur content in petroleum solvents has improved tremendously, and it has gained widespread accep- tance in the petroleum and solvent industries. Among the many ASTM quantitative sulfur test methods applicable to solvents are: D3120, Test Method for Trace Quantities of Sul- fur in Light Petroleum Hydrocarbons by Oxidative Micro- coulometry; D3961, Trace Quantities of Sulfur in Liquid Aromatic Hydrocarbons by Oxidative Microcoulometry;
D4045, Test Method for Sulfur in Petroleum Products by Hydrogenolysis and Rateometric Colorimetry; D5453, Test Method for Determination of Total Sulfur in Light Hydrocar- bons, Spark-Ignition Engine Fuel, Diesel Engine Fuel, and Engine Oil by Ultraviolet Fluorescence; D5623, Test Method for Sulfur Compounds in Light Petroleum Liquids by Gas Chromatography and Sulfur Selective Detection; D6212, Test Method for Total Sulfur in Aromatic Compounds by Hydro- genolysis and Rateometric Colorimetry; D6313, Test Method for Total Sulfur in Aromatic Compounds by Hydrogenolysis and Sulfur Specific Difference Photometry; and D6428, Test Method for Total Sulfur in Liquid Aromatic Hydrocarbons and Their Derivatives by Oxidative Combustion and Electro- chemical Detection.
Dilution Ratio in Nitrocellulose Solutions
Solvent mixtures for nitrocellulose lacquers contain three classes of volatile liquids: active solvents, latent solvents (e.g., alcohols), and diluents. The active and latent solvents may be grouped together under the term “oxygenated sol- vents.” The diluents are hydrocarbon solvents, which have no solvency for nitrocellulose and are employed mainly to reduce cost without sacrifice of quality. The proportion of hydrocarbon solvents that can be used without precipita- tion of the nitrocellulose differs with the kind of hydrocar- bon. The dilution ratio test determines this proportion for particular hydrocarbon ratio and is described in ASTM D1720, Test Method for Dilution Ratio of Active Solvents in Cellulose Nitrate Solutions.
Dilution ratio = Volume of hydrocarbon solvent Volume of butyl acetate ð1ị at the end point. This ratio is roughly proportional to the aromatic content of the hydrocarbon solvent.
The dilution ratio test is also applied to oxygenated sol- vents. Oxygenated solvents differ in the amount of diluent that they will tolerate. This affects the cost of formulating with a particular oxygenated solvent. For this purpose, a sin- gle diluent, toluene, is generally employed. The amount varies with each oxygenated solvent being tested.
Viscosity of Nitrocellulose Solutions
One of the disadvantages of nitrocellulose in coatings is that the more durable grades produce solutions that have high viscosity and, therefore, low solids at a viscosity suitable for application. The viscosity of a solution is affected by the kind of solvent or mixture of solvents. ASTM D1343, Test Method for Viscosity of Cellulose Derivatives by Ball-Drop Method, describes the test for viscosity. The test is designed to determine the inherent viscosity characteristic of various grades of nitrocellulose. The test is equally suitable for com- paring the viscosity effect of solvents by varying the solvent while holding the kind and amount of nitrocellulose constant.
Applicable ASTM Standard Specifications and Test Methods
The following boxes summarize the various ASTM standard specifications applicable to petroleum solvents and give the various ASTM standard test methods that can be used for testing petroleum solvents, including cross-reference to Insti- tute of Petroleum (IP) test methods applicable to solvents.
Applicable ASTM Standard Specifications ASTM Title
Aliphatic Hydrocarbons
D235 Mineral Spirits (Petroleum Spirits, Hydrocabon Dry Cleaning Solvent)
D1836 Commercial Hexanes D3735 VM&P Naphthas Aromatic Hydrocarbons
D841 Toluene, Nitration Grade D843 Xylene, Nitration Grade D2359 Benzene, Refined 535 D3193 Ethylbenzene
D3734 High-Flash Aromatic Naphthas D4077 Cumene (Isopropyl Benzene) D4734 Benzene, Refined 545 D5136 High Purityp-Xylene
Applicable ASTM/IP Standard Test Methods
ASTM IP Title
Physical Properties Volatility
Distillation
D86 123 Distillation of Petroleum Products at Atmospheric Pressure
D850 Distillation of Industrial Aromatic Hydrocarbons and Related Materials D1078 Distillation Range of Volatile Organic
Liquids
D7344 Distillation of Petroleum Products at Atmospheric Pressure (Mini Method) D7345 Distillation of Petroleum Products at
Atmospheric Pressure (Micro Method) Flash Point
D56 Flash Point by Tag Closed-Cup Tester D92 36 Flash Point by Cleveland Open-Cup
Tester
ASTM IP Title
D93 34 Flash Point by Pensky-Martens Closed- Cup Tester
D2887 Flash Point of Liquids by Small Scale Closed-Cup Appartus
D3828 Flash Point by Small Scale Closed-Cup Tester
D6450 Flash Point by Continuously Closed- Cup Tester
Autoignition Temperature
E659 Autoignition Temperature of Liquid Chemicals
Residue
D1353 Non-Volatile Matter in Volatile Sol- vents for Use in Paint, Varnish, Lac- quer, and Related Products Density and Specific Gravity
D891 Specific Gravity of Liquid Industrial Chemicals
D1217 Density and Relative Density by Bing- ham Pycnometer
D1298 160 Density, Relative Density (Specific Gravity) by Hydrometer Method
D1555 Calculation of Volume and
Weight of Industrial Aromatic Hydrocarbons
D3505 Density and Relative Density of Pure Liquid Chemicals
D4052 Density and Relative Density of Liquids by Digital Density Meter Freezing Point
D852 Solidification Point of Benzene D1015 Freezing Points of High-Purity
Hydrocarbons
D1493 Solidification Point of Industrial Aromatic Hydrocarbons
D2500 Cloud Point (Manual Method)
D5771 Cloud Point (Optical Detection Stepped Cooling Method) D5772 Cloud Point (Linear Cooling Rate
Method)
D5773 Cloud Point (Constant Cooling Rate Method)
Viscosity
D445 Kinematic Viscosity of Transparent and Opaque Liquids
D1343 Viscosity of Cellulose Derivative by Ball Drop Method
ASTM IP Title Color
D156 Saybolt Color of Petroleum
Products (Saybolt Chromometer Method)
D848 Acid Wash Color of Industrial Aromatic Hydrocarbons D1209 Color of Clear Liquids (Platinum-
Cobalt Scale)
D5386 Color of Liquids Using Tristimulus Colorimetry
D6045 Color of Petroleum Products by the Automatic Tristimulus Method
Refractive Index
D1218 Refractive Index and Refractive Dispersion of Hydrocarbon Liquids
Solvency
D611 Aniline Point and Mixed Aniline Point of Petroleum Products
D1133 Kauri-Butanol Value of Hydrocarbon Solvents
D1720 Dilution Ratio of Active Solvents in Cellulose Nitrate Solutions Odor
D1296 Odor of Volatile Solvents and Diluents
Definitions and Handling
D268 Sampling and Testing Volatile Sol- vents and Chemical Intermediates D1250 200 Petroleum Measurement Tables D4057 Manual Sampling of Petroleum and
Petroleum Products
D4177 Automatic Sampling of Petroleum
and Petroleum Products Chemical Properties
Bulk Composition
D1016 Purity of Hydrocarbons from Freezing Points
D1319 156 Hydrocarbon Types in Liquid Petro- leum Products by FIA
D2008 Ultraviolet Absorbance and Absorp- tivity of Petroleum Products D2268 Analysis of High-Purity n-Heptane
andIsooctane by Capillary GC D2308 C8Aromatic Hydrocarbon Analysis by
GC
D3797 Analysis ofo-Xylene by GC
ASTM IP Title
D3798 Analysis ofp-Xylene by GC
D4492 Analysis of Benzene by GC
D5399 Boiling Point Distribution of Hydro- carbon Solvents by GC
Impurity Determination Hydrocarbon
Types
D2360 Trace Impurities in Monocylic Aromatic Hydrocarbons
D3257 Aromatics in Mineral Spirits by GC D4367 Benzene in Mineral Spirits
D5060 Determining Impurities in High-Purity Ethylbenzene by GC
D5917 Trace Impurities in Monocyclic Aromatic Hydrocarbons by GC and External Calibration
D1492 Bromine Index of Aromatic Hydrocar- bon by Coulometric Titration
D2710 Bromine Index of Petroleum
Hydrocarbon by Electrometric Titration
D5776 Bromine Index of Aromatic
Hydrocarbon by Electrometric Titration
D6229 Trace Benzene in Hydrocarbon Sol- vent By Capillary GC
Sulfur
D130 154 Copper Corrosion from Petroleum Products by Copper-Strip Tarnish Test
D849 Copper Corrosion of Industrial Aromatic Hydrocarbons
D853 Hydrogen Sulfide and Sulfur dioxide Content (Qualitative) of Industrial Aromatic Hydrocarbon
D1266 107 Sulfur in Petroleum Products (Lamp Method)
D1685 Traces of Thiophene in Benzene by Spectrophotometry
D3120 Trace Quantities of Sulfur in Light Petroleum Hydrocarbon by Oxidative Microcoulometry
D4045 Sulfur in Petroleum Products by Hydrogenolysis and Rateometric Colorimetry
D4735 Traces of Thiophene in Refined Benzene by GC
D4952 Qualitative Analysis of Active Sulfur Species in Fuels and Solvents (Doctor’s Test)