Designation: D 1016 – 99 An American National Standard

Standard Test Method for

Purity of Hydrocarbons from Freezing Points1
This standard is issued under the fixed designation D 1016; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.

1. Scope 3. Summary of Test Method

1.1 This test method covers the sampling and determination 3.1 After measurement of the freezing point of the actual
of purity of essentially pure compounds for which the freezing sample, purity can be calculated from the value of the
points for zero impurity and cryoscopic constants are given. 2 determined freezing point and the values given for the
The compounds to which the test method is applicable are: freezing point for zero impurity and for the applicable
(Warning: Extremely flammable liquids and liquefied gases.) cryoscopic constant or constants.4
n-butane 1,3-butadiene
isobutane isoprene(2-methyl-1,3-butadiene)
3.2 For the equilibrium between an infinitesimal amount of
n-pentane benzene the crystalline phase of the major component and a liquid
isopentane toluene (methylbenzene) phase of the major component and one or more other
n-hexane ethylbenzene
n-heptane o-xylene (1,2-dimethylbenzene)
components, the thermodynamic relation between the
n-octane m-xylene (1,3-dimethylbenzene) temperature of equilib- rium and the composition of the liquid
2,2,4-trimethylpentane p-xylene (1,4-dimethylbenzene) phase is expressed by the equation:5
methylcyclohexane styrene (ethenylbenzene)
isobutene 21n N1 5 21n ~1 2 N2! 5 A~t f 0 2 tf!@1 1 B~t f 0 2 tf! 1 ...#
(1)
1.2 The values stated in SI units are to be regarded as the
standard. The values in parentheses are for information only. where:
1.3 This standard does not purport to address all of the N 1 5 mole fraction of the major component,
safety concerns, if any, associated with its use. It is the N2 5 (1 − N1) 5 sum of the mole fractions of all the
responsibility of the user of this standard to establish appro- other components,
priate safety and health practices and determine the applica- tf 5 freezing point, in degrees Celsius, of the given
bility of regulatory limitations prior to use. For specific hazard substance (in which the mole fraction of the
statements, see Sections 1, 6, 8, and 10-26. major component is N1), defined as the
temperature at which an infinitesimal amount of
NOTE 1—This test method covers systems in which the impurities form crystals of the
with the major component a substantially ideal or sufficiently dilute
solution, and also systems which deviate from the ideal laws, provided major component is in thermodynamic equilibrium
that, in the latter case, the lowering of the freezing point as a function of with the liquid phase (see Note 3 of Test Method
the concentration is known for each most probable impurity in the given D 1015),
substance. tf0 5 freezing point for zero impurity, in degrees Celsius,
for the major component when pure, that is, when
2. Referenced Documents N 1 5 1 or N2 5 0,
2.1 ASTM Standards: A 5 first or main cryoscopic constant, in mole fraction
D 1015 Test Method for Freezing Points of High-Purity per degree, and
Hydrocarbons3 B 5 secondary cryoscopic constant, in mole fraction per
degree.
1
This test method is under the jurisdiction of ASTM Committee D-2 on Neglecting the higher terms not written in the brackets, Eq 1
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee can be transformed to the equation:
D02.04.0D on Physical Methods.
Current edition approved Nov. 10, 1999. Published December 1999. Originally
published as D 1016 – 49 T. Last previous edition D 1016 – 94.
4
2
Numerical constants in this test method were taken from the most recently For a more complete discussion of this test method, see Glasgow, Jr., A. R.,
published data appearing in “Tables of Physical and Thermodynamic Properties of Streiff, A. J., and Rossini, F. D., “Determination of the Purity of Hydrocarbons by
Hydrocarbons and Related Compounds,” or ASTM DS 4A, Physical Constants of Measurement of Freezing Points,” Journal of Research, JRNBA, National Institute
Hydrocarbons C1 to C10, or both, prepared by the American Petroleum Institute, of Standards and Technology, Vol 35, No. 6, 1945, p. 355.
5
Research Project 44. For details, see Taylor, W. J., and Rossini, F. D., “Theoretical Analysis of
3
Annual Book of ASTM Standards, Vol 05.01. Time-Temperature Freezing and Melting Curves as Applied to Hydrocarbons,”
Journal of Research, JRNBA, Nat. Bureau Standards, Vol 32, No. 5, 1944, p. 197;
also Lewis, G. N., and Randall, M., “Thermodynamics and the Free Energy of
Chemical Substances,” 1923, pp. 237, 238, McGraw-Hill Book Co., New York,
NY.

1
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.

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 D 1016
log10 P 5 2.00000 2 ~A / 2.3026!~tf 0 2 tf!@1 1 B~t f 0 2 tf!# 5. Apparatus
(2)
5.1 Sampling Apparatus, as shown in Fig. 1, for withdraw-
where: ing liquefied gases (for example, 1,3-butadiene) from pressure
P 5 purity of the given substance in terms of mole percent storage cylinders.
of the major component. 5.2 Distilling Apparatus, as shown in Fig. 2, for removing
small amounts of polymer from low-boiling compounds (for
4. Significance and Use example, 1,3-butadiene) by simple distillation at atmospheric
4.1 The experimental procedures and physical constants pressure.
provided by this test method, when used in conjunction with 5.3 Distilling Apparatus, as shown in Fig. 3, for removing
Test Method D 1015, allow the determination of the purity of small amounts of polymer from compounds with boiling
the material under test. A knowledge of the purity of these points near room temperature (for example, isoprene) by
hydrocarbons is often needed to help control their manufacture distillation at atmospheric pressure.
and to determine their suitability for use as reagent chemicals 5.4 Vacuum Distilling Apparatus and Transfer Trap, as
or for conversion to other chemical intermediates or finished shown in Fig. 4, for removing dissolved air and large amounts
products.

A—Three-way T stopcock, borosilicate glass (similar to Corning Pyrex No. 7420). B—

Connection to vacuum for purging and for evacuating system CDEGHI. C—Capillary
tube for venting, to which drying tube is also connected.
D—Joint, standard taper, 12/30, borosilicate glass.
E—Condensing tube, borosilicate glass.
F—Dewar flask, 1-qt size, borosilicate glass (similar to American Thermos Bottle Co. No. 8645). G—
Tubing, borosilicate glass, 10 mm in outside diameter, with spherical ground-glass joints, 18/7. H—Tubing,
silicate glass, 10 mm in outside diameter, with spherical ground-glass joints, 18/7.
I—Metal connection, brass spherical male joint at one end fitting to connection to needle valve at other end.
J—Needle valve, brass.
K—Valve on cylinder containing hydrocarbon material. L—
Standard cylinder containing hydrocarbon material. M—Fitting to
connect needle valve J to valve K on cylinder.
FIG. 1 Apparatus for Obtaining Sample

3
 D 1016

C—Dewar vessel, 1-qt capacity, borosilicate glass.

D—Clamp.
E—Distilling tube, borosilicate glass, 25 mm in outside diameter.
F—Standard-taper ground-glass joint, 24/40 borosilicate glass. A—Standard-taper, ground-glass joint, 24/40, borosilicate glass B—
G—Tubing, 10 mm in outside diameter, borosilicate glass. Distilling flask, round bottom, 200-mL capacity, borosilicate glass. C—
H, H8—Spherical ground-glass joints, 18/7, borosilicate glass. Tubing, 10 mm in outside diameter, borosilicate glass.
I—Tubing, 6 mm in outside diameter, borosilicate glass. D, D8—Spherical ground-glass joints, 18/7, borosilicate glass.
J—Receiver, 35 mm in outside diameter, 150 mm in length, borosilicate glass. E—Dewar flask, 1-qt capacity, borosilicate glass.
FIG. 2 Simple Distilling Apparatus for Normally Gaseous F—Receiver, same as J in Fig. 2.
Substances FIG. 3 Simple Distilling Apparatus for Normally Liquid
Substances
of polymer from a compound (for example, 1,3-butadiene or
styrene), by repeated freezing and evacuation, followed by hydrocarbon sample should ever be permitted to cool below
distillation of the compound in vacuum in a closed system. the condensation temperature of oxygen (−183°C at atm). This
would not be likely to occur in normal operation, but might
6. Materials occur if the apparatus were left unattended for some time.
6.1 Carbon Dioxide Refrigerant—Solid carbon dioxide in a
suitable liquid. Acetone is recommended. 7. Procedure
7.1 Measure the freezing point as described in Test Method
NOTE 2—Solid Carbon Dioxide—Warning: Extremely cold
(−78.5°C). Liberates heavy gas which can cause suffocation. Contact D 1015, using the modifications and constants given in Sec-
with skin causes burns or freezing, or both. Vapors can react violently tions 8-26 of this test method for the specific compounds
with hot magnesium or aluminum alloys. Acetone: Warning—Extremely being examined.
flammable. Harmful if inhaled. High concentrations can cause
unconsciousness or death. Contact can cause skin irritation and NOTE 3—The estimated uncertainty in the calculated value of the purity
dermatitis. Use refrigerant bath only with adequate ventilation! as referred to in Sections 8-26 is not equivalent to the precision defined in
RR D-2-1007.
6.2 Liquid Nitrogen or Liquid Air—(Warning: Extremely
cold. Liberates gas which can cause suffocation. Contact with 8. n-Butane6 (Warning: Extremely flammable liquefied gas
skin burns or freezing, or both. Vapors can react violently under pressure. Vapor reduces oxygen available for
with hot magnesium or aluminum alloys.) For use as a breathing.)
refrigerant. If obtainable, liquid nitrogen is preferable because 8.1 Determine the freezing point from freezing curves, with
of its safety. the cage stirrer, with a cooling bath of liquid nitrogen (or
6.2.1 Use liquid nitrogen refrigerant only with adequate liquid air), with a cooling rate of 0.3 to 0.8°C/min for the
ventilation. If liquid air is used as a refrigerant, it is imperative liquid near the freezing point, and with crystallization induced
that any glass vessel containing hydrocarbon or other combus- immedi- ately below the freezing point by means of a cold
tible compound and immersed in liquid air be protected with a rod.
suitable metal shield. The mixing of a hydrocarbon or other
combustible compound with liquid air due to the breaking of a
6
glass container would almost certainly result in a violent For further details, see Glasgow, Jr., A. R., et al. “Determination of Purity by
Measurement of Freezing Points of Compounds Involved in the Production of
explosion. If liquid nitrogen is used as a refrigerant, no Synthetic Rubber,” Analytical Chemistry, ANCHA, Vol 20, 1948, p. 410.
4
 D 1016

A, A8—Standard-taper ground-glass joints, 14/35 borosilicate glass. G and G8—Abestos pad.

B—Tubing, 27 mm in outside diameter, borosilicate glass. H, H8, H9—Stopcock, ground for high vacuum, borosilicate glass.
C, C8—Clamp. I—Spherical ground-glass joint, 18/7, borosilicate glass.
D— Brass cylinder, 273 mm (103⁄4 in.) in length, 28.6 mm (11⁄8 in.) in inside J—Condensing tube, used as trap (see E in Fig. 1).
diameter; for precautions in use of liquid nitrogen and liquid air, see R in K—Connection to vacuum system.
legend to Fig. 1 of Test Method D 1015 and Notes 2 and 3 of Test Method. L, L8—Stopcock, ground for high vacuum, borosilicate glass.
D 1015 M—Standard-taper ground-glass joint, 24/40 borosilicate glass.
D8— Brass cylinder, 254 mm (10 in.) in length, 47.6 mm (1 ⁄8 in.) in inside diameter, N—Receiver withdrawal, 36 mm in outside diameter, borosilicate glass.
7

(see D above). O—Dewar flask, 0.0005-m3(1-pt) capacity, borosilicate glass.

E—Original sample. P—Connection to vacuum.
E8—Distilled sample. Q—Funnel with extension, 4 mm in inside diameter, borosilicate glass.
F, F8—Dewar flask, 0.0009-m3(1-qt) capacity, borosilicate glass. R—Connection to drying tube, borosilicate glass.
FIG. 4 Apparatus for Simple Vacuum Distillation

8.2 The method of obtaining the samples shall be as transfer to the condensing tube (Note 5). Replace the attaching
follows: Assemble the apparatus for obtaining the sample as tubes G and D on the condensing tube by caps. The liquid
shown in Fig. 1, but with no lubricant on the ground-glass sample is now ready for introduction into the freezing tube (O
joints and with the valve at the bottom of the cylinder, so that in Fig. 1 of Test Method D 1015).
sampling is from the liquid phase. Attach to C an absorption
tube containing anhydrous calcium sulfate or other suitable NOTE 5—In case the original sample contained water, there will remain
desiccant (except magnesium perchlorate) so that water is not at I some water that may be discarded after the hydrocarbon portion has
introduced into the system (Note 4). Fill the flask F with the been collected as outlined above.
carbon dioxide refrigerant to within about 51 mm (2 in.) of the 8.5 When the temperature of the platinum thermometer is
top. After about 20 or 30 min, when the system will have near − 80°C, remove the condensing tube (E in Fig. 1) from
cooled sufficiently, remove the absorption tube and begin the the Dewar flask. Wrap a cloth around the upper portion of the
collection of liquid n-butane by opening the valve K and condensing tube (for ease of handling and for preventing the
adjusting the needle valve J so that the sample is collected at refrigerating liquid from contaminating the sample on pour-
a rate of 1 to 2 mL (liquid)/min in the condensing tube E. ing), and after removing the caps on the condensing tube, raise
NOTE 4—However, if some water does condense with the hydrocarbon, the stopper holding the platinum thermometer, and pour the
the freezing point will not be affected significantly because of the sample through the tapered male outlet of the condensing tube
extremely low solubility of water in the hydrocarbon at the freezing point into the freezing tube ( O in Fig. 1 of Test Method D 1015).
of the latter. Quickly replace the stopper holding the platinum thermometer
8.3 Assemble the freezing point apparatus. Place the cool- and start the stirrer, with dry air flowing into the upper portion
ing bath in position around the freezing tube (O in Fig. 1 of of the freezing tube through M (Fig. 1 of Test Method D
Test Method D 1015), letting the temperature as read on the 1015).
platinum thermometer reach about − 80°C when all the sample 8.6 Because the material is normally gaseous at room
has been collected. temperature, care should be taken in disposing of the sample
8.4 When 50 mL of liquid (temperature about − 80°C) has safely.
been collected in the condensing tube, close the valve K (Fig. 8.7 For n-butane, the freezing point for zero impurity, in air
1) and allow the liquid which has collected at I to warm and at 1 atm, is as follows:
tf 0 5 138.362 6 0.025°C (3)
5
 D 1016
and the cryoscopic constants are:
Quickly replace the stopper holding the platinum thermometer
A 5 0.03085 mole fraction/°C and (4)
and start the stirrer, with dry air flowing into the upper portion
B 5 0.0048 mole fraction/°C. (5) of the freezing tube through M (Fig. 1 of Test Method D
8.8 The cryoscopic constants given in 8.7 are applicable to 1015).
samples of n-butane having a purity of about 95 mole % or 9.6 Because of the fact that the material is normally
better, with no one impurity present in an amount that exceeds gaseous at room temperature, care should be taken in
its eutectic composition with the major component. disposing of the sample safely.
8.9 The estimated uncertainty in the calculated value of the 9.7 For isobutane, the freezing point for zero impurity, in
purity is as follows, in mole %: air at 1 atm, is:
tf 0 5 2159.6056 0.025°C (6)
Calculated Purity,
Uncertainty, plus or and the cryoscopic constants are:
mole %
minus, mole % A 5 0.04234 mole fraction/°C and (7)
Over 99.5 0.08
99.0 to 99.5 0.09 B 5 0.0057 mole fraction/°C. (8)
98 to 99 0.10
97 to 98 0.12 9.8 The cryoscopic constants given in 9.7 are applicable to
96 to 97 0.15 samples of isobutane having a purity of about 95 mole % or
95 to 96 0.20
better, with no one impurity present in an amount that exceeds
9. Isobutane6 (Warning: Extremely flammable gas under its eutectic composition with the major component.
pressure. Vapor reduces oxygen available for breathing.) 9.9 The estimated uncertainty in the calculated value of the
9.1 Determine the freezing point from freezing curves with purity is as follows, in mole %:
the cage stirrer, with a cooling bath of liquid nitrogen (or liquid Calculated Purity, Uncertainty, plus or
mole % minus, mole %
air), with a cooling rate of 0.3 to 0.8°C/min for the liquid near Over 99.5 0.10
the freezing point, and with crystallization induced immedi- 99.0 to 99.5 0.11
98 to 99 0.12
ately below the freezing point by means of a cold rod. 97 to 98 0.14
9.2 Obtain the samples as follows: Assemble the apparatus 96 to 97 0.16
for obtaining the sample as shown in Fig. 1, but with no 95 to 96 0.20
lubricant on the ground-glass joints and with the valve at the
bottom of the cylinder, so that sampling is from the liquid 10. n-Pentane (Warning: Extremely flammable liquid.
phase. Attach to C an absorption tube containing anhydrous Harmful if inhaled. Vapors can cause flash fire.)
calcium sulfate or other suitable desiccant (except magnesium 10.1 Determine the freezing point from freezing curves
perchlorate) so that water is not introduced into the system with the cage stirrer, with a cooling bath of liquid nitrogen (or
(Note 4). Fill the flask F with the carbon dioxide refrigerant to liquid air), with a cooling rate of 0.3 to 0.8°C/min for the
within about 51 mm (2 in.) of the top. After about 20 or 30 liquid near the freezing point, and with crystallization induced
min, when the system will have cooled sufficiently, remove immedi- ately below the freezing point by means of a cold
the absorption tube and begin the collection of liquid rod.
isobutane by opening the valve K and adjusting the needle 10.2 To obtain the sample, cool the container and n-pentane
valve J so that the sample is collected at a rate of 1 to 2 mL to near 0°C and transfer a sample of about 60 mL (liquid at the
(liquid)/min in the condensing tube E. given temperature) to a graduated cylinder which has been
9.3 Assemble the freezing point apparatus. Place the cool- kept refrigerated slightly below 0°C. The sample is now ready
ing bath in position around the freezing tube (O in Fig. 1 of for introduction into the freezing tube which should be
Test Method D 1015), letting the temperature as read on the precooled to near − 80°C.
platinum thermometer reach about − 80°C when all the sample 10.3 For n-pentane, the freezing point for zero impurity, in
air at 1 atm, is as follows:
has been collected. tf 5 2129.730 6 0.015°C (9)
9.4 When 50 mL of liquid (temperature about − 80°C) has 0

been collected in the condensing tube, close the valve K (Fig. and the cryoscopic constants are:
1) and allow the liquid which had collected at I to warm and A 5 0.04906 mole fraction/°C and (10)
transfer to the condensing tube (Note 5). Replace the attaching B 5 0.0042 mole fraction/°C. (11)
tubes, G and D, on the condensing tube by caps. The liquid
sample is now ready for introduction into the freezing tube (O 10.4 The cryoscopic constants given in 10.3 are applicable
in Fig. 1 of Test Method D 1015). to samples of n-pentane having a purity of about 95 mole % or
9.5 When the temperature of the platinum thermometer is better, with the usual impurities and with no one impurity
near − 80°C, remove the condensing tube (E in Fig. 1) from present in an amount that exceeds the composition of its
the Dewar flask. Wrap a cloth around the upper portion of the eutectic with the major component.
condensing tube (for ease of handling and for preventing the 10.5 The estimated uncertainty in the calculated value of
refrigerating liquid from contaminating the sample on pour- the purity is as follows, in mole %:
ing), and after removing the caps on the condensing tube, raise Calculated Purity, Uncertainty, plus or
the stopper holding the platinum thermometer, and pour the mole % minus, mole %

6
 D 1016
sample through the tapered male outlet of the condensing tube Over 99.5 0.07
99.0 to 99.5 0.08
into the freezing tube ( O in Fig. 1 of Test Method D 1015). 98 to 99 0.09

7
 D 1016
97 to 98 0.10
96 to 97 0.12 B 5 0.0039 mole fraction/°C. (17)
95 to 96 0.14
12.4 The cryoscopic constants given in 12.3 are applicable
11. Isopentane (Warning: Extremely flammable liquid. to samples of n-hexane having a purity of about 95 mole % or
Harmful if inhaled. Vapors can cause flash fire.) better, with the usual impurities and with no one impurity
11.1 Determine the freezing point from melting curves with present in an amount that exceeds the composition of its
the double helix stirrer, with a cooling bath of liquid nitrogen eutectic with the major component.
(or liquid air) to obtain the slurry of crystals and liquid, and a 12.5 The estimated uncertainty in the calculated value of
the purity is as follows, in mole %:
warming bath of carbon dioxide refrigerant, with a cooling rate Calculated Purity, Uncertainty, plus or
mole % minus, mole %
of 0.3 to 0.8°C/min for the liquid near the freezing point and Over 99.5 0.05
with crystallization induced immediately below the freezing 99.0 to 99.5 0.06
point, by seeding with crystals. (Crystallization may also be 98 to 99 0.07
97 to 98 0.08
induced with a cold rod, but the recovery from undercooling 96 to 97 0.10
will not be as rapid.) 95 to 96 0.12
11.2 To obtain a sample, cool the container and isopentane 13. n-Heptane (Warning: Flammable. Harmful if inhaled.)
to near 0°C and transfer a sample of about 65 mL (liquid at the
13.1 Determining the freezing point from freezing curves
given temperature) to a graduated cylinder which has been
kept refrigerated slightly below 0°C. The sample is now ready with the cage stirrer, with a cooling bath of liquid nitrogen (or
liquid air), with a cooling rate of 0.3 to 0.8°C/min for the
for introduction into the freezing tube which should be
liquid near the freezing point, and with crystallization induced
precooled to near − 80°C.
immediately below the freezing point by means of a cold rod.
11.3 For isopentane, the freezing point for zero impurity, in
13.2 Obtain a sample of 50 mL (measured at room
air at 1 atm, is as follows:
tempera- ture) directly from its original container by means of
tf 0 5 2159.9056 0.015° C (12) a pipet or by pouring into a graduated cylinder.
and the cryoscopic constants are: 13.3 For n-heptane, the freezing point for zero impurity, in
A 5 0.04829 mole fraction/°C and (13) air at 1 atm, is:
B 5 0.0058 mole fraction/°C. (14) tf 0 5 290.5816 0.010°C (18)
11.4 The cryoscopic constants given in 9.3 are applicable to and the cryoscopic constants are:
samples of isopentane having a purity of about 95 mole % or A 5 0.05065 mole fraction/°C and (19)
better, with the usual impurities and with no one impurity B 5 0.0033 mole fraction/°C. (20)
present in an amount which exceeds the composition of the 13.4 The cryoscopic constants given in 13.3 are applicable
eutectic with the major component. to samples of n-heptane having a purity of about 95 mole % or
11.5 The estimated uncertainty in the calculated value of better, with the usual impurities and with no one impurity
the purity is as follows, in mole %: present in an amount that exceeds the composition of its
Calculated Purity, Uncertainty, plus or
mole % minus, mole % eutectic with the major component.
Over 99.5 0.07 13.5 The estimated uncertainty in the calculated value of
99.0 to 99.5 0.08
98 to 99 0.09 the purity is as follows, in mole %:
97 to 98 0.10 Calculated Purity, Uncertainty, plus or minus,
96 to 97 0.12 mole % mole %
95 to 96 0.14 Over 99.5 0.05
99.0 to 99.5 0.06
12. n-Hexane (Warning: Extremely flammable. Harmful if 98 to 99 0.07
97 to 98 0.08
inhaled. Can produce nerve cell damage. Vapors can 96 to 97 0.10
cause flash fire.) 95 to 96 0.12
12.1 Determine the freezing point from freezing curves 14. n-Octane (Warning: Flammable. Harmful if inhaled.)
with the cage stirrer, with a cooling bath of liquid nitrogen (or 14.1 Determine the freezing point from freezing curves
liquid air), with a cooling rate of 0.3 to 0.8°C/min for the with the cage stirrer, with a cooling bath of carbon dioxide
liquid near the freezing point and with crystallization induced refrig- erant at a cooling rate of 0.3 to 0.8°C/min for the liquid
immediately below the freezing point by means of a cold rod. near the freezing point, and with crystallization induced
12.2 Obtain a sample of 50 mL (measured at room immediately below the freezing point by means of a cold rod.
tempera- ture) directly from its original container by means of 14.2 Obtain a sample of 50 mL (measured at room
a pipet or by pouring into a graduated cylinder. tempera- ture) directly from its original container by means of
12.3 For n-hexane, the freezing point for zero impurity, in a pipet or by pouring into a graduated cylinder.
air at 1 atm, is as follows: 14.3 For n-octane the freezing point for zero impurity, in
tf 0 5 295.3226 0.010°C (15) air at 1 atm, is as follows:
and the cryoscopic constants are: tf 0 5 256.7646 0.010°C (21)
A 5 0.04956 mole fraction/°C and (16) and the cryoscopic constants are:
8
 D 1016
A 5 0.05329 mole fraction/°C and (22)
B 5 0.0031 mole fraction/°C. (23) 16. Methylcyclohexane (Warning: Flammable. Harmful if
inhaled.)
14.4 The cryoscopic constants given in 14.3 are applicable 16.1 Determine the freezing point from melting curves with
to samples of n-octane having a purity of about 95 mole % or the double helix stirrer, with a cooling bath of liquid nitrogen
better, with the usual impurities and with no impurity present (or liquid air) to obtain the slurry of crystals and liquid, and a
in an amount that exceeds the composition of its eutectic with warming bath of carbon dioxide refrigerant, with a cooling
the major component. rate of 0.3 to 0.8°C/min for the liquid near the freezing point
14.5 The estimated uncertainty in the calculated value of and with crystallization induced immediately below the
the purity is as follows, in mole %: freezing point by seeding with crystals. (Crystallization may
also be induced with a cold rod, but the recovery from
undercooling
Calculated Purity, Uncertainty, plus or minus,
mole % mole %
will not be as rapid.)
Over 99.5 0.05 16.2 Obtain a sample of 60 mL (measured at room tempera-
99.0 to 99.5 0.06 ture) directly from the original container by pouring into a
98 to 99 0.07
97 to 98 0.08 graduated cylinder.
96 to 97 0.10 16.3 For methylcyclohexane, the freezing point for zero
95 to 96 0.12
impurity, in air at 1 atm, is as follows:
15. 2,2,4-Trimethylpentane (Warning: Extremely tf 0 5 2126.5966 0.015°C (27)
flammable. Harmful if inhaled. Vapors can cause flash and the cryoscopic constants are:
fire.) A 5 0.03779 mole fraction/°C and (28)
15.1 For samples having a purity greater than about 99.5 A 5 0.0032 mole fraction/°C. (29)
mole %, determine the freezing point from melting curves
16.4 The cryoscopic constants given in 16.3 are applicable
with the cage stirrer, with a cooling bath of liquid nitrogen (or
to samples of methylcyclohexane having a purity of about 95
liquid air), and a warming bath of solid carbon dioxide
mole % or better, with the usual impurities and with no one
refrigerant, with a cooling rate of 0.3 to 0.8°C/min for the
impurity present in an amount that exceeds the composition of
liquid near the freezing point and with crystallization induced
the eutectic with the major component.
immediately below the freezing point by means of a cold rod.
15.2 For samples having a purity less than about 99.5 16.5 The estimated uncertainty in the calculated value of
mole %, determine the freezing point from freezing curves the purity is as follows, in mole %:
Calculated Purity, Uncertainty, plus or
with the cage stirrer, with a cooling bath of liquid nitrogen (or mole % minus, mole %
liquid air), with a cooling rate of 0.3 to 0.8°C/min for the Over 99.5 0.05
99.0 to 99.5 0.06
liquid near the freezing point, and with crystallization induced 98 to 99 0.07
immediately below the freezing point by means of a cold rod. 97 to 98 0.08
15.3 Obtain a sample of 50 mL (measured at room 96 to 97 0.10
95 to 96 0.12
tempera- ture) directly from its original container by means of
pipet or by pouring into a graduated cylinder. 17. Isobutene6 (Warning: Extremely flammable liquefied
15.4 For 2,2,4-trimethylpentane, the freezing point for zero gas under pressure. Vapor reduces oxygen available for
impurity, in air at 1 atm, is as follows: breathing.)
tf 0 5 2107.3736 0.010°C (24) 17.1 Determine the freezing point from freezing curves,
and the cryoscopic constants are: with the cage stirrer, with a cooling bath of liquid nitrogen (or
liquid air), with a cooling rate of 0.3 to 0.8°C/min for the
A 5 0.04032 mole fraction/°C and (25)
liquid near the freezing point, and with crystallization induced
B 5 0.0043 mole fraction/°C. (26) immediately below the freezing point by means of a cold rod.
15.5 The cryoscopic constants given in 15.4 are applicable 17.2 Obtain the samples as follows: Assemble the
to samples of 2,2,4-trimethylpentane having a purity of about apparatus for obtaining the sample as shown in Fig. 1, but
95 mole % or better, with the usual impurities and with no one with no lubricant on the ground-glass joints and with the valve
impurity present in an amount that exceeds the composition of at the bottom of the cylinder, so that sampling is from the
its eutectic with the major component. liquid phase. Attach to C an absorption tube containing
anhydrous calcium sulfate or other suitable desiccant (except
15.6 The estimated uncertainty in the calculated value of
magnesium perchlorate) so that water is not introduced into
the purity is as follows, in mole %:
the system (Note 4). Fill the flask F with the carbon dioxide
refrigerant to
Calculated Purity, Uncertainty, plus or
mole % minus, mole % within about 51 mm (2 in.) of the top. After about 20 or 30 min,
Over 99.5 0.05 96 to 97 0.10
99.0 to 99.5 0.06 95 to 96 0.12
98 to 99 0.07
97 to 98 0.08
9
 D 1016
when the system will have cooled
sufficiently, remove the absorption tube and
begin the collection of liquid isobutene by
opening the valve K and adjusting the needle
valve J so that the sample is collected at a
rate of 1 to 2 mL (liquid)/min in the
condensing tube E.

10
 D 1016
17.3 Assemble the freezing point apparatus. Place the cool-
ing bath in position around the freezing tube (O in Fig. 1 of lubricant on the ground-glass joints and with the valve at the
Test Method D 1015), letting the temperature as read on the bottom of the cylinder, so that sampling is from the liquid
platinum thermometer reach about − 80°C when all the sample phase. Attach to C an absorption tube containing anhydrous
has been collected. calcium sulfate or other suitable desiccant (except magnesium
17.4 When 50 mL of liquid (temperature about − 80°C) has perchlorate) so that water is not introduced into the system
been collected in the condensing tube, close the valve K (Fig. (Note 4). Fill the flask F with the carbon dioxide refrigerant to
1) and allow the liquid which has collected at I to warm and within about 51 mm (2 in.) of the top. After about 20 or 30
transfer to the condensing tube (Note 5). Replace the attaching min, when the system will have cooled sufficiently, remove
tubes G and D on the condensing tube by caps. The liquid the absorption tube and begin the collection of liquid 1,3-
sample is now ready for introduction into the freezing tube (O butadiene by opening the valve K and adjusting the needle
in Fig. 1 of Test Method D 1015). valve J so that the sample is collected at a rate of 1 to 2 mL
17.5 When the temperature of the platinum thermometer is (liquid)/min in the condensing tube E.
near − 80°C, remove the condensing tube (E in Fig. 1) from 18.3 Assemble the freezing point apparatus. Place the cool-
the Dewar flask. Wrap a cloth around the upper portion of the ing bath in position around the freezing tube (O in Fig. 1 of
condensing tube (for ease of handling and for preventing the Test Method D 1015), letting the temperature as read on the
refrigerating liquid from contaminating the sample on pour- platinum thermometer reach about − 80°C when all the sample
ing), and after removing the caps on the condensing tube, raise has been collected.
the stopper holding the platinum thermometer, and pour the 18.4 When 50 mL of liquid (temperature about − 80°C) has
sample through the tapered male outlet of the condensing tube been collected in the condensing tube, close the valve K (Fig.
into the freezing tube ( O in Fig. 1 of Test Method D 1015). 1) and allow the liquid which has collected at I to warm and
Quickly replace the stopper holding the platinum thermometer transfer to the condensing tube (Note 5). Replace the attaching
and start the stirrer, with dry air flowing into the upper portion tubes G and D on the condensing tube by caps. The liquid
of the freezing tube through M (Fig. 1 of Test Method D sample is now ready for introduction into the freezing tube (O
1015). in Fig. 1 of Test Method D 1015).
17.6 Because of the fact that the material is normally 18.5 In some cases, it will be desirable to remove the
gaseous at room temperature, care should be taken in dimer, other C8 hydrocarbons, and higher polymer from the
disposing of the sample safely. sample of 1,3-butadiene before determining the purity. For
17.7 For isobutene, the freezing point for zero impurity, in this removal, the procedure is as follows: Assemble the
air at 1 atm, is as follows: apparatus shown in Fig. 2 with a small amount (10 to 100
tf 0 5 2140.3376 0.020° C (30) ppm) of tertiary butyl catechol or other suitable inhibitor
and the cryoscopic constants are: placed in the bottom of the distilling tube E, with no lubricant
A 5 0.04044 mole fraction/°C and (31)
on the ground-glass joints. It is also desirable to place at the
bottom of the flask a piece of carborundum or other suitable
B 5 0.005 mole fraction/°C. (32)
material to prevent bumping. Make a connection to the
17.8 The cryoscopic constants given in 17.7 are applicable atmosphere through an absorption tube (as previously
to samples of isobutene having a purity of about 95 mole % or described in this section) at H8 so that entering air is freed of
better, with no one impurity present in an amount that exceeds carbon dioxide and water. Place a bath containing carbon
its eutectic composition with the major component. dioxide refrigerant around the distilling tube E, and also
17.9 The estimated uncertainty in the calculated value of around the receiver J so that the small entrance and exit tubes
the purity is as follows, in mole %: of J are covered with at least 5 cm of the bath. After about 20
to 30 min, when the system will have precooled
Calculated Purity, Uncertainty, plus or sufficiently, disconnect the connection to the atmosphere at H8,
mole % minus, mole % remove the cap F and introduce the liquid butadiene (tempera-
Over 99.5 0.08 apparatus for obtaining the sample as shown in Fig. 1, but
99.0 to 99.5 0.09
98 to 99 0.10 with no
97 to 98 0.12
96 to 97 0.15
95 to 96 0.20

18. 1,3-Butadiene6 (Warning: Extremely flammable

liquefied gas under pressure. May form explosive
peroxides upon exposure to air. Harmful if inhaled.
Irritating to eyes, skin, and mucous membranes.)
18.1 Determine the freezing point from freezing curves
with the cage stirrer, with a cooling bath of liquid nitrogen (or
liquid air), with a cooling rate of 0.3 to 0.8°C/min for the
liquid near the freezing point and with crystallization induced
immediately below the freezing point by means of a cold rod.
18.2 Obtain the samples as follows: Assemble the
11
 D 1016
ture near − 80°C) by pouring through a precooled funnel
(such as Q in Fig. 4 which may be cooled without
contamination by liquid air or liquid nitrogen) into the
distilling tube. Grease the cap F and replace immediately
after the introduction of the sample. Then distill the material
by removing the bath from the distilling tube and allowing it
to warm in contact with the air of the room. Distillation is
complete when the distilling tube has warmed to room
temperature. Disconnect the receiver with the bath around it,
cap it at H and H8, and transfer 50 mL (liquid at about −
80°C) of the liquid butadiene to the freezing tube by pouring
through I in a manner similar to that described for a sample
collected in the condensing tube.
18.6 When the temperature of the platinum thermometer is
near − 80°C, remove the condensing tube (E in Fig. 1) or the
receiver ( J in Fig. 2) from the Dewar. Wrap a cloth around
the upper portion of the condensing tube or receiver (for
ease of

12
 D 1016
handling and for preventing the refrigerating liquid from
contaminating the sample on pouring), and after removing the ing B to a vacuum line. After evacuation, close the stopcock A
caps on the condensing tube or receiver, raise the stopper to the outlets B and C, and collect the sample of isoprene (55
holding the platinum thermometer, and pour the sample mL, liquid, at about − 80°C) in the refrigerated condensing
through the tapered male outlet of the condensing tube or the tube E, in which was previously placed a small amount (about
exit tube I of the receiver into the freezing tube (O in Fig. 1 of 10 to 100 ppm) of tertiary butyl catechol or other suitable
Test Method D 1015). Quickly replace the stopper holding the inhibitor. The sample as thus collected will contain the bulk of
platinum thermometer and start the stirrer, with dry air any dimer present in the original material. The sample,
flowing into the upper portion of the freezing tube through M including substantially all of the dimer, is now ready for
(Fig. 1 of Test Method D 1015). introduction into the freezing tube, which should be precooled
18.7 Because of the fact that the material is normally to near − 100°C. When the isoprene is contained in capped
gaseous at room temperature, care should be taken in bottles or sealed ampoules, cool the container and isoprene to
disposing of the sample safely. near 0°C and transfer a sample of about 65 mL (liquid at the
18.8 For 1,3-butadiene, the freezing point for zero given temperature) to a graduated cylinder which has been
impurity, in air at 1 atm, is kept refrigerated slightly below 0°C. The sample, including
such amount of dimer and higher polymer as was originally
tf 0 5 2108.9026 0.010° C (33)
present, is now ready for introduction into the freezing tube,
and the cryoscopic constants are: which should be precooled to near − 100°C.
A 5 0.03560 mole fraction/°C and (34) 19.4 In most cases it will be desirable to remove the dimer
B 5 0.0053 mole fraction/°C. (35) and higher polymer from the sample of isoprene before
18.9 The cryoscopic constants given in 18.8 are applicable determining the purity. For this removal, the procedure is as
to samples of 1,3-butadiene having a purity of about 95 mole follows: Assemble the apparatus shown in Fig. 3 with no
% or better, with no one impurity present in an amount that lubricant on the ground-glass joints D and D8. Place a small
exceeds its eutectic composition with the major component. amount of tertiary butyl catechol or other suitable inhibitor
18.10 The estimated uncertainty in the calculated value of (about 10 to 100 ppm) in the receiver F and a larger amount
the purity is as follows, in mole %: (about 100 to 1000 ppm) in the distilling flask B. It is also
desirable to place at the bottom of the flask B a piece of
Calculated Purity, mole % carborundum or other suitable material to prevent bumping.
Uncertainty, plus or minus, mole %
Place a cooling bath of water-ice around the distilling flask B
Over 99.5 0.05
99.0 to 99.5 0.06 and a bath containing carbon dioxide refrigerant around the
98 to 99 0.07 receiver F. Make a connection to the atmosphere at D8
97 to 98 0.08 through which the air is first freed of carbon dioxide and
96 to 97 0.09
95 to 96 0.10 water, using a tube containing Ascarite and anhydrous
calcium sulfate or other suitable desiccant. Introduce the
sample (at 0°C) into the
19. Isoprene (2-Methyl-1,3-Butadiene)6 (Warning: system by connecting, through heavy-walled tubing, the open-
Extremely flammable liquefied gas under pressure. Vapor
reduces oxygen available for breathing.)
19.1 For samples having a purity greater than about 98
mole %, determine the freezing point from melting curves,
with the double helical stirrer, with a cooling bath of liquid
nitrogen (or liquid air), and a warming bath of carbon dioxide
refrigerant, with the jacket of the freezing tube open to the
high vacuum system during the entire melting part of the
curve, with a cooling rate of 0.3 to 0.8°C/min for the liquid
near the freezing point and with crystallization induced
immediately below the freezing point by means of a cold rod.
19.2 For samples having a purity less than about 98 mole
%, determine the freezing point from freezing curves, with
either the aluminum cage stirrer or the double helical stirrer,
with a cooling bath of liquid nitrogen (or liquid air), with a
cooling rate of 0.3 to 0.8°C/min for the liquid near the
freezing point and with crystallization induced immediately
below the freez- ing point by means of a cold rod.
19.3 The method of obtaining the sample is as follows:
When the material is in a cylinder, assemble the apparatus
shown in Fig. 1, with a suitable lubricant on the ground-glass
joints, and with the valve below the body of the cylinder so
that the sample is obtained from the liquid phase. Evacuate the
13
 D 1016
flask B, place the cap A in position with a suitable lubricant
between the grindings, and remove the connection to the
atmosphere at D8. Place a water bath (at 40 to 50°C) around
the flask B and distill the material into F. Stop the distillation
when a small residue remains in B with the water bath at
50°C. Detach the receiver F at D and cap at D and D8 with
the bath containing carbon dioxide refrigerant still
surrounding it. Remove the sample, with the upper portion of
the container wrapped with a cloth (for ease of handling and
for preventing the refrigerating liquid from contaminating the
sample on pouring), from the flask E, remove the caps and
introduce the sample into the freezing tube, previously
precooled to near − 100°C, by pouring through D8. For the
procedure for introducing the sample into the tube, see 18.6
on 1,3-butadiene.
19.5 If the sample contains a very large amount of dimer
and polymer, then the simple preceding procedure outlined
will not suffice because the required distilling temperature
will be too high, and a more complicated procedure is used,
as follows: Assemble the apparatus shown in Fig. 4, with
inhibitor placed in the distilling tube and receiver (plus some
carborundum in the distilling tube to prevent bumping) as
previously described in 19.4, and with all the ground joints
except that at A lubricated. Place a cooling bath of carbon
dioxide refrigerant around the distilling tube E. Permit air,
freed of carbon dioxide and water, to enter the system
through RH9 H8H in order to

14
 D 1016
compensate for the change in volume. When the sample is
cooled, remove the cap A and introduce the sample through the freezing point and with crystallization induced
the funnel Q, which has been precooled with liquid air or immediately below the freezing point by means of a cold rod.
liquid nitrogen. Then lubricate the cap A and close the 20.2 Obtain a sample of 50 mL (measured at room tempera-
stopcocks H, H8, and H9. Place liquid air or liquid nitrogen ture) directly from the original container by means of a pipet
around the condensing tube E (Fig. 1), which serves as a trap, or by pouring into a graduated cylinder. Then filter the sample
and also replace the carbon dioxide refrigerant around the directly into the freezing point tube (O in Fig. 1 of Test
distilling tube E (Fig. 4) with liquid nitrogen or liquid air. Method D 1015), through silica gel to remove water. See 9.3,
After the isoprene has solidified, evacuate the system by and Fig. 5 of Test Method D 1015.
opening H and H8 to the vacuum system. Close the stopcocks 20.3 For benzene, the freezing point for zero impurity, in
H and H8 and remove the bath from E to allow the material to air at 1 atm, is:
melt and release dissolved air. Crystallize the material again tf 0 5 25.5316 0.010°C (39)
and evacuate the system as before. Repeat the process again, if and the cryoscopic constants are:
necessary, to remove substantially all the air. (If any
A 5 0.01523 mole fraction/°C and (40)
hydrocarbon has been caught in the trap J, it should be
distilled back into the tube E, with the stopcock H open and B 5 0.0032 mole fraction/°C. (41)
H8 closed.) Distill the material into E8 by placing carbon 20.4 The cryoscopic constants given in 20.3 are applicable
dioxide refrigerant around the receiver and a water-ice bath to samples of benzene having a purity of about 95 mole % or
around E (after the latter has warmed to near 0°C). Halt the better, with the usual impurities and with no one impurity
distillation when the transfer of material into the receiver has present in an amount that exceeds the composition of its
substantially halted, by admitting air (freed of water and eutectic with the major component.
carbon dioxide) into the system through RH9 H8H. Remove 20.5 The estimated uncertainty in the calculated value of
the sample from the receiving tube E with the withdrawal the purity is as follows, in mole %:
receiver N. Evacuate the system LMNL, with L8
Calculated Purity, Uncertainty, plus or
open and L closed, through P and then close the stopcock L8. mole % minus, mole %
Surround the receiver N8 by carbon dioxide refrigerant. Re- Over 99.5 0.02
99.0 to 99.5 0.03
move the material by inserting the inlet tube at L into the 98 to 99 0.04
receiver and then opening the stopcock L. This procedure 97 to 98 0.05
avoids loss by evaporation. Then introduce the material into 96 to 97 0.06
95 to 96 0.08
the freezing tube, previously precooled to near − 100°C, by
pouring through the tapered joint at M. For the procedure for
21. Toluene (Warning: Flammable. Vapor harmful.)
introducing the sample into the tube, see 18.6 on 1,3-
butadiene. 21.1 Determine the freezing point from freezing curves
19.6 For isoprene (2-methyl-1,3-butadiene), the freezing with the cage stirrer, with a cooling bath of liquid nitrogen (or
point for zero impurity, in air at 1 atm, is: liquid air), with a cooling rate of 0.3 to 0.8°C/min for the
liquid near the freezing point, and with crystallization induced
tf 0 5 2145.9646 0.020°C (36)
immedi- ately below the freezing point by means of a cold
and the cryoscopic constants are: rod.
A 5 0.0330 mole fraction/°C and (37) 21.2 A sample of 50 mL (measured at room temperature) is
B 5 0.0030 mole fraction/°C. (38) obtained directly from its original container by means of a
pipet or by pouring into a graduated cylinder.
19.7 The cryoscopic constants given in 19.6 are applicable 21.3 For toluene, the freezing point for zero impurity, in air
to samples of isoprene having a purity of about 95 mole % or at 1 atm, is:
better, with no one impurity present in an amount that exceeds
the eutectic composition with the major component. tf 5 294.9656 0.012°C (42)
0

19.8 The estimated uncertainty in the calculated value of and the cryoscopic constants are:
the purity is as follows, in mole %: A 5 0.02508 mole fraction/°C and (43)
Calculated Purity, mole % Uncertainty, plus or minus, mole % B 5 0.0019 mole fraction/°C. (44)
Over 99.5 0.08 21.4 The cryoscopic constants given in 21.3 are applicable
99.0 to 99.5 0.10
98 to 99 0.12
to samples of toluene having a purity of about 95 mole % or
97 to 98 0.15 better, with the usual impurities and with no one impurity
96 to 97 0.20 present in an amount that exceeds the composition of its
95 to 96 0.25
eutectic with the major component.
20. Benzene (Warning: Poison. Carcinogen. Harmful or 21.5 The estimated uncertainty in the calculated value of
fatal if swallowed. Extremely flammable. Vapors can the purity is as follows, in mole %:
cause flash fire. Vapor harmful, can be absorbed through Calculated Purity, Uncertainty, plus or
mole % minus, mole %
skin.) with the cage stirrer, with a cooling bath of carbon
20.1 Determine the freezing point from freezing curves dioxide refrig- erant, with a cooling rate of 0.3 to
15
 D 1016
0.8°C/min for the liquid near Over 99.5 0.03
99.0 to 99.5 0.04
98 to 99 0.05
97 to 98 0.06
96 to 97 0.08

16
 D 1016
95 to 96 0.10
eutectic with the major component.
22. Ethylbenzene (Warning: Flammable. Vapor harmful.) 23.5 The estimated uncertainty in the calculated value of the
purity is as follows, in mole %:
22.1 Determine the freezing point from melting curves with Calculated Purity, Uncertainty, plus or
the cage stirrer, with a cooling bath of liquid nitrogen (or mole % minus, mole %
liquid air) to obtain the slurry of crystals and liquid, and a
Over 99.5 0.02
warming bath of carbon dioxide refrigerant, with a cooling 99.0 to 99.5 0.03
rate of 0.3 to 0.8°C/min for the liquid near the freezing point, 98 to 99 0.04
and with crystallization induced immediately below the 97 to 98 0.05
96 to 97 0.06
freezing point by seeding with crystals. (Crystallization may 95 to 96 0.08
also be induced
with a cold rod, but the recovery from undercooling will not be 24. m-Xylene (Warning: Flammable. Vapor harmful.)
as rapid.) 24.1 Determine the freezing point from freezing curves
22.2 Obtain a sample of 50 mL (measured at room with the cage stirrer, with a cooling bath of solid carbon
tempera- ture) directly from its original container by means of dioxide refrigerant, with a cooling rate of 0.3 to 0.8°C/min for
a pipet or by pouring into a graduated cylinder. the liquid near the freezing point, and with crystallization
22.3 For ethylbenzene, the freezing point for zero impurity, induced immediately below the freezing point by seeding with
in air at 1 atm, is: crystals. (Crystallization may also be induced with a cold rod,
tf 0 5 294.9496 0.015°C (45) but the recovery from undercooling will not be as rapid.)
and the cryoscopic constants are: 24.2 Obtain a sample of 50 mL (measured at room
tempera- ture) directly from its original container by means of
A 5 0.03471 mole fraction/°C and (46)
a pipet or by pouring into a graduated cylinder.
B 5 0.0029 mole fraction/°C. (47) 24.3 For m-xylene, the freezing point for zero impurity, in
22.4 The cryoscopic constants given in 22.3 are applicable air at 1 atm, is:
to samples of ethylbenzene having a purity of about 95 mole tf 0 5 247.8446 0.020°C (51)
% or better, with the usual impurities and with no one
and the cryoscopic constants are:
impurity present in an amount that exceeds the composition of
its eutectic with the major component. A 5 0.02741 mole fraction/°C and (52)
22.5 The estimated uncertainty in the calculated value of B 5 0.0027 mole fraction/°C. (53)
the purity is as follows, in mole %: 24.4 The cryoscopic constants given in 24.3 are applicable
Calculated Purity, Uncertainty, plus or to samples of m-xylene having a purity of about 95 mole % or
mole % minus, mole %
Over 99.5 0.05
better, with the usual impurities and with no one impurity
99.0 to 99.5 0.06 present in an amount that exceeds the composition of its
98 to 99 0.08 eutectic with the major component.
97 to 98 0.10
96 to 97 0.12 24.5 The estimated uncertainty in the calculated value of
95 to 96 0.14 the purity is as follows, in mole %:
23. o-Xylene (Warning: Flammable. Vapor harmful.) Calculated Purity, Uncertainty, plus or
mole % minus, mole %
23.1 The freezing point is determined from freezing curves better, with the usual impurities and with no one impurity
with the cage stirrer, with a cooling bath of carbon dioxide present in an amount that exceeds the composition of its
refrigerant, with a cooling rate of 0.3 to 0.8°C/min for the
liquid near the freezing point, and with crystallization induced
immediately below the freezing point by seeding with crystals.
(Crystallization may also be induced with a cold rod, but the
recovery from undercooling will not be as rapid.)
23.2 A sample of 50 mL (measured at room temperature) is
obtained directly from its original container by means of a
pipet or by pouring into a graduated cylinder.
23.3 For o-xylene, the freezing point for zero impurity, in
air at 1 atm, is:
tf 0 5 225.1676 0.005°C (48)
and the cryoscopic constants are:
A 5 0.02659 mole fraction/°C and (49)
B 5 0.0030 mole fraction/°C. (50)
23.4 The cryoscopic constants given in 23.3 are applicable
to samples of o-xylene having a purity of about 95 mole % or
17
 D 1016
Over 99.5 0.05
99.0 to 99.5 0.06
98 to 99 0.07
97 to 98 0.08
96 to 97 0.10
95 to 96 0.12

25. p-Xylene (Warning: Flammable. Vapor harmful.)

25.1 Determine the freezing point from freezing curves
with the cage stirrer, with a cooling bath of carbon dioxide
refrig- erant, with a cooling rate of 0.3 to 0.8°C/min for the
liquid near the freezing point, and with crystallization
induced immedi- ately below the freezing point, by seeding
with crystals. (Crystallization may also be induced with a
cold rod, but the recovery from undercooling will not be as
rapid.)
25.2 Obtain a sample of 50 mL (measured at room
tempera- ture) directly from the original container by means
of a pipet or by pouring into a graduated cylinder. The
sample is then filtered directly into the freezing point tube,
(O in Fig. 1 of Test Method D 1015), through silica gel to
remove water. See 9.3 and Fig. 5 of Test Method D 1015.
25.3 For p-xylene, the freezing point for zero impurity, in
air at 1 atm, is:

18
 D 1016
tf 0 5 213.258 6 0.012°C (54)
and the cryoscopic constants are: sample is distilled at room temperature.
26.4 For styrene, the freezing point for zero impurity, in air
A 5 0.02509 mole fraction/°C and (55)
at 1 atm, is:
B 5 0.0028 mole fraction/°C. (56)
tf 0 5 230.6106 0.008°C (57)
25.4 The cryoscopic constants given in 25.3 are applicable and the cryoscopic constants are:
to samples of p-xylene having a purity of about 95 mole % or
better, with the usual impurities and with no one impurity A 5 0.02365 mole fraction/°C and (58)
present in an amount that exceeds the composition of its B 5 0.0044 mole fraction/°C. (59)
eutectic with the major component. 26.5 The cryoscopic constants given in 26.4 are applicable
25.5 The estimated uncertainty in the calculated value of to samples of styrene having a purity of not less than about 95
the purity is as follows, in mole %: mole %, with the usual impurities and with no one impurity
present in an amount that exceeds the composition of its
Calculated Purity, Uncertainty, plus or
mole % minus, mole %
eutectic with the main component.
Over 99.5 0.03
26.6 The estimated uncertainty in the calculated value of
99.0 to 99.5 0.04 the purity is as follows, in mole %:
98 tomole
Calculated Purity, 99 % 0.05
97 to 98 0.06 Uncertainty, plus or minus, mole %
96 to 97 0.08
95 to 96 0.10 Over 99.5 0.04
99.0 to 99.5 0.05
26. Styrene (Ethenylbenzene)6 (Warning: Flammable. 98 to 99 0.06
97 to 98 0.07
Vapor harmful.) 96 to 97 0.08
26.1 Determine the freezing point from freezing curves 95 to 96 0.09
with the cage stirrer, with cooling bath of carbon dioxide
refrigerant, with a cooling rate of 0.3 to 0.8°C/min for the 27. Precision and Bias
liquid near the freezing point, and with crystallization induced 27.1 Precision—The precision for this test method is gov-
immediately below the freezing point by means of a cold rod. erned by the precision of Test Method D 1015. Test Method
26.2 Obtain a sample of 50 mL (measured at room D 1015 must be used for the freezing point determinations in
tempera- ture) directly from the original container by means of this test method.
a pipet or by pouring into a graduated cylinder. 27.2 Bias—The bias for this test method is governed by the
26.3 If the previous treatment or storage condition of bias of Test Method D 1015. Test Method D 1015 must be
material was such that dimerization or polymerization may used for the freezing point determinations in this test method.
have occurred, the dimer or polymer should be removed by a
simple vacuum distillation (Fig. 4), using the same procedure 28. Keywords
as described under isoprene (see 19.5) except that carbon 28.1 crystallization; freeze point; LPG; pure hydrocarbons;
dioxide refrigerant is used to refrigerate the receiver and the purity

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