Showing papers on "Calorimeter published in 1969"
TL;DR: An isothermal displacement calorimeter has been constructed and used to measure the enthalpies of mixing for the systems benzene+cyclohexane at 25 °C and benzene + carbon tetrachloride at 25°C as mentioned in this paper.
175 citations
TL;DR: A flow calorimeter for measurements of enthalpies of mixing is described in this paper, which has been used to make a series of measurements on n -hexane + cyclohexane at 298.15 K with a view to recommending that pair of liquids for checking new calorimeters.
84 citations
TL;DR: In this article, anisothermal dilution calorimeter of the Van Ness type is described, suitable for studying either endothermic or exothermic mixing, and the results of measurements of enthalpies of mixing are presented.
68 citations
TL;DR: In this paper, a new calorimeter has been developed and the enthalpy of solution of methanol, ethanol, propan-1-ol, propane-2-ol and butan- 1-ol was measured between 5° and 35°.
Abstract: A new calorimeter has been developed and the enthalpy of solution of methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, and 2- methylpropan-2-ol, in water to low concentrations, measured between 5° and 35°. In all cases, the results can be adequately represented by a quadratic dependence of heat of solution on temperature. The results have been compared qualitatively with the data for the hydrocarbons.
65 citations
TL;DR: In this paper, a fast differential calorimeter is described which permits the observation of heating caused by the relaxation of the lowest triplet states of organic molecules formed by flash excitation.
Abstract: A fast, sensitive differential calorimeter is described which permits the observation of heating caused by the relaxation of the lowest triplet states of organic molecules formed by flash excitation. From the ratio of slow to total heating after flash excitation, we calculate Φt, the quantum yield of triplet formation. The detection of the small amounts of heat involved (∼10−5 cal) is accomplished by means of a capacitor microphone transducer which measures volume changes caused by the heating. The response time (∼100 μsec) is determined by the lowest cavity resonance of the sample cell. At room temperature we find for anthrance in ethanol Φt=0.66, while for acridine orange in glyerol Φt=0.23.
31 citations
TL;DR: In this paper, the isothermal displacement calorimeter was adapted to the measurement of exothermic enthalpies of mixing and results for cyclo-octane + cyclopentane were given.
22 citations
TL;DR: A flow calorimeter with an adjustable throttle, suitable for measurements of the pressure and temperature-dependence of the enthalpy of vapours, is described in this article, where values of (B−T d B d T ), where B is the second virial coefficient, have been derived from the results and analysed together with previous piezometric measurements of B, new piezometrically measured of B reported in an Appendix to this paper, and previous flow-calorimetric measurements of T 2 d 2 Bd T 2.
21 citations
TL;DR: An all-metal enthalpy of wetting calorimeter is described in this paper, which is capable of measuring enthalpies of 10 to 20 J g−1 to an accuracy of better than 1 per cent.
20 citations
TL;DR: In this article, the Calvet microcalorimeter was modified with electroplated thermocouples, reduction in overall size of the calorimeter and equilibration time and mode of initiating the reaction.
Abstract: SUMMARY Our previous work in biochemical calorimetry has been conducted with two modified versions [1, 2] of the Calvet microcalorimeter [3, 4]. The chief features of the modified versions are the use of electroplated thermocouples, reduction in overall size of the calorimeter and equilibration time, and mode of initiating the reaction.
20 citations
TL;DR: Germanium tetraphenyl has been burnt in a rotating, aneroid combustion calorimeter as mentioned in this paper, and the standard heat of combustion was ΔH°c= 3140.2 ± 3.3 kcal mole-1.
Abstract: Germanium tetraphenyl has been burnt in a rotating, aneroid combustion calorimeter. The standard heat of combustion was ΔH°c= 3140.2 ± 3.3 kcal mole–1, which yields a standard heat of formation of ΔH°f(GePh4,c)= 67.2 ± 3.3 kcal mole–1.
20 citations
TL;DR: The heat capacities of Li/NH3 systems having the molecular compositions 1200, 1414, 2040, and 2225% were measured in an adiabatic calorimeter from 60° to 110°K as discussed by the authors.
Abstract: The heat capacities of Li/NH3 systems having the molecular compositions 1200%, 1414%, 2040%, and 2225% were measured in an adiabatic calorimeter from 60° to 110°K Measurements on the 2040% and 2225% solution extended to about 200°K First‐order transitions were observed at 822° and 888°K and the associated heats of transition at each transition temperature were measured for the several compositions Maximum enthalpy change is observed at a composition corresponding to NH3/Li = 415 and is consistent with the proposal that a solid compound, lithium tetrammine, is formed at low temperatures The transition at 822°K is associated with a solid–solid phase transformation in Li(NH3)4 [or Li(NH3)415]; the transition at 888°K is discussed in terms of the equilibria which would have to occur in order to account for the formation of lithium tetrammine
TL;DR: In this paper, the authors used the adiabatic calorimeter to measure the heat capacities of NaCl, KCl and KBr in the temperature range 30 to 500 °C with estimated accuracies of better than ±03% for T less, similar 430 °C and ±05% at the highest temperatures.
Abstract: The adiabatic calorimeter described previously has been improved by automation of the adiabatic shield control. The calorimeter has been used to measure the heat capacities of NaCl, KCl and KBr in the temperature range 30 to 500 °C with estimated accuracies of better than ±03% for T less, similar 430 °C and ±05% at the highest temperatures. The precision of the results, as measured by their average deviation from a smooth curve, is about 015%. Contributions to the heat capacity arising from the thermal creation of vacancies are discussed in relation to the increasing positive curvature of the Cp(T) plots above 600-700 °K. Comparison with the results of ionic conductivity experiments shows that in all three cases the contribution from vacancy formation to the apparent excess Cp is a very small fraction (similar 1%) of the total, which is primarily a higher-order anharmonic effect.
TL;DR: In this article, the heat of respiration of fresh produce in controlled atmosphere (CA) storage was determined with a calorimeter to provide information on the refrigeration load imposed.
Abstract: SUMMARY
—The heat of respiration of fresh produce in controlled atmosphere (CA) storage was determined with a calorimeter to provide information on the refrigeration load imposed. The heat of respiration in air at the same temperature was also measured to enable direct comparison with the heat of respiration in CA. The calorimeter was a heavily insulated Dewar flask and the product was continuously flushed with either air or CA.
The values obtained for the heat of respiration in air were in good agreement with those reported in the literature for these products. The heat of respiration (Btu/Ton-24 hr) in optimum CA with the ratio in CA to that in air given as a percent was as follows: Wando peas at 48°F—6,690, 31%; Thorogreen lima beans—2,290, 30%; cut Victory Golden sweet corn—3,810, 32%; Red Delicious apples—525, 28%. It was concluded that the heat of respiration of fresh produce in CA can be estimated by assuming that it is about 30% that in air.
TL;DR: In this paper, a differential adiabatic calorimeter for the study of heats of transition in solution is described, and demonstrated sensitivity of the apparatus is such that a heat effect of 35 cal/liter occurring over a temperature range of 7°C was determined with a precision of ±2%.
Abstract: A differential adiabatic calorimeter for the study of heats of transition in solution is described. The demonstrated sensitivity of the apparatus is such that a heat effect of 35 cal/liter occurring over a temperature range of 7°C was determined with a precision of ±2%. The results agreed with other reported work. The instrument employs solid state electronics and it may be operated from −10 to 90°C.
TL;DR: In this article, the adiabatic solution calorimeter was designed specifically for thermochemical studies of the less familiar oxidation states of the rare earths, and it has been used in the determination of the heats of solution of the Eu, EuCl2, and Pr(NO3)3 in acids.
Abstract: This adiabatic solution calorimeter was designed specifically for thermochemical studies of the less familiar oxidation states of the rare earths. It has been used in the determination of the heats of solution of Pr, Eu, EuCl2, and Pr(NO3)3 in acids. Currently, it is being employed in the determination of the heats of formation of the various stable, nonstoichiometric oxides of Pr. Close control of adiabatic conditions is maintained automatically throughout a run; manual manipulations are held to a minimum. The calorimeter holds about 200 ml of acid or water into which a solid sample is dissolved at the appropriate time. The temperature of the adiabatic shield which surrounds the calorimeter automatically increases at nearly the same rate as that of the calorimeter itself, and the increment of temperature is measured with a platinum resistance thermometer. The heat generated by a chemical reaction is calculated from a comparison of this rise in temperature to that caused by a calibrated quantity of electr...
TL;DR: The energy of cubic germanium to GeF4 was measured in a bomb calorimeter, and the standard enthalpy of formation, ΔHfo(GeF4,g,298.15 K), was determined to be −(284.57 ± 0.21) kcal mol−1 as discussed by the authors.
TL;DR: In this paper, a deformation calorimeter based on differential thermometry and using a flowing gas stream as a heat transfer medium is described, which allows it to operate under near-isothermal conditions.
Abstract: : The purpose of the paper is to describe a new deformation calorimeter, which is based on differential thermometry and uses a flowing gas stream as a heat transfer medium which allows it to operate under near-isothermal conditions. Also presented are some preliminary test measurements with a crosslinked polyurethane elastomer and crystalline polybutene-1. (Author)
TL;DR: The saturation characteristics of the devices are discussed together with their merits for X-ray measurement and the use of silicon barrier layer and lithium drifted detectors for the measurement of X-rays generated at 10 to 30 kv is described.
Abstract: A description is given of the use of silicon barrier layer and lithium drifted detectors for the measurement of X-rays generated at 10 to 30 kv. Defined X-ray beams are totally absorbed in silicon, and by comparing the charge so produced with the beam energy as measured with a total absorption calorimeter, a value of 3.69+or-0.02 ev per electron-hole pair in silicon is derived. The saturation characteristics of the devices are discussed together with their merits for X-ray measurement.
TL;DR: In this paper, a rotating combustion calorimeter was used to obtain the standard enthalpy of lead tetraphenyl for the organo-metallic compounds of Group IV, which has been used to extend the self-consistent mean bond energy scheme.
TL;DR: The heat capacities of TlCN crystal were measured from 15 to 300°K with an adiabatic calorimeter and three regions of anomalously high heat capacity were discovered.
Abstract: The heat capacities of TlCN crystal were measured from 15 to 300°K with an adiabatic calorimeter. Three regions of anomalously high heat capacity were discovered. Thermodynamic functions of the crystal were calculated by the graphical integration of the heat capacity data. 205Tl nuclear magnetic resonance was observed as functions of temperature and applied static magnetic field. Their second moment values could be interpreted in terms of the anisotropic chemical shift tensor.
TL;DR: In this paper, a calorimeter intended to eliminate systematic errors caused by temperature gradients is presented, with the core completely surrounded by a thermally isolated jacket of equal heat capacity.
Abstract: I HAVE designed a calorimeter intended essentially to eliminate systematic errors caused by temperature gradients. It is a calorimetric body with the core completely surrounded by a thermally isolated jacket of equal heat capacity (Fig. 1). Thermistors imbedded in both body and jacket, to indicate temperatures, form opposite arms of a Wheatstone bridge that is initially balanced when the core and jacket temperatures are at equilibrium. Unbalanced output voltages for small changes in temperature are therefore proportional to the sum of the temperature changes of the core and jacket from equilibrium. The jacket is surrounded by a shield that either remains at a constant temperature, or follows the rising temperature of the jacket, depending on the mode of operation.
TL;DR: In this paper, a differential thermal analysis calorimeter was used in determining the heat capacities of milk fat at −43 and 70 C. The results showed that the heat capacity of the milk fat was.423 cal/g/C (average value) and.521 cal/ g/c (average values) respectively.
Abstract: A differential thermal analysis calorimeter was used in determining the heat capacities of milk fat. The heat capacities of milk fat at −43 and 70 C were .423 cal/g/C (average value) and .521 cal/g/C (average value) respectively.
TL;DR: In this article, the influence of concentration and molecular weight of polystyrene on the heat of dilution with toluene has been examined in detail by use of monodisperse polymers with molecular weights from 900 to 98,000.
Abstract: A calorimeter based on a design by McGlashan has been used to measure the heat of dilution of non-polar polymer–solvent systems. The influence of concentration and molecular weight of polystyrene on the heat of dilution with toluene has been examined in detail by use of monodisperse polymers with molecular weights from 900 to 98,000. The concentration-dependence of χH, the apparent enthalpy parameter, shows characteristics similar to those which have been reported for more polar systems. The concentration-independent enthalpy parameter χ1 varies from –0·32 to –0·02 with increasing molecular weight. The excess and residual entropy of dilution parameters have been calculated and an attempt made to interpret the results.
TL;DR: A digital computer simulation technique is described for designing calorimeters and correcting the output data for heat conduction losses and the design of a small solution calorimeter is given together with the data correction program.
Abstract: A digital computer simulation technique is described for designing calorimeters and correcting the output data for heat conduction losses. The method may be applied to any heat conduction problem. Details of the design of a small solution calorimeter are given together with the data correction program. Theoretical and experimental input functions are compared. Square-wave, exponential, and linear functions are used. Programs are available in either FORTRAN or BASIC. The BASIC program is used with paper punched output data from the calorimeter thermopiles to correct for heat conduction losses. Reactions lasting up to an hour have been followed.
TL;DR: A throttling flow calorimeter has been incorporated into the recycle facility of the Thermal Properties Laboratory in this paper, where energy is added to the expanding gas while it flows through a stainless steel capillary tubing from an insulated resistance wire located inside the entire length of the capillary.
Abstract: A new throttling flow calorimeter has been incorporated into the recycle facility of the Thermal Properties Laboratory Energy is added to the expanding gas while it flows through a stainless steel capillary tubing from an insulated resistance wire located inside the entire length of the capillary The calorimeter is designed to operate at pressures up to 2,000 lb/sqinabs in the temperature range from −240 to +250°F
Data on the isothermal effect of pressure on enthalpy for a mixture containing 5 mole % propane in methane are presented and compared with data from the literature
TL;DR: In this paper, the design and operation of a calorimetric system for the measurement of high temperature enthalpy by the method of mixtures, or ''drop method,'' is described.
Abstract: The design and operation of a calorimetric system for the measurement of high temperature enthalpy by the method of mixtures, or ``drop method,'' is described. Features of the system are (1) an electron beam heated furnace, with sample temperatures determined by optical pyrometry, (2) a copper block calorimeter with calorimeter temperatures obtained by quartz crystal thermometry, and (3) provision for pneumatic acceleration of the sample from the furnace into the calorimeter to minimize heat losses during the transfer. The system has been used to measure the enthalpy of tungsten in the temperature range 1300–1900 K. Values agree with literature data to ±0.5%.
TL;DR: Doses of more than a megarad involve considerable changes in temperature, and allowance must be made for the variation with temperature of the specific heat of carbon.
Abstract: Absorbed-dose calorimeters designed to operate a t less than 100 rads/min need highly sensitive detection of small changes in temperature, and consequently they involve bulky and complex equipment. At high dose rates, on the other hand, such as those often obtainable in beams of energetic electrons, a substantial rise in temperature can be obtained in a short time, making possible a great simplification of the calorimetric method. For example, a dose of 100 k rad to carbon causes a rise in temperature of the order of 1 O C . Owing to the problem of saturation in ion chambers, experiments with relatively large doses are often conveniently done using solid state dosimeters such as colored plastic film, a transparent plastic sheet, or thermoluminescent dosimeters. Calibration of these dosimeters against ion chambers involves an awkward extension beyond the range of dose rates a t which most ion chambers operate efficiently. A simple calorimeter can be used t o calibrate these dosimeters directly in units of absorbed dose. FIGURE 1 shows the construction of such a calorimeter. It consists of a block of carbon 5 cm in diameter by 1 cm thick, embedded in polystyrene foam. The carbon block was made as large as possible consistent with reasonable uniformity of irradiation. This ensures the longest possible thermal time constant. The block is made in two parts cemented together, with a heater (Eureka wire) in the join. A thermistor (Standard Telephones and Cables, type M) is cemented to a carbon rod, which fits closely into the carbon block. This part of the design is similar to that used in a more sensitive instrument described previously. There is a rectangular cavity to take the dosimeter being calibrated, and an additional carbon section fits behind the dosimeter to hold it in place. Thus the dosimeter is placed inside the calorimeter, eliminating the need for a transfer instrument. For doses greater than 10 k rad, the change in resistance of the thermistor can be measured with a simple Wheatstone's bridge and galvanometer, using a 1.5-v'battery. Doses of more than a megarad involve considerable changes in temperature, and allowance must be made for the variation with temperature of the specific heat of carbon. This was measured by performing electrical calibrations over a range of temperatures, with the results shown in FIGURE 2. No dosimeter was included in the calorimeter during these calibrations. 94 1 2
TL;DR: In this paper, a "bench top" microcalorimeter has been designed and constructed for analytical determinations including both inorganic and enzymatic reactions, which can be used to obtain thermodynamic as well as kinetic data simultaneously.
Abstract: A “bench top” microcalorimeter has been designed and constructed. This instrument, and a more conventional microcalorimeter previously described, have been applied to several analytical determinations including both inorganic and enzymatic reactions. Because of the stability, yet rapid equilibration time of the bench top calorimeter, multiple analyses may be performed. The ease of operation, nearly universal applicability, and the possibility of obtaining thermodynamic as well as kinetic data simultaneously, make this technique extremely useful.