Twin Calorimeter Research Articles

Thermodynamic properties of phosphate members of the meta-autunite group: A high-temperature calorimetric study

Samples of synthetic analogs of uranyl phosphate minerals have been prepared at room temperature by slow mixing of reactants by a diffusion method. Reaction products were analyzed using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), inductively coupled plasma optical emission spectrophotometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS). Calorimetric measurements have been performed in a Calvet-type twin calorimeter using sodium molybdate (3Na2O-4MoO3) solvent at 976K as a flux. The enthalpy of formation from the binary oxides, ΔHf-ox, at 298K was calculated for each compound from the respective drop solution enthalpies, ΔHds. Calculated standard enthalpies of formation from the elements, ΔH0f, at 298K are −3425±9kJ/mol for meta-ankoleite (KUP), −6233±17kJ/mol for meta-autunite (CaUP), −6921±13kJ/mol for meta-torbernite (CuUP), −7254±17kJ/mol for meta-saléeite (MgUP), −3264±12kJ/mol for Rb-meta-autunite (RbUP), −3580±7kJ/mol for meta-natro-autunite (NaUP), −3692±11kJ/mol for Li-meta-autunite (LiUP), −6402±5kJ/mol for meta-uranocircite (BaUP), −3277±6kJ/mol for Cs-meta-autunite (CsUP), and −7109±19kJ/mol for Co-meta-autunite (CoUP). The results exhibit trends of the thermodynamic stability of these compounds. The normalized charge deficiency per anion (NCDA) approach relates the thermodynamic stability of these compounds to their crystal structures. The thermodynamic stability of uranyl phosphate minerals is important for understanding their formation in Nature, as well as their fate in a geological repository for nuclear waste, and their existence in the subsurface of anthropogenically contaminated environments.

A well-plate format isothermal multi-channel microcalorimeter for monitoring the activity of living cells and tissues

Design and properties are reported for a novel type of multi-channel isothermal microcalorimeter. It is equipped with 48 calorimetric units (channels) and is primarily intended for use as a monitor of the activity of living cells, tissues and small animals. Calorimetric vessels are positioned in a holder with the format of a 48-well microtiter plate. At most, 47 samples can be measured simultaneously; one vessel is then used as reference. The standard configuration is 32 sample positions using 16 channels as references in a twin calorimeter setup. The detection limit is then 0.1μW. Sample volumes are usually 100μl–300μl. The 24h baseline stability is typically 0.2μW (room temperature variation ≤1°C). The instrument was designed considering feasible uses in applied biology, especially in pharmaceutical and clinical laboratories and in environmental work. However, it can be employed as a general monitor of slow processes in different fields of biology and for non-biological systems, including accurate determination of their thermal powers (heat production rates). In the present report, properties of the instrument are characterized by chemical calibration experiments and in measurements of growth of bacteria and mammalian cells.

The influence of carbon dioxide-induced water acidification on the osmotic and metabolic responses of the Baltic amphipod Gammarus oceanicus

The aim of this study was to investigate the effect of CO2-induced water acidification (pH values: 8.1 − control, 7.5 and 7.0) on the hemolymph osmolality and total metabolic rate of amphipod Gammarus oceanicus under short-term exposure. The hemolymph osmolality was measured using a vapor pressure osmometer. The metabolic rate was determined based on the heat dissipation measurements using a Calvet-type isothermal twin calorimeter. The hemolymph osmolality remained unchanged after exposure to pH 7.5 and it increased in the lowest treatment. Acidification did not significantly affect the resting or active metabolic rate. The observed results indicate that high osmolality maintained during hypercapnia did not generate additional physiological costs. It may therefore be concluded that the studied species is preadapted for this factor. The long-term adaptation to hypoosmotic conditions in the brackish Baltic Sea might also have preadapted it to hypercapnia because similar physiological mechanisms are responsible for the resistance to both factors.

The Effect of CO2-Induced Seawater Acidification on the Behaviour and Metabolic Rate of the Baltic ClamMacoma balthica

The aim of this study was to investigate the effect of CO2-induced seawater acidification (pH 8.1; control pH 7.0 and 6.0) on the survival, behaviour and metabolic rate of the Baltic clam Macoma balthica during short- (36 hours) and long-term (14 days) exposures. Total metabolic rate and gaping behaviour (shell opening and closing) were determined based on heat dissipation measurements using an isothermal twin calorimeter of the Calvet type. The survival and burrowing behaviour during long-term exposure were observed every day. Short-term exposure to reduced pH did not significantly affect the resting or active metabolic rate. Neither were there any significant changes in gaping behaviour. However, long-term exposure significantly affected burrowing behaviour. In the lowest-pH treatment, both resting and active metabolic rates were also significantly higher than in the control.

Metabolic rate and activity of blue mussel Mytilus edulis trossulus under short-term exposure to carbon dioxide-induced water acidification and oxygen deficiency

This work investigated the effect of carbon dioxide-induced decreased water pH (8.1 – control, 7.5 and 7.0), oxygen saturation (~100% and ~20%) and the combination of both factors on the behaviour (gaping activity) and the total metabolic rate of blue mussel Mytilus edulis trossulus from the southern Baltic Sea. Heat dissipation measurements were carried out in a Calvet-type isothermal twin calorimeter equipped with a flow-through system. The resting metabolic rate was not significantly (p > 0.05) affected by pH or oxygen saturation. Neither was there significant (p > 0.05) effect of the interaction of both factors on this process. The high inter-individual variability in behaviour affected the value of maximal recorded activity and duration of activity peaks connected with shell gaping behaviour. In some mussels, they were short and appeared periodically, and other individuals were inactive or exhibited temporal activity terms of different duration. The lowered oxygen saturation significantly (p < 0.05) affected the time spent on activity. However, there was no effect (p > 0.05) of lowered pH on this parameter, which indicates that oxygen deficiency may affect the Baltic population of M. edulis trossulus more seriously than acidification.

Monitoring the heat production of small terrestrial animals by a twin calorimeter

Calorimetric investigations of terrestric animals of smaller size were performed in (1) Calvet‐type isoperibol twin instruments of up to 100 mL in content, (2) a “poor man's calorimeter” of up to 24 L in volume, in single and twin setups for colonies of honeybees, stingless bees, bumblebees, and hornets, and (3) a roundabout flight calorimeter for smaller insects. Special questions of metabolism concerning sleep and heat output rates of different castes in honeybees or of increasing numbers of individuals in a group were of interest. The most simple animals in these investigations were soil‐living species like earthworms, woodlice, pill bugs, and carabid beetles; they were investigated for their routine heat production rates and the rates under the influence of the effective uncoupler of oxidative phosphorylation, pentachlorophenol. The highest animals were lacertide lizards and snails, which were monitored for their standard metabolism and for stimulated reactions, to gather information about their scope of metabolism.

Kinetics and enthalpy of crystallization of uric acid dihydrate

The kinetics of crystallization of uric acid dihydrate in aqueous solution with a constant ionic strength 0.3moldm−3 NaCl and at thermodynamic and physiological temperature (25 and 37°C) was studied using isoperibolic reaction twin calorimeter. The enthalpy of crystallization ΔcrH=−47.3±0.9 and −46.2±1.4kJmol−1and kinetic constant kg=2.0×10−8 and 9.6×10−8m4s−1mol−1 were determined at 25 and 37°C, respectively.

Anomalous heat capacity of high‐density polyethylene melts at high temperature

AbstractThe first measurements of heat capacity of high‐density polyethylene have been obtained for melts in the high‐temperature region of 180–260°C. A heat‐flow twin calorimeter was used. Abrupt transitions are noticed at 212 and 228°C, analogous to transitions seen earlier with rheological and surface tension measurements. Possible explanations for these phenomena are offered. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A calorimetric study of the temperature effect on Calcium Phosphate precipitation

The precipitation of calcium phosphate was studied using a heat flow twin calorimeter (C80, Setaram, France). The process was carried out using two identical membrane vessels. In the lower parts of both vessels 2 mL of a supersaturated solution (solution A) containing Ca(H2PO4)·2H2O (0.054 M) and CaCl2·H2O (0.125 M) with a molar ratio Ca/P = 1.67 were added. Then 0.05 mL of an ammonium solution (25% w/w) (solution B) and 0.05 mL of distilled water were transferred in the upper parts of sample and reference vessels, respectively. After temperature had been maintained at 303, 313, 323 and 333 K the membranes of both sample and reference vessels were broken simultaneously. The precipitation process also repeated with the same conditions for periods of 15, 60 and 120 min in a bath. The first two calorimetric curves (303, 313 K) show a single exothermic step during the process as a sharp peak in the initial stage. On the contrary at the experimental temperature of 323 K except of the sharp peak in the initial stage, a steadily exothermic tendency appears after 100 min time. In higher temperature (333 K) the sharp peak appears in the initial stage followed by a broad exothermic step between 75 and 320 min time. The XRD analyses show that the solids in the initial experimental stages are mainly consisted of dicalcium phosphate dihydrate (DCPD) for the lower temperature and a biphasic or triphasic system consisted of hydroxyapatite (HA), dicalcium phosphate anhydrous (DCPA) and octacalcium phosphate (OCP) for the rest temperatures. The XRD analyses show also that during the solution aging the initial products are transformed into the more stable thermal forms of HA and octacalcium phosphate (OCP).

Calorimetric study of dissolution kinetics of phosphorite in diluted acetic acid

In this report, we present a thermodynamic and kinetic study of the selective dissolution of calcite from low-grade phosphate ores (Epirus area, Greece) by dilute acetic acid at isothermal conditions. A twin calorimeter with two identical membrane vessels, for the acid dissolution process, and for the reference was used. The curves of rate vs. time of the phosphorite dissolution for various temperatures show that the maximum (.qmax) was increased, whereas the time (tpeak) to achieve the corresponding .qmax values was decreased, as the experimental temperature was increased. The dissolution enthalpy was increased from 13.1 to 16.7 kJ mol−1, as the experimental temperature was increased from 10.0 to 28.0°C. The chemical analysis of the supernatant solutions shows that the main process was the calcite dissolution. The reaction model with general form, ln(1/(1-X))=ktm, was found to fitted the experimental data regardless of the experimental temperature. These results were assigned in the presence of two different kinds of particles in the phosphorite. The activation energy of the dissolution process was found 69.7 kJ mol−1. The SEM micrographs of acid dissolution samples showed two different textures after acid dissolution.

Surface Energetics of Nanocrystalline YSZ Powders

AbstractNanocrystalline 8 and 12 mol % yttria stabilized zirconia (YSZ) powders with fluorite-type structure were synthesized by a precipitation method. Powders were characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetry, and nitrogen adsorption analyses. Precipitation produced amorphous powder which crystallized at approximately 450-470 °C into a cubic phase with a crystallization enthalpy ranging from 13.7 ± 0.6 kJ/mol for 8YSZ to 11.7 ± 0.5 kJ/mol for 12YSZ. Integral heat of water adsorption at room temperature measured on 8YSZ was -63 ± 2 kJ/mol for coverage 4.1 ± 0.1H2O/nm2. Drop solution calorimetry experiments were performed in a custom made Calvet twin calorimeter using sodium molybdate 3Na2O 4MoO3 solvent. The preliminary values for surface enthalpies of hydrated surfaces are 0.8 ± 0.1 J/m2 for 8YSZ and 1.3 ± 0.1 J/m2 for 12YSZ.

Thermochemical characterization of Ca4La6(SiO4)6(OH)2 a synthetic La- and OH-analogous of britholite: implication for monazite and LREE apatites stability

Thermochemical characterization of Ca4La6(SiO4)6(OH)2a synthetic La- and OH-analogous of britholite: implication for monazite and LREE apatites stabilityIn this contribution, monazite (LREEPO4) solubility is addressed in a chemical system involving REE-bearing hydroxylapatite, (Ca, LREE)10(PO4,SiO4)6(OH)2. For this purpose, a synthetic (La)- and (OH)-analogous of britholite, Ca4La6(SiO4)6(OH)2, was synthesised and its thermodynamic properties were measured. Formation enthalpy of -14,618.4±31.0 kJ·mol-1was obtained by high-temperature drop-solution calorimetry using a Tian-calvet twin calorimeter (Bochum, Germany) at 975 K using lead borate as solvent. Heat capacities (Cp) were measured in the 143-323 K and 341-623 K ranges with an automated Perkin-Elmer DSC 7. For calculations of solubility diagrams at 298 K, the GEMS program was used because it takes into account solid solutions. In conditions representative of those expected in nuclear waste disposal, calculations show that La-monazite is stable from pH = 4 to 9 with a minimum of solubility at pH = 7. La-bearing hydroxylapatite precipitates at pH &gt; 7 with a nearly constant composition of 99% hydroxylapatite and 1% La-britholite. Each mineral buffers solution at extremely low lanthanum concentrations (log{La} = 10-10-10-15mol·kg-1for pH = 4 to 13). In terms of chemical durability, both La-monazite and La-rich apatite present low solubility, a requisite property for nuclear-waste forms.

Thermal investigations of a nest of the stingless bee Tetragonisca angustula Illiger in Colombia

Thermal investigations were performed in Colombia on a colony of the stingless bee Tetragonisca angustula by means of thermometry and direct calorimetry. To this end, a nest with approximate 5000 individuals was collected in the field and transferred to a twin calorimeter, where the bees continued their normal life and development. Two camping boxes (Poor Man's Calorimeter, PMC) with Peltier elements as cooling systems were used as a differential system. Each box had a volume of 8 L and a sensitivity of 19.2 mV W −1. The PMCs were modified to give forager bees a free access to the environment. The thermal situation within the colony was monitored calorimetrically and thermometrically. 10 kΩ of NTC resistors were distributed at special points of the brood combs, storage pots and involucrum. The thermometric and calorimetrical signals were recorded continuously over 3 months by a four-channel data logger.

Construction and test of a tungsten/Sci-Fi imaging calorimeter for the CREAM experiment

Cosmic Ray Energetics And Mass (CREAM) is a balloon-borne experiment designed to perform direct measurements of cosmic ray composition over the elemental range from proton to iron to the supernova energy scale of 10 15 eV in a series of balloon flights using the new Ultra Long Duration Balloon (ULDB) capability under development by NASA. The first flight of CREAM will take place at the end of 2004 from Antarctica. The instrument includes a sampling tungsten/scintillating fiber calorimeter preceded by a graphite target with scintillating fiber hodoscopes, a pixelated silicon charge detector, a transition radiation detector and a segmented timing-based particle-charge detector. The thin ionization calorimeter has been designed to operate in the range of energies from a few hundred GeV to 1 PeV providing imaging capability in the reconstruction of the showers originating from the interaction of primary nuclei in the carbon target. A twin calorimeter for the second CREAM payload has been built and tested at CERN. Its construction technique and preliminary test results are presented.

An analytical expression of the output of a power-compensated DSC in a wide temperature range

We present an upgrade of our previous theoretical model of a power-compensated twin calorimeter with particular reference to the DSC-7 manufactured by Perkin-Elmer. The aim of this generalization is to provide an analytical description of a measured heating curve in a fairly wide range of temperature. To reach this goal, we emulate the “ΔT balance” (ΔTB) control and the “slope” (SL) control of the DSC-7, which are used to modify curvature and slope of a measured curve. The implementation of these two functions has simply required the introduction of three new parameters. In this way, we got a fairly good analytical description of the calorimeter response, when the holders are empty, whatever the setting of both controls. We present results in the temperature range from 248 to 423K. One of the above mentioned parameters turns out to be linearly dependent exclusively on the ΔTB; while the other two are linearly dependent both on the ΔTB and SL. These results provide the means to get a calibration of the instrument with respect to the ΔTB and SL settings.

The effect of gas pressure on the melting behavior of compounds

The melting and crystallization behavior of pure compounds under gas pressure was experimentally investigated using a scanning transitiometer, which is a sensitive twin calorimeter combined with a computer driven PVT control. This technique allows to determine different thermodynamic effects occurring with changes of state. While one of the three state variables pressure P, volume V, or temperature T is kept constant, another one is changed with time, both the enthalpy effect and the change of the remaining third state variable can simultaneously be measured with high precision. Thermodynamic equilibrium can be achieved during the entire process because the state is changed very slowly. The solid–liquid phase change of dimethylterephthalate (DMT) and biphenyl was investigated under He, CO 2, and N 2O pressure up to 30 MPa, and the SLG three phase lines were determined. The solid–liquid phase change appeared unexpectedly as a pair of two different heat signals.

A new general-purpose isothermal microcalorimeter for use at temperatures up to 200 °C

The design and some properties of a new general-purpose isothermal microcalorimeter are reported. The instrument is a twin thermopile heat conduction calorimeter, which is designed for use up to 200 °C. The calorimetric units and surrounding heat sink are suspended inside a hollow aluminium construction, which is thermostated. Above that unit a second thermostated block is positioned and the whole assembly is suspended inside a Dewar vessel. When the instrument is used at room temperature and below, the thermostated units are cooled by use of an insertion Peltier effect cooler. The instrument can be used with a wide range of different reaction vessels (diameter 14 mm). Baseline experiments have been conducted in the temperature range 15–200 °C. Typical values obtained during 10 h periods at 200 °C are ±3 and ±10 nW for the baseline drift and baseline fluctuations, respectively. The heat detection limit, determined by release of electrical energy, is about 2 μJ. Preliminary stability measurements have been conducted at 100 °C on samples of stabilised and non-stabilised polyamide film.

Developments in coaxial power standards at NPL

A 2.4 mm twin line coaxial calorimeter is the first microwave power standard in this line size to be developed at the National Physical Laboratory (NPL). The design is based on a twin line coaxial calorimeter where RF power dissipated in one load is measured in terms of a DC power dissipated in a similar load with its effective efficiency derived from a thermal and electrical analysis of the twin lines. The calorimeter will provide traceable power measurements from DC to 50 GHz between power levels of 0.1 and 10 mW with an uncertainty ranging from 0.5% at 10 MHz to 2.3% at 50 GHz at the 1 standard deviation level.

Calorimetric Characterization of Different Yeast Strains in Doughs

In this work microbial growth and metabolism of Saccharomyces cerevisiae from three different strains in a bread dough system were investigated by means of SETARAM C80D twin calorimeter in isothermal conditions at various temperatures. The overall calorimetric signal accounts for two main contributions, namely oxidative and anaerobic degradation of substrate.

Calcium oxalate crystallization kinetics from calorimetric measurements

The kinetics of calcium oxalate monohydrate precipitation effected by mixing aqueous solutions of calcium chloride and sodium oxalate together in the stoichiometric ratio at 25 and 37°C, were studied using an isoperibolic reaction twin calorimeter. A method for inferring the crystal growth kinetic parameters from experimental progress curve giving the time development of the integral heat evolved during the precipitation is suggested and verified. Results obtained for calcium oxalate monohydrate compare favourably with those obtained with conventional techniques for studying crystallization.