United States Prevention, Pesticides EPA712-C-96-034 Environmental Protection and Toxic Substances August 1996 Agency (TS-7101) &EPA Product Properties Test Guidelines OPPTS 830.7220 Boiling Point/Boiling Range ------- INTRODUCTION This guideline is one of a series of test guidelines that have been developed by the Office of Prevention, Pesticides and Toxic Substances, United States Environmental Protection Agency for use in the testing of pesticides and toxic substances, and the development of test data that must be submitted to the Agency for review under Federal regulations. The Office of Prevention, Pesticides and Toxic Substances (OPPTS) has developed this guideline through a process of harmonization that blended the testing guidance and requirements that existed in the Office of Pollution Prevention and Toxics (OPPT) and appeared in Title 40, Chapter I, Subchapter R of the Code of Federal Regulations (CFR), the Office of Pesticide Programs (OPP) which appeared in publications of the National Technical Information Service (NTIS) and the guidelines pub- lished by the Organization for Economic Cooperation and Development (OECD). The purpose of harmonizing these guidelines into a single set of OPPTS guidelines is to minimize variations among the testing procedures that must be performed to meet the data requirements of the U. S. Environ- mental Protection Agency under the Toxic Substances Control Act (15 U.S.C. 2601) and the Federal Insecticide, Fungicide and Rodenticide Act (7U.S.C. I36,etseq.). Final Guideline Release: This document is available from the U.S. Government Printing Office, Washington, DC 20402 on The Federal Bul- letin Board. By modem dial 202-512-1387, telnet and ftp: fedbbs.access.gpo.gov (IP 162.140.64.19), internet: http:// fedbbs.access.gpo.gov, or call 202-512-0132 for disks or paper copies. This guideline is available in ASCII and PDF (portable document format) from the EPA Public Access Gopher (gopher.epa.gov) under the heading "Environmental Test Methods and Guidelines." ------- OPPTS 830.7220 Boiling point/boiling range. (a) Scope—(1) Applicability. This guideline is intended to meet test- ing requirements of both the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) (7 U.S.C. 136, et seq.) and the Toxic Substances Control Act (TSCA) (15 U.S.C. 2601). (2) Background. The source materials used in developing this har- monized OPPTS test guideline are the OPPT guideline under 40 CFR 796.1220 Boiling Point/Boiling Range, OPP guideline 63-6 Boiling Point (Pesticide Assessment Guidelines, Subdivision D: Product Chemistry, EPA Report 540/9-82-018, October 1982) and OECD guideline 103 Boiling Point/Boiling Range. (b) Introduction. (1) Five methods used to determine the boiling point are described in this guideline: The ebulliometric method is based on the ASTM D 1120-72; the distillation method is based on the standards ISO R 918 and the draft ISO DIS 4626, BS 4359/68, BS 4591/71, DIN 53171; the Siwoloboff method is based on JIS K 0064-1966; the photocell detection method is based on the manufacturer's manual under paragraph (e)(4) of this guideline; the Dynamic Method was tested in the OECD Laboratory Intercomparison Testing Programme, part I, 1979, for vapor pressure determination. (2) Qualifying statement. The methods and devices described in this test guideline can be applied to liquids, provided that these do not undergo chemical reaction at temperatures below the boiling point (e.g., autoxidation, rearrangement, degradation, etc.). (c) Method. (1) Application and limits of test. The boiling point of a substance is an environmentally relevant physical chemical property be- cause it is important for identification purposes and is one factor influenc- ing the states in which the substance will exist in the environment. (2) The emphasis in this test guideline has been placed on the descrip- tion of the method using photocell detection, because this method allows the determination of melting as well as boiling points. Moreover, the meas- urements can be performed automatically. (3) The dynamic method has the advantage that it can also be applied for the determination of vapor pressure and that it is not necessary to cor- rect the boiling temperature to the normal pressure (101.325 kPa) because the standard pressure can be adjusted during the measurement. However, this method is not at present automated. (For a detailed description, see OPPTS 830.7950 for the vapor pressure curve. (4) Note: In the literature, different boiling points are sometimes quoted for the same substance. These differences are due to such variables as the dimension of the apparatus (for example, the fit of the thermometer), the type of the thermometer, the stem correction, the pressure correction, ------- and the accuracy of the pressure measurement. Therefore, the above-men- tioned international and national standardized methods contain precise re- quirements for these specified conditions. (5) The influence of impurities on the determination of the boiling point depends greatly upon the kind of impurity. Thus, the effect can be considered if a highly volatile solvent is present in the sample. Impurities will usually increase/decrease the measured boiling temperature. (6) Definitions and units, (i) The standard boiling point is described as the temperature at which the pressure of the saturated vapor of a liquid is the same as the standard pressure. (ii) The measured boiling point is dependent on the atmospheric pres- sure. This dependence can be described quantitatively by the Clausius- Clapeyron equation as follows: log p = - AHv/2.3 RT where p is the vapor pressure of the substance, AHV is its heat of vaporiza- tion, and R is the universal molar gas constant, R = 8.31441 J moHK-1 The temperature T is expressed in K). (iii) The temperature at the boiling point (boiling temperature) is stat- ed in K, with regard to the ambient pressure during the measurement. If no pressure is given, the result refers to a standard pressure of 101.325 kPa. (iv) Conversions: 100 kPa = 133 Pa = 1 Pressure (units kPa) 1 bar= 0.1 MPa1 mm Ha = 1 torr2 Temperature (units K) t = T- 273. 15 t in °C. and T in K 1 "Bar" units are still permissible but not recommended. 2 The units mm Hg and torr are no longer permissible. (A) At small deviations from the normal pressure (max. + 5 kPa), the boiling point temperatures are normalized to Tn by means of the fol- lowing number-value-equation by Sidney-Young: Tn=T + fTAp where: Ap = (101.325 - p) (note sign) p = barometer measurement in kPa fx = rate of change of boiling point with pressure in K/kPa ------- T = measured boiling temperature in K Tn = boiling temperature corrected to normal pressure in K (B) The temperature-correction factors fx and equations for their ap- proximation are included in the international and national standards men- tioned in paragraph (e)(2) of this guideline for many substances. For exam- ple, the DIN 53171 method mentions the following rough corrections for solvents included in paints under the following table 1: Table 1.—Temperature Correction Factors fT Temperature (T,K) 323.15 348.15 373.15 398.15 423.15 448.15 Correction factor (fT, K/kPa) 0.26 0.28 0.31 0.33 0.35 0.37 Temperature (T, K) 473.15 498.15 523.15 548.15 573.15 Correction factor (fT, K/kPa) 0.39 0.41 0.44 0.45 0.47 (C) A table of temperature-correction factors for organic solvents (see ISO/DIS 4626 is included in the following table 2: Table 2.—Temperature-Correction Factors for Organic Solvents (See ISO/DIS 4626) Product Acetone Aceto nit rile Allyl alcohol Allyl chloride n-Amyl acetate n-Amyl alcohol Aromatic solvent naptha Benzene Isobutyl acetate n-Butyl acetate sec-Butyl acetate Isobutyl alcohol n-Butyl alcohol sec-Butyl alcohol terf-Butyl alcohol p-terf-Butyl toluene Cumene Cyclohexane Cyclohexanone Diacetone alcohol Diisobutyl ketone Diisobutylene 1,2-Dichloroethane Dichloromethane Diethyleneglycol Diethylene glycol mono-n-butyl ether Diethylene glycol monoethyl ether Diethylene glycol monomethyl ether Thermometer °C 39 40 40 38 102 41 42 40 41 41 40 40 40 40 40 104 102 40 102 102 103 40 40 38 106 105 104 104 Boiling at 101.325 kPa 56.1 81 6 969 45 1 149.5 138.0 80 1 1173 126 1 112.4 107.9 117.7 995 825 1928 152.4 80.7 155.7 1692 1693 101 4 83.5 39.8 245.8 2304 201.9 193.8 Rate of change of boiling p K'°C/0.1 kPa (°C/mbar) 0.029 0032 0028 0029 0.036 0.031 0.037 0032 0034 0034 0.034 0.027 0.028 0026 0025 0042 0.038 0.033 0.038 0038 0038 0034 0.032 0.028 0.038 0038 0.036 0.035 oint with pressure K °C/mmHg 0.039 0043 0038 0039 0.048 0.041 0.049 0042 0045 0045 0.045 0.036 0.037 0035 0033 0056 0.051 0.044 0.051 0050 0051 0046 0.043 0.037 0.050 0051 0.048 0.047 ------- Table 2.—Temperature-Correction Factors for Organic Solvents (See ISO/DIS 4626)—Continued Product Dimethyl formamide Dipropylene glycol Diisopropyl ether Ethyl acetate Ethyl alcohol Ethyl benzene Ethylene glycol Ethylene glycol mono-n-butyl ether Ethylene glycol monoethyl ether Ethylene glycol monoethyl ether acetate Ethylene glycol monomethyl ether Ethylene glycol monoisopropyl ether 2-Ethyl hexanol Ethyl isoamyl ketone n-Hexyl acetate Hexylene glycol Isophorone Mesityl oxide 4-Methoxy-4-methyl-2-pentanone Methanol Methyl isoamyl acetate Methyl isoamyl ketone Methyl isobutyl carbinol Methyl isobutyl ketone Monoethanol amine Perchloroethylene n-Propyl acetate /so-Propyl acetate n-Propyl alcohol Isopropyl alcohol Propylene glycol Propylene oxide Pyridine Toluene Triethylene glycol Triethylene glycol monoethyl ether Trichloroethylene Vinyl acetate White spirit Xylene (isomer mixture) m-Xylene o-Xylene />Xvlene Thermometer °C 102 106 39 39 39 41 104 103 102 102 41 102 104 103 103 104 105 41 103 39 102 102 41 41 103 41 40 40 40 40 104 38 41 41 107 106 40 39 103 41 41 41 41 Boiling nnint °P at 101.325 kPa 1530 232.8 68.3 77.2 78.3 1362 1976 171 2 135.1 156.3 1245 1428 184.8 158.2 171.6 197.1 2153 1298 160.6 646 146.2 144.9 131.8 116.2 1707 121 2 101 6 885 97.2 82.3 187.6 34.3 1154 110.6 287.6 2554 87.1 727 139 1 1444 138.3 Rate of change of boiling p K'°C/0.1 kPa (°C/mbar) 0033 0.038 0.031 0.031 0.025 0037 0032 0035 0.033 0.035 0031 0033 0.034 0.037 0.038 0.034 0043 0035 0.037 0025 0.036 0.036 0.031 0.035 0030 0036 0032 0031 0.026 0.025 0.032 0.027 0035 0.035 0.038 0038 0.032 0030 0041 0.037 0037 0037 0.037 oint with pressure K °C/mmHg 0044 0.051 0.041 0.041 0.033 0049 0043 0047 0.044 0.046 0041 0044 0.046 0.049 0.050 0.045 0057 0047 0.049 0033 0.048 0.048 0.041 0.046 0040 0048 0042 0041 0.034 0.033 0.043 0.036 0046 0.046 0.050 0051 0.043 0040 0055 0.049 0049 0050 0.049 (7) Reference substances. The standard methods listed include speci- fications for calibration and evaluation substances. These compounds need not be employed in all cases when investigating a new substance. They should primarily serve to calibrate the method from time to time and to offer the chance to compare the results when another method is applied. ------- (8) Principle of the test methods. All methods for the determination of the boiling point (boiling range) are based on the measurement of the boiling temperature. (i) Determination by use of the ebulliometer. See paragraphs (e)(l) and (e)(4) of this guideline. Ebulliometers were originally developed for the determination of molecular weight by boiling point elevation, but they are also suited for exact boiling point measurements. A very simple appa- ratus is described in ASTM D 1120-72. The liquid is heated in this appara- tus under equilibrium conditions at atmospheric pressure until it boils. The determined temperature of the liquid, corrected to standard pressure, is the boiling point. (ii) Dynamic method. See paragraph (e)(2) of this guideline. This method measures the vapor recondensation temperature by means of a thermocouple in the reflux while boiling. The pressure can be varied in this method. (iii) Distillation method for boiling point (and boiling range). This method involves distillation of the liquid and measurement of the vapor recondensation temperature and determination of the amount of distillate. (iv) Method according to Siwoloboff. See paragraph (e)(2) of this guideline. A sample is heated in a sample tube which is immersed in a heat-bath liquid. A fused capillary, containing an air bubble in the lower part, is dipped in the sample tube. The temperature at which a regular string of bubbles escapes from the capillary or the temperature at which the string of bubbles stops and the fluid suddenly starts rising in the cap- illary (Siwoloboff under paragraph (e)(2) of this guideline) is determined. (v) Photocell detection. See paragraph (e)(3) of this guideline. Using the principle according to Siwoloboff. Measurements are automatic, the rising bubbles being detected photo-electrically. (9) Quality criteria. The different methods for the determination of the boiling point (boiling range) are compared with regard to their use and precision and possibility to standardize/automate in the following table 3: Table 3.—Comparison of the Methods Method of measurement Ebulliometer Dynamic method Distillation process (boiling range). According to Siwoloboff Photocell detection Differential scanning calorimetry. Approximate accuracy +1.4 K(up to 373 K)1 ±2.5 K (above 373 K) 1 +0.5 K +0.5 K +1Kto +2K +0.3 K (at 373 K) +0 5 K (up to 600 K) Ability to standardize Existing standard ASTM D 1 1 20-72 1. Possible Existing standards, e.g., ISO/ R 918, DIN 53171, BS 4591/17. Possible Possible Existing standard Automation Difficult as yet Difficult Difficult as yet Automatic method exists (see photocell detection) Measurement process works automatically Automatic method ------- Table 3.—Comparison of the Methods—Continued Method of measurement Differential thermal analysis Approximate accuracy ±2.0 K(upto 1273K) +0 5 K (up to 600 K) ±2.0 K(upto 1273K) Ability to standardize ASTM E537-76 Existing standard ASTM E537-76 Automation exists Automatic method exists 1 This accuracy is only valid for pure substances and for the simple device as, for example, described in ASTM D 1120-72; it can be improved with more sophisticated ebulliometer devices. (10) Description of the test procedures. The procedures of several of the test methods have been established by various international and na- tional standards mentioned above. Reference is made here to those stand- ards which prescribe details of preparations, test conditions, and conduct of the test. (i) Ebulliometer. See ASTM D 1120-72, Standard Test Method for Boiling Point of Engine Antifreezes, and reference under paragraph (e)(4) of this guideline. (ii) Dynamic method. See OPPTS 830.7950 for Vapour Pressure Curve, Principle of the test methods. The boiling temperature observed with an applied pressure of 101.325 kPa is recorded. (iii) Distillation process (boiling range). See ISO/R 918, Test Method for Distillation (Distillation Yield and Distillation Range); ISO 4626/1980, Volatile Organic Liquids—Determination of Boiling Range of Organic Solvents Used as Raw Materials; BS 4349/68, Method for Determination of Distillation of Petroleum Products; BS 4591/71, Method for the Deter- mination of Distillation Characteristics; DIN 53171, Losungsmittel fur Anstrichstoffe, Bestimmung des Siedeverlaufes; DIN 51751, Priifung flussiger Mineralkohlenwasserstoffe—Bestimmung des Siedeverlaufes. (iv) Method according to Siwoloboff. (A) The sample is heated in a melting point apparatus in a sample tube, with a diameter of approxi- mately 5 mm in the following figure 1: ------- FIGURE i—APPARATUS FOR THE DETERMINATION OF MELTING AND BOILING POINT (JISK 0064-1966), WITH SPECIFICATIONS IN MILLIMETERS A: MEASURING TUBE B: CORK STOPPER C: VENT D: THERMOMETER E: AUXILIARY THERMOMETER F: BATH LIQUID G: SAMPLE TUBE; MAX. 5mm OUTER DIAMETER; CAPILLARY TUBE, APPROX. 1 mm INNER DIAMETER, AND APPROX. 0.2mm TO 0.3mm WALL-THICKNESS H: SIDE TUBE (B) A capillary tube (boiling capillary) fused about 1 cm above the lower end is placed in the sample tube. The level to which the test sub- stance is filled is such that the fused section of the capillary is below the surface of the liquid. The sample tube containing the boiling capillary ------- is fastened either to the thermometer with a rubber-band or is fixed with a support from the side under the following figure 2: FIGURE 2—PRINCIPLE ACCORDING TO SIWOLOBOFF 8 ------- (C) The bath liquid is chosen according to boiling temperature. At temperatures of up to 573 K sulfuric acid or silicon oil can be used; if sulfuric acid is used, this liquid must be handled with extreme care. Liquid paraffin may only be used up to 473 K. The heating of the bath liquid should be adjusted to a temperature rise of 3 K/min at first. The bath liquid must be stirred. At about 10 K below the expected boiling point, the heating is reduced so that the rate of temperature rise is less than 1 K/min. When the boiling temperature is approached, bubbles begin to emerge from the boiling capillary. (D) The boiling point is reached when the string of bubbles stops and fluid suddenly starts rising in the capillary. The corresponding ther- mometer reading is the boiling temperature of the substance. (E) In the modified principle, under the following figure 3, the boiling point is determined in the melting point capillary which is stretched to a fine point about 2 cm in length (A) and a small amount of the sample is aspirated. The open end of the fine capillary is closed by melting, so that a small air bubble is located at the end. When heated in the melting point apparatus (B), the air bubble expands. The boiling point corresponds to the temperature at which the substance plug reaches the level of the surface of the bath liquid (C). FIGURE 3—MODIFIED PRINCIPLE (C) ------- (v) Photocell detection. (A) The sample is heated in a capillary tube inside a heated metal block. A light beam is directed via suitable holes in the block through the substance onto a precisely calibrated photocell. During the increase of the sample temperature, single air bubbles emerge from the boiling capillary. When the boiling temperature is reached, the amount of bubbles increases immensely. (B) This causes a change in the intensity of light, which is recorded by a photocell and gives a stop signal to the digital indicator reading out the temperature of a platinum resistance thermometer, located in the block. (C) This method is especially useful because it allows determinations below room temperature as low as 253.15 K (-20 °C) without any changes in the apparatus. The instrument merely has to be placed in a cold room or cooling bath. The exact execution of the boiling point determination can be obtained from the instrument manual. (vi) Differential scanning calorimetry. See ASTM E 537-76 and OECD 103. Samples of the test substance and a reference material are subjected to the same controlled temperature program. The difference in energy input necessary to maintain identical temperatures in the substance and the reference material is recorded. When the sample undergoes a tran- sition involving a change in enthalpy (endothermic on boiling), that change is indicated by a departure from the base line of the heat flow record. (vii) Differential thermal analysis. See ASTM E 537-76 and OECD 103. The difference in temperature between the substance and a reference material, which are both subjected to the same controlled temperature pro- gram, are recorded. When the sample undergoes a transition involving a change in enthalpy (endothermic in the case of boiling), that change is indicated by a departure from the base line of the temperature record. (11) General remarks, (i) The results obtained for mixtures or impure samples are to be interpreted with care. With an impure sample, for in- stance, the emergence of a low boiling component will be registered as the boiling point. Repeated determinations with the same impure sample can change the composition from measurement to measurement, due to the volatilization of low boiling components: continously increasing values are obtained in these circumstances. (ii) Liquids with a tendency to superheat can yield incorrect results. The values obtained are usually too high. This happens more frequently at higher temperatures. Distillation methods or the dynamic vapor pressure method are more suitable for these types of compound. (d) Data and reporting—(1) Treatment of results, (i) The boiling point to be determined should be a mean of at least two measurements, which are in the range of approximate accuracy indicated in table 2 under 10 ------- paragraph (c)(9) of this guideline. If determinations are not reproducible, other methods should be considered (see General remarks, above). (ii) The measured boiling points and their mean should be stated in K, and the pressure(s) at which the measurement(s) was (were) made should be recorded in kPa. Where a test substance boils over a temperature range, this range should be provided. The measured values should also be corrected to standard pressure. Estimates of accuracy should be pro- vided for all results. (iii) The method used should be indicated, including any deviations from procedures described in this test guideline. (2) [Reserved] (e) Literature references. The following references should be con- sulted for additional background material on this test guideline. (1) Kienitz, H. Methoden der Organischen Chemie ed. Houben-Weyl, Vol. 2, (Georg Thieme Verlag, Stuttgart, 1953, pp. 815-821. (2) Test Guideline 104 for Vapour Pressure Curve, A 80/5 Umweltbundesamt, Berlin (1980). (3) Siwoloboff, A. Berichte-Deutsche Chemische Gesellschaft 19: 795 (1886). (4) Manual of Apparatus FP 5+FP 51, FP 52 and FP 53, Mettler Instrumente AG, CH-8606 Greifensee-Ziirich, Switzerland. (5) European Pharmacopoeia, 1:75 (1974). (6) Organization for Economic Cooperation and Development, Guide- lines for The Testing of Chemicals, OECD 103, Boiling Point/Boiling Range, OECD, Paris, France. (7) ASTM Standard Method E 537-76, Standard Method for Assess- ing the thermal stability of Chemicals by Methods of Differential Thermal Analysis (ASTM Annual Index, latest edition). 11 ------- |