Calorimetry Conference Research Articles

An adiabatic calorimeter for samples of mass less than 0.1 g and heat-capacity measurements on benzoic acid at temperatures from 19 K to 312 K

An adiabatic calorimeter was constructed for samples of low mass. By placing its thermometer on the adiabatic shield surrounded the calorimetric cell, the internal volume of the cell could be reduced to 0.1 cm 3. The molar heat capacities C p, m of a sample of mass 69.85 mg of standard benzoic acid were measured from T = 18.94 K to 311.58 K. The deviations from the values of C p, m recommended by the U.S. Calorimetry Conference were ±0.1· C p, m at T < 40 K, -(0.02±0.02)· C p, m from T = 40 K to 110 K, and better than ±0.015· C p, m at T > 110 K, and their causes were discussed. The molar enthalpy increment Δ 298.15 K 0 H o m, and molar entropy increment Δ 298.15 K 0 S om of benzoic acid were 2.868·10 3· Rmiddot;K and 19.93· R, respectively, where R is the gas constant (8.31451 J·K -1·mol -1), which were smaller by 0.8 per cent and 1.2 per cent than the values calculated from the recommended molar heat capacities.

Frozen-in disorder and slow relaxation in crystals. (Being the 40th Huffman Memorial Award Lecture of the Calorimetry Conference delivered on 20 August 1992 at its 47th annual Conference organized jointly with IUPAC Conference on Chemical Thermodynamics held at Snowbird, UT, U.S.A.)

Frozen-in disorder and slow relaxation in crystals. (Being the 40th Huffman Memorial Award Lecture of the Calorimetry Conference delivered on 20 August 1992 at its 47th annual Conference organized jointly with IUPAC Conference on Chemical Thermodynamics held at Snowbird, UT, U.S.A.)

A statistical-thermodynamic view of cooperative structural changes in phospholipid bilayer membranes: their potential role in biological function

It is a great honor to receive the Huffman Memorial Award from the Calorimetry Conference. Such an honor was certainly not on my list of expectations when I first became interested in calorimetric experimentation over 20 years ago. I thank the conference for this honor and the many of you who have aided and encouraged the work which this award recognizes. In 1969, I had the opportunity to spend three months in the laboratories of the late Stig Sunner and Ingemar Wadsii at the University of Lund, Sweden. It was during that visit that I first became acquainted with state-of-the-art calorimetric equipment. That visit provided me the opportunity to explore from a practical perspective the many possibilities of applying calorimetric techniques to probe the thermodynamic details of questions of biological interest. My interest in, and motivation for, using calorimetric techniques has always been driven by specific thermodynamic questions related to biological systems. The original questions were related to understanding the thermodynamic mechanism of unfolding of globular proteins in aqueous solution. In the early sixties these thermally induced unfolding transitions were assessed by spectroscopic changes primarily and calculation of thermodynamic quantities associated with the process required that the two-state approximation (i.e. the protein existed in one of only two thermodynamic states) be valid, an assumption which had no previous means of being proven. Additionally, in 1964 Brandts(‘**) put forth a phenomenological

Quantitative analysis of linkage in macromolecules when one ligand is present in limited total quantity.

We present a general framework for analysis of two closely related problems in biochemical studies: (1) The first is analysis of binding data obtained under conditions in which a second, linked ligand is present in limited total quantity. In such conditions the free activity of the second ligand varies throughout the primary ligand binding curve, and the resultant behavior can be quite complex. Analysis of such curves enables one to quantitatively extract detailed information regarding the linkage of the two ligands at intermediate stages of ligation. The treatment is applied in an accompanying paper to oxygen binding in human hemoglobin in the presence of organic phosphates [Robert, C.H., Fall, L., & Gill, S. J. (1988) Biochemistry (following paper in this issue)]. (2) The second treatment we outline regards the analogous problem of analyzing differential scanning calorimetry (DSC) data obtained for a macromolecule binding a ligand present in limited quantity. A simple model is presented that accounts for dual transitions like those already seen in DSC data for human serum albumin in the presence of nonsaturating amounts of fatty acids [Ross, P., & Shrake, A. (1987) Abstracts of the 42nd Calorimetry Conference, University of Colorado, Boulder, CO].

A very low-temperature calorimeter with a ( 3He+ 4He) dilution refrigerator The heat capacity of trans-bis(ethylenediamine)-bis(isothiocyanato)nickel(II)

A calorimeter with a ( 3He+ 4He) dilution refrigerator capable of measuring heat capacity between 20 mK and 25 K has been constructed. The calorimeter works under three operational modes in accordance with the temperature region suitable for heat-capacity measurements: the isoperibol low-temperature mode covers the range below 200 mK, the adiabatic high-temperature mode is used in the range from 0.2 to 25 K, and the isoperibol third mode is adopted when the thermal relaxation time of a sample is long. The accuracy of the calorimeter has been determined indirectly by comparing heat capacities of a common sample with those measured by a 3He calorimeter whose accuracy has been established on the basis of the 1965 Calorimetry Conference Copper Standard. The heat capacity of a paramagnetic nickel complex [Ni(en) 2(NCS) 2] (en = H 2NCH 2CH 2NH 2) has been measured between 0.3 and 20 K. A Schottky anomaly centred around 3.3 K was detected. This anomaly was well accounted for in terms of the zero-field splitting of a single nickel ion arising from the crystalline-field anisotropy. The best fit between theory and experiment was obtained for D k = 8.98 K and |E| k = 1.62 K (or |E| D = 0.18 ) where D and E are the uni- and bi-axial crystalline-field anisotropy parameters, respectively, and k is the Boltzmann constant. The heat-capacity anomaly can likewise be accounted for in terms of different set of the parameters ( D k = −6.92 K and |E| k = 3.67 K or | E D | = 0.53 ) because both the sets bring about identical splitting with respect to the spin energy-level.

An adiabatic low-temperature calorimeter for small samples

A low-temperature adiabatic microcalorimeter for heat capacity determination was developed. The calorimeter is of the twin type, consisting of a sample cell and thermometric copper block. The temperature of the cell is transferred to the block by a fine thermocouple and a controlling system, and the temperature of the block is measured by standard thermometry. This reduces heat transfer through thermometer leads and thus avoids self-heating due to thermometric current. Heat capacities of two sample cells, one is 0.6 cm3 and the other 1.2 cm3 in the internal volumes, were measured in the temperature range between 13 and 300K with discontinuous heating mode. Accuracy of the calorimeter was tested by a US calorimetry conference standard benzoic acid crystal. The estimated inaccuracy is 1% at 20K, 0.1% at 70K and 0.3% above 170K.

A Simple Microcomputer-controlled Calorimeter: the Heat Capacity of Copper, Invar and RbNiCl3 in the Range 2?20 K

A simple inexpensive microcomputer has been used to control an adiabatic pulse-type calorimeter. The data acquisition control system incorporates a Rockwell AIM65 microcomputer to control all aspects of the thermometry and the injection of the heat pulse into the sample. Details of the hardware and software requirements are discussed, including the interface of the system with a host computer that uses the UNIX operating system. The performance of the apparatus was evaluated by measuring the heat capacity of 1965 Calorimetry Conference copper between 2 and 20 K. The results show a total r.m.s. deviation of less than 0�4 % and agree well with the copper reference equation (r.m.s. deviation 0�4 %). Measurements are also presented of the heat capacity of Invar (Nilo 36) and RbNiCI3 over the same temperature range. In the case of RbNiCh the heat capacity anomaly associated with the paramagnetic-anti ferromagnetic transition is observed at 11�1 K.

An adiabatic calorimeter for use at superambient temperatures. The heat capacity of synthetic sapphire (α-Al 2O 3) from 300 to 550 K

We report the construction of a superambient temperature adiabatic heat-capacity calorimeter which has been successfully operated from 300 to 550 K. We detail results on the heat capacity of a portion of the Calorimetry Conference sample for α-Al 2O 3. These results are compared with those of other investigators.

Construction of a 3He Calorimeter and Heat Capacity Measurement of the 1965 Calorimetry Conference Copper Standard between 0.4 and 20 K

Abstract Construction of an isoperibol-type calorimeter with a 3He cryostat is described. A system of charcoal-adsorption-pump is adopted. A Ge-thermometer used in the heat capacity measurements is calibrated in the temperature range from 0.4 to 1.5 K against the magnetic susceptibility of chromium potassium alum. The precision and the accuracy of the calorimeter is ascertained by the heat capacity measurement of the 1965 Calorimetry Conference Copper Standard (T-8.6) in the temperature range from 0.420 to 19.46 K. The deviation of the experimental points from the “copper reference equation” is within the experimental error of ±2.5% between 0.4 and 0.9 K, ±1.5% between 0.9 and 1.5 K, ±1.2% between 1.5 and 4 K, and ±0.6% between 4 and 20 K. The highest deviation of absolute value of the present heat capacity data of copper is 1.86% smaller than the “selected values (Furukawa et al.)” around 6 K. This difference may be primarily attributable to the NBS-65 temperature scale adopted in the present experiment.

8th Japanese calorimetry conference

8th Japanese calorimetry conference

Calorimetric determination of the heat of reaction of solid tris(hydroxymethyl)aminomethane with 0.1 M HCl solutions at 10, 25 and 40°c

The heat of reaction of solid tris(hydroxymethyl)aminomethane (THAM) with 0.1 M hydrochloric acid solution has been determined calorimetrically at 10, 25, and 40°C. The experimental conditions suggested by the Standards Committee of the U.S. Calorimetry Conference were followed. Values of Δ H° of −7.644±0.014, −7.104± 0.008, and −6.555±0.012 kcal/mole at 10, 25, and 40°C, respectively, are reported. Results of the study are compared with those of other workers, and THAM is recommended for use as an interlaboratory comparison standard for solution calorimetry.

A guide to procedures for the publication of thermodynamic data

At the 1971 Washington, D.C. meeting of the IUPAC Commission on Thermodynamics and Thermochemistry it was resolved that the following guide should be given the widest publicity to aid in the resolution of some current problems in scientific communication and in the hope that it might stimulate similar action by other organizations concerned with specialized fields of science. This guide was previously ratified by the All-Union Calorimetry Conference (U.S.S.R), The Calorimetry Conference (U.S.A.), the Experimental Thermodynamics Conference (U.K.), the Society of Calorimetry and Thermal Analysis (Japan), and the Société Français des Termiciens (France).

Measurement of the Relative Enthalpy of Pure α-AI2O3 (NBS Heat Capacity and Enthalpy Standard Reference Material No. 720) from 273 to 1173 K.

The relative enthalpy of NBS Standard Reference Material No. 720 (99.98 percent pure, single-crystal α-Al2O3, a calorimetrie heat-capacity standard) was measured over the range 273 to 1173 K by the drop method using a highly precise Bunsen ice calorimeter. Enthalpy data over the same temperature interval were obtained also on the Calorimetry Conference Sample of this substance. These results are believed to be more accurate than similar NBS results on the latter sample published in 1956, and show no significant discontinuity with the NBS data on the same substance that covered the ranges 13 to 380 K and 1173 to 2257 K. The average deviation from the mean for all enthalpy measurements on the SKM 720 sample was 0.017 percent, and the smooth enthalpy values derived from the data were estimated to be accurate to 0.1 percent. The precautions observed in order to minimize measuring errors are described in detail. The data are compared with many sets of the most reliable published data available and new recommended values for the thermodynamic functions of α-Al2O3 are presented for the interval 0 to 1200 K.

A calorimeter for the range 1 to 30 K the heat capacity of copper and glycerol glass

A calorimeter has been built for the measurement of heat capacities between about 1.3 and 30 K. Two germanium thermometers have been calibrated using the vapour pressures of e-H 2, 4He, and 3He, and a constant volume gas thermometer. The gas thermometer was standardized against the e-H 2 vapour pressures in the range 15 to 20 K with temperatures calculated from the vapour pressures on the International Practical Temperature Scale of 1968. Temperatures derived from the gas thermometry measurements are about 8 mK higher near 4 K than those derived from the 4He vapour pressures on the basis of the 1958 4He temperature scale, in agreement with other recent work. The heat capacity of a 1965 Calorimetry Conference Copper Standard specimen was measured between 1.4 and 20 K. The precision of the results is high: the mean deviation of experimental points from a smooth curve is 0.17 per cent. Comparison with other work shows that the absolute accuracy of the results is everywhere certainly better than 1 per cent and probably about 0.5 per cent. Glassy glycerol has been used as a thermal contact medium and its heat capacity has been measured between about 1.9 and 25 K, with results in satisfactory agreement with previous work.

Low Temperature Specific Heat of Copper: Comparison of Two Samples of High Purity

We have compared with good precision between 1.5 and 20 K the specific heat of two well characterized copper samples with residual resistivity ratio R(293 K)/R(4 K) of approximately 2000 (Calorimetry Conference, Argonne National Laboratories) and 30 000 (National Bureau of Standards, Boulder), and find that the electronic specific heat of the former is about 1% higher in the range 1.5–5 K, although the Debye temperatures are the same. The total specific heat of the former is up to 0.8% higher throughout the 1.5–20 K range. This discrepancy indicates that the specific heat may depend on the residual resistivity ratio. The germanium thermometer used in the measurements was calibrated against the National Bureau of Standards acoustic temperature scale T65, and so a test has been made of the smoothness of that scale.

Anharmonic effects in the thermodynamic properties of solids I. An adiabatic calorimeter for the temperature range 25-500 $deg$C: the heat capacities of Al2O3, Al and Pb

The importance of accurate high-temperature thermodynamic data for the study of anharmonic effects in solids is discussed, and an adiabatic calorimeter for the measurement of heat capacities in the temperature range 25-500 °C is described. The precision of the heat capacity data is about ±01% for T 400 °C. Measurement of the heat capacity of a Calorimetry Conference sample of Al2O3 shows that the accuracy of the calorimetry is probably better than ±02% throughout the whole temperature range studied. Results have been obtained for lead to near the melting point and for aluminium to 500 °C. For lead a contribution to Cp is observed for T > 250 °C which is attributed to vacancy formation; a value of 052 ±026 ev is derived for the enthalpy of formation of a vacancy.

Calibration and Use of Germanium Resistance Thermometers for Precise Heat Capacity Measurements from 1 to 25°K. High Purity Copper for Interlaboratory Heat Capacity Comparisons

The cryogenic apparatus and techniques used to calibrate 3 platinum-encapsulated 4-lead germanium resistance thermometers for use in precision calorimetry from 1 to 25°K are described. The calibration data for each thermometer were fitted with the aid of a digital computer by a polynomial expressing logR in terms of powers of logT. The sensitivity and temperature-cycling stability of these thermometers were adequate to recommend this type of temperature sensor for accurate low temperature calorimetry. A test of the temperature scale and of an isothermal type calorimeter was made by measuring the heat capacity of a sample of 99.99+% copper from the 1965 Calorimetry Conference Copper Standard and comparing the results with those obtained by other investigators. An equation to represent the heat capacity of pure copper from 1 to 25°K, based upon appropriate literature results and the present data, is offered as a convenient copper reference equation for intercomparison of heat capacity results from various laboratories.

High-temperature adiabatic drop calorimeter, and the enthalpy of ?-alumina

An adiabatic vacuum calorimeter of the copper-block type, for measuring enthalpies in the region 350–1800°K, is described. The quantities of heat measured by means of a platinum resistance thermometer located on the central axis of the calorimeter, and a thermometer of the Maier type wound on its outer surface, are identical within the limits of experimental error. The enthalpy of the Calorimetry Conference sample of α-alumina has been determined in the temperature range 400–1250°K, using adiabatic and non-adiabatic techniques. Both sets of data are in excellent agreement with the values computed from the National Bureau of Standards “corrected” equation, the mean deviations being ± 0.07 % and ± 0.09 % respectively.

Isothermal Drop Calorimeter for Alpha Active, Pyrophoric Materials

A copper block drop calorimeter to measure the heat content of intensely alpha active materials has been constructed. The furnace, calorimeter, and aluminum isothermal jacket are contained within an inert atmosphere glovebox. This permits the use of unencapsulated materials without exposing personnel to an alpha contamination hazard. The inert atmosphere also permits measurements to be made on materials which are pyrophoric in air. The apparatus is equipped with a suppressed range recorder to monitor continuously the resistance thermometer signal with a resolution of ±0.4 cal/μV. Electrical calibration of the calorimeter yielded a precision of ±0.08% in the thermometer and recording system. The heat content of a sample of Calorimetry Conference sapphire obtained from the National Bureau of Standards was measured, and the results deviated from the Bureau's reported data a maximum of 1.0% at 1008°K. The useful range of the apparatus extends from 306 to about 1450°K.

CONTINUOUS-HEATING ADIABATIC CALORIMETER FOR THE RANGE 300 TO 475 °K—THE SPECIFIC HEAT OF α-Al2O3

A continuous-heating calorimetric apparatus with semiautomatically controlled adiabatic shields is described. The calorimeter vessel is of novel construction. Measurements on the Calorimetry Conference Standard Sample of Aluminum Oxide give results about 0.25% higher than those tabulated by Furukawa et al. (1956).