ASTM D2766-95(2005)
(Test Method)Standard Test Method for Specific Heat of Liquids and Solids
Standard Test Method for Specific Heat of Liquids and Solids
SIGNIFICANCE AND USE
The specific heat or heat capacity of a substance is a thermodynamic property that is a measure of the amount of energy required to produce a given temperature change within a unit quantity of that substance. It is used in engineering calculations that relate to the manner in which a given system may react to thermal stresses.
SCOPE
1.1 This test method covers the determination of the heat capacity of liquids and solids. It is applicable to liquids and solids that are chemically compatible with stainless steel, that have a vapor pressure less than 13.3 kPa (100 torr), and that do not undergo phase transformation throughout the range of test temperatures. The specific heat of materials with higher vapor pressures can be determined if their vapor pressures are known throughout the range of test temperatures.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D2766 – 95 (Reapproved 2005)
Standard Test Method for
Specific Heat of Liquids and Solids
This standard is issued under the fixed designation D2766; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope
T = temperature of hot zone, °C,
1.1 This test method covers the determination of the heat
f
T = initial temperature of calorimeter, °C,
capacity of liquids and solids. It is applicable to liquids and c
T8 = T − T =temperature differential, °C,
f c
solids that are chemically compatible with stainless steel, that
R = resistance of nominal 1-V standard resistor,
haveavaporpressurelessthan13.3kPa(100torr),andthatdo
R = resistance of nominal 100-V standard resistor,
not undergo phase transformation throughout the range of test
R = resistance of nominal 10 000-V standard resis-
10 000
temperatures. The specific heat of materials with higher vapor
tor,
pressurescanbedeterminediftheirvaporpressuresareknown
E = emf across nominal 1-V standard resistor,
throughout the range of test temperatures.
E = emf across nominal 100-V standard resistor,
1.2 The values stated in SI units are to be regarded as
E = emf across nominal 10 000-V standard resis-
10 000
standard. The values given in parentheses are for information
tor,
only.
t = timeofapplicationofcalibrationheatercurrent,
c
1.3 This standard does not purport to address all of the
s,
safety concerns, if any, associated with its use. It is the
q = total heat developed by calibration heater, cal,
responsibility of the user of this standard to establish appro-
DE = total heat effect for container, mV,
c
priate safety and health practices and determine the applica-
DE = total heat effect for sample+container, mV,
s
bility of regulatory limitations prior to use. De = total heat effect for calibration of calorimeter
c
system during container run, mV,
2. Referenced Documents
De = total heat effect for calibration of calorimeter
s
2.1 ASTM Standards: system during sample run, mV,
DH = total enthalpy change for container changing
D1217 Test Method for Density and Relative Density (Spe-
c
from T to T ,
cific Gravity) of Liquids by Bingham Pycnometer
f c
DH = total enthalpy change for sample plus container
T
3. Terminology
changing from T to T ,
f c
DH = totalenthalpychangeforsamplechangingfrom
3.1 Definitions of Terms Specific to This Standard:
s
T to T ,
3.1.1 specific heat—the ratio of the amount of heat needed f c
F = calorimeter factor,
to raise the temperature of a mass of the substance by a
W = weight of sample corrected for air buoyancy
specified amount to that required to raise the temperature of an
d = density of sample at T,
f f
equal mass of water by the same amount, assuming no phase
d = density of sample at T ,
c c
change in either case.
V = total volume of sample container,
T
3.2 Symbols:
V = volume of sample vapor at T,
f f
V = volume of sample vapor at T ,
c c
P = vapor pressure of sample at T,
f f
This test method is under jurisdiction ofASTM Committee D02 on Petroleum
P = vapor pressure of sample at T ,
c c
ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.11on
N = moles sample vapor at T,
f f
Engineering Sciences of High Performance Fluids and Solids.
N = moles sample vapor at T ,
Current edition approved June 1, 2005. Published September 2005. Originally
c c
approved in 1968. Last previous edition approved in 2000 as D2766–95(2000).
N = moles sample vapor condensed,
DOI: 10.1520/D2766-95R05.
DH = heat of vaporization of sample,
v
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
R = gas constant, and
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
K = heat of vaporization correction.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.3 Units:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D2766 – 95 (2005)
3.3.1 The energy and thermal (heat) capacity units used in
this method are defined as follows:
1 cal (International Table)=4.1868 J
1 Btu (British thermal unit, International Table)=
1055.06 J
1 Btu/lb °F=1 cal/g °C
1 Btu/lb °F=4.1868 J/g K
3.3.2 For all but the most precise measurements made with
this method the rounded-off value of 4.19 J/cal can be used as
this is adequate for the precision of the test and avoids the
difficulty caused by the dual definition of the calorie.
4. Summary of Test Method
4.1 The enthalpy change, DH , that occurs when an empty
c
sample container is transferred from a hot zone of constant
temperature to an adiabatic calorimeter at a fixed initial
temperature is measured for selected hot zone temperatures
evenly spread over the temperature range of interest.
4.2 Theenthalpychange, DH ,thatoccurswhenacontainer
T
filled with the test specimen is transferred from a hot zone of
constant temperature, T , to an adiabatic calorimeter at a fixed
c
initial temperature is measured for selected hot-zone tempera-
tures evenly spread over the temperature range of interest.
4.3 The net enthalpy change per gram of sample is then
expressed as an analytical power function of the temperature
differential T8.The first derivative of this function with respect
to the actual temperature, T, yields the specific heat of the
f
sample as a function of temperature. Actual values of the
specific heat may be obtained from solutions of this equation
which is valid over the same range of temperatures over which
the total enthalpy changes, DH , were measured.
T
5. Significance and Use
5.1 The specific heat or heat capacity of a substance is a
thermodynamic property that is a measure of the amount of
energy required to produce a given temperature change within
a unit quantity of that substance. It is used in engineering
calculations that relate to the manner in which a given system
FIG. 1 Specific Heat Apparatus
may react to thermal stresses.
sensitivity, range, and a minimum of six digit resolution is
6. Apparatus
acceptable. A direct reading digital temperature indicating
6.1 Drop-Method-of-Mixtures Calorimeter, consisting es-
device may be substituted for the potential measuring device
sentially of a vertically mounted, thermostatically controlled,
for the purpose of measuring the temperature of the capsule
tube furnace and a water-filled adiabatic calorimeter. The
while in the tube furnace. See Fig. 3.
,
furnace is mounted with respect to the calorimeter in such a 34
6.4 Resistor,1-V precision type.
way that it may be swung from a remote position to a location 3,4
6.5 Resistor, 100-V precision type.
,
directlyoverthecalorimeterandreturnedrapidlytotheremote 34
6.6 Resistor, 10 000-V precision type.
position. The sample container may thus be dropped directly
6.7 Amplifier, zero centered range, linear response with
into the calorimeter with a minimum transfer of radiation from
preset ranges to include 625 µnV, 6100 µV, 6200 µV,
furnace to calorimeter. Details of construction are shown in
6500µV, 61000 µV, and 62000 µV; with error not to exceed
Fig. 1.
60.04%ofoutput;withzerodriftafterwarm-upnottoexceed
6.2 Sample Container—A stainless steel sample container
with a polytetrafluoroethylene seal suitable for use at tempera-
tures up to 533 K (500°F) is shown in Fig. 2.
If you are aware of alternative suppliers, please provide this information to
ASTM International Headquarters. Your comments will receive careful consider-
6.3 Potential Measuring Devices (two required), potential
ation at a meeting of the responsible technical committee, which you may attend.
measuring device capable of measurement of up to 1 V with a
The sole source of supply of the apparatus known to the committee at this time
−6
precision of 10 V or a potentiometer assembly with sensitiv-
isModels9330/1,9330/100,9330/10K,GuildlineInstruments,Inc.,103Commerce
ity of at least 1 µV or a digital multimeter with equivalent St., Ste 160, Lake Mary, FL 32795-2590.
D2766 – 95 (2005)
enthalpy change that must be deducted from DH to determine
T
DH;(2) simultaneously it affords a correction term that
S
cancels out the effect of conduction and radiation that occur
during sample transfer.
7.2 The following procedure is used to determine DH at
c
each selected temperature for each sample container over the
temperaturerangeofinterest(Note3):Bringtheemptysample
containertoaconstanttemperatureintheverticaltubefurnace.
Monitor its temperature with the copper-constantan thermo-
couple that is fitted into the center well of the container.While
the container is equilibrating, adjust the temperature of the
calorimeter by cooling or warming it as required to bring it to
atemperaturejustbelowtheselectedinitialstartingpoint(Note
4).Adjust the thermistor bridge so that it will have zero output
at the selected initial temperature. Any changes of this bridge
FIG. 2 Specific Heat Sample Cell
setting will require recalibration of the system. The amplified
output of the thermistor bridge is displayed on the recorder
60.5 µV offset within which drift will not exceed 60.2
(Note 5). As the calorimeter approaches the selected starting
µV/min. Equivalent instrumentation with different fixed poten-
temperature, the output of the bridge becomes less negative
tial ranges is acceptable provided the same overall potential
and approaches zero (the starting temperature). Just before the
ranges are covered.
output reaches zero, determine the temperature of the capsule
6.8 Strip Chart Recorder, with nominal 25 cm chart, 65
byreadingtheoutputofthecopper-constantanthermocoupleto
mV, zero center.
the nearest 1 µV (Note 6). At the moment the calorimeter
6.9 Binding Posts,lowthermalemf-type,withprovisionfor
temperature passes through the selected starting temperature,
guard circuit.
swing the vertical furnace over the calorimeter and drop the
6.10 Rotary Switch, low thermal emf-type, with provision
sample container into the calorimeter. Return the furnace
for guard circuit.
,
immediately to its rest position. As the calorimeter warms,
6.11 Thermistor Bridge.
3,5
adjustthepotentiometerbiastobringtherecordedtemperature
6.12 Thermistor.
traceonscale.Recordthetemperatureuntilitresumesanearly
6.13 Thermocouple, copper-constantan, stainless steel
3,6
sheath, 3.2 mm ( ⁄8 in.) in outside diameter. linear drift. Then determine the total heat effect, measured in
6.14 Power Supply, 24 V dc. millivolts, by taking the algebraic sum of the initial and final
potentiometer biases and the extrapolated differences in the
NOTE 1—Two 12 V automobile batteries in series have proved satis-
temperature traces (Note 7). In order to determine the exact
factory as a power supply. They should be new and fully charged.
energy equivalent of the millivolt change measured during the
3,7
6.15 Power Supply, constant-voltage, for potentiometer.
drop of the container, it is necessary to perform a heater run.
6.16 Standard Cell, unsaturated cadmium type, for potenti-
3,8 This run is made after every drop as the calibration of the
ometer.
system is a function of the size of the heat effect as well as of
7. Calibration
the water content of the calorimeter. Since the rate of energy
input from the electrical heater is of necessity much smaller
7.1 The enthalpy change, DH , that occurs when an empty
c
than that encountered in the drop itself, it is not possible to
sample container is transferred from the tube furnace at a fixed
duplicate the heat effect of the drop exactly. Instead, adjust the
temperatureintotheadiabaticcalorimeterisnotafunctiononly
of the composition of the container and the temperature temperature of the calorimeter so that the bias of the potenti-
difference between the furnace and the calorimeter. Because ometer is such that an electrical heat effect of known size will
heatlossesoccurastheresultsofbothconductionandradiation
occur over a range intermediate between the initial and final
from the container during the transfer process, some heat is
points of the drop (Note 8). During the heater run, measure the
also transferred by radiation to the calorimeter at the same
current through the heater and the potential drop across the
time. The measured value of DH as a function of temperature
c heaterbymonitoringthepotentialsacrossstandardresistors R
serves a dual purpose: (1) it provides the value of container
and R . Measure the time interval of application of heat to
10 0
the nearest 0.1 s, and determine the change in potential due to
the electrical heat effect by taking the algebraic sum of the
The sole source of supply of the apparatus known to the committee at this time
is VWR, Welch Div., Chicago, IL, under the following catalog number: Thermistor
initial and final potentiometer biases and the extrapolated
Bridge—No. S-81601; Thermistor—No. S-81620.
initial and final temperatures.
The sole source of supply of the apparatus known to the committee at this time
is Thermocouple Products Co., Inc., Villa Park, IL.
NOTE 2—If organic materials are to be studied, it is suggested that
The sole source of supply of the apparatus known to the committee at this time
fifteen determinations of DH made at roughly equal intervals over the
c
is No. 245G-NW-19, Instrulab, Inc., Dayton, OH.
temperature range from 311 to 533 K (100 to 500°F) will suffice in most
The sole source of supply of the apparatus known to the committee at this time
is Eppley Laboratory, Inc., Newport, RI. instances.
D2766 – 95 (2005)
FIG. 3 Specific Heat Measuring and Control Circuit Diagram
NOTE 3—Theinitialtemperatureisusuallyselectedtobeslightlylower error incurred if the procedure is followed is sufficiently small to be
thanaverageroomtemperaturesothatcalorimeterdriftduetostirringand insignificant even if fairly large (for example, up to 0.5 mV) deviations
deviations from complete adiabaticity will result in a slow, almost linear
from the midpoint are allowed.
drift through the selected starting temperature.
NOTE 4—Normally a 50 µV full-scale setting of the amplifier is used 7.3 Repeat the procedure described in 7.2 for each tempera-
and initial potentiometer bias is set at zero.
tureatwhichitisdesiredtocalibrateagivensamplecontainer.
NOTE 5—Provided that an accurate calibration of the thermocouple is
madepriortoitsuse,itshouldbepossibletodeterminethetemperatureto
8. Procedure
the nearest 0.1°C with accuracy.
NOTE 6—To compensate for differences
...
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