Showing papers on "Calorimeter published in 1974"
01 Sep 1974-Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry
TL;DR: A new type of 3-body calorimeter for measuring absorbed dose produced by ionizing radiation is described in detail, which decreases the effects of thermal gradients and at the same time provides the means to test for these effects.
Abstract: A new type of 3-body calorimeter for measuring absorbed dose produced by ionizing radiation is described in detail. All three bodies rise in temperature during irradiation, and the heat absorbed by the central core is measured by standard means. Only the central core is heated during electrical calibration, but the increased heat losses are compensated by measuring most of the heat lost to the surrounding jacket and automatically adding it to the heat retained by the core. The third body is a massive, thermally-floating shield, whose presence reduces the heat losses during irradiation, with a consequent increase in sensitivity and stability. A mathematical description of the calorimeter behavior is presented, along with a discussion of control and operation technique. In particular, it is shown how this 3-body calorimeter can be calibrated as a 1-body calorimeter, with large heat losses, or as a 2-body calorimeter, in the quasi-adiabatic mode. This calorimeter design decreases the effects of thermal gradients and at the same time provides the means to test for these effects. The results of these tests show that for this particular model, systematic errors caused by thermal gradients, during electrical measurements, are no larger than 0.1 percent. Errors in comparing an electrical run with an irradiation may be somewhat larger because of different temperature gradients within the system. It is also pointed out that the general design of this calorimeter is not restricted to measuring absorbed dose but can be applied to calorimetry in general.
80 citations
TL;DR: In this article, simple theory and techniques are explored and developed to utilize the dif-ferential scanning calorimeter for the determination of heat capacities, glass transition and enthalpies of transition between two thermodynamic states of substances.
79 citations
TL;DR: In this article, an aneroid isoperibol calorimetric apparatus is described which is particularly suitable for measurement of the reaction heat among solids and allows to carry out differential measurements.
58 citations
05 Apr 1974
TL;DR: In this article, a multilayer insulation (MLI) system consisting of 112 unperforated, double-aluminized Mylar reflective shields and 113 water preconditioned silk net spacer pairs was fabricated and installed on a 1.22m (4ft-) diameter calorimeter tank.
Abstract: Experimental and analytical studies were conducted in order to extend previous knowledge of the thermal performance and gas evacuation characteristics of three selected multilayer insulation (MLI) composites. Flat plate calorimeter heat flux measurements were obtained for 20- and 80- shield specimens using three representative layer densities over boundary temperatures ranging from 39 K (70 R) to 389 K (700 R). Laboratory gas evacuation tests were performed on representative specimens of each MLI composite after initially purging them with helium, nitrogen, or argon gases. In these tests, the specimens were maintained at temperatures between 128 K (230 R) and 300 K (540 R). Based on the results of the laboratory-scale tests, a composite MLI system consisting of 112 unperforated, double-aluminized Mylar reflective shields and 113 water preconditioned silk net spacer pairs was fabricated and installed on a 1.22-m-(4-ft-) diameter calorimeter tank.
55 citations
TL;DR: In this paper, the thermal relaxation method is used to measure heat capacities of small samples from 0.060 to 1.2 K. The accuracy was checked by measuring a 2 g copper sample.
Abstract: The thermal relaxation method is used to measure heat capacities of small samples from 0.060 to 1.2 K. The calorimeter incorporates a low heat capacity holder, and is designed to be used in conjunction with a 3He–4He dilution refrigerator. The accuracy was checked by measuring a 2 g copper sample. A least squares fit of the copper data yields a γ value of 0.688 mJ (K2g at.)−1 which agrees to 1.0% with published values of γ for copper. The data exhibit a standard deviation of 5.6% around the fit.
36 citations
CERN1
TL;DR: In this paper, the performance of a liquid-argon ionization chamber, consisting of a set of eigthy 2 mm thick iron plates, is described, and a ratio of 1.2 for the electron-to-proton response is derived.
33 citations
TL;DR: In this paper, the authors measured the heat of formation of Nd/Bi alloys using an isoperibol direct calorimeter and obtained the following values (kcal/g-at): Nd 3 Bi, −15.0±0.7; Nd 5 Bi 3, −22.2± 0.7.
32 citations
TL;DR: In this article, a scanning microcalorimeter for the measurement of energies of transition in solution is described, which utilizes semi-conductor thermoelectric modules and is of a very simple and inexpensive construction.
31 citations
TL;DR: In this paper, four pure explosives and two plastic-bonded explosives covering a wide range of product compositions were fired in a detonation calorimeter, and the results were compared to those calculated with a thermodynamic-hydrodynamic computer code.
29 citations
TL;DR: The best detection for this purpose seems to be a specially constructed 20-100 kΩ thermistor used in conjunction with a new ac lock-in amplifier bridge, which is compared and evaluated with regard to several other types of detectors.
Abstract: A precision thermistor bridge and thermistor is described for use in a thermal titration calorimeter or a high-speed stopped- or continuous-flow calorimeter of the Roughton type. These are compared and evaluated with regard to several other types of detectors, including the platinum resistance thermometer, thermocouple, transistor thermometer, and capacitance thermometers. At this time the best detection for our purpose seems to be a specially constructed 20-100 kΩ thermistor used in conjunction with a new ac lock-in amplifier bridge. The sensitivity of the system is equivalent to a peak-to-peak noise of 25 x 10-6 °C, with a 100-ms time constant and 1 µW power dissipation in the thermistor. Long-term drift of the bridge, without an oven, was 1 x 10-6 °C/min.
18 citations
TL;DR: In this article, an adiabatic scanning calorimeter with a controlled heating rate was made, and the accuracy was found to be within 2% in temperatures ranging from room temperature to 1000K.
Abstract: An adiabatic scanning calorimeter has been made with a controlled heating rate. The sample used was relatively small (3-10g), but the accuracy of the calorimeter was found to be within 2% in temperatures ranging from room temperature to 1000K. It is shown that the temperature distribution in the sample vessel produced in the continuous heating type calorimeter is proportional to the heating rate and inversely proportional to the thermal diffusivity in the sample vessel. An estimate of, and the correction for, the error due to the temperature distribution in the sample vessel has been made. The dehydration reaction of CuSO45H2O was studied, and very sharp, separate, endothermic peaks of the dehydration reaction were obtained.
01 Jan 1974
TL;DR: In the last few years, a large number of state-of-the-art continuous titration calorimeters have been developed as discussed by the authors, which have been used for the measurement of thermodynamic parameters.
Abstract: Calorimeters applicable for the measurement of thermodynamic parameters by the continuous titration technique have existed for about fifteen years. During this time, problems associated with the components of the calorimeter (i.e. constant temperature bath, constant rate buret, reaction vessel, temperature sensing circuit, and data analysis procedure) have gradually been solved so that the continuous titration method now gives results comparable in accuracy to those obtained in conventional solution calorimeters. Inexpensive research quality titration calorimeters have become available commercially in the last few years.
TL;DR: In this paper, the energy of the reaction between F2 and Li2Se to give LiF(c) and SeF6g was measured in a bomb calorimeter.
01 Apr 1974-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: A 15 kva, 450 khz radio-frequency generator was used to levitate and melt yttrium samples ranging from 0.5 to 2 g in an inert atmosphere before being dropped into a copper block drop calorimeter contained in isothermal surroundings as discussed by the authors.
Abstract: A 15 kva, 450 khz radio-frequency generator was used to levitate and melt yttrium samples ranging from 0.5 to 2 g in an inert atmosphere before being dropped into a copper block drop calorimeter contained in isothermal surroundings. The yttrium data were fitted by the following equation where the indicated errors were obtained from the average deviation of the data from the values predicted by the equation:HT−H298.15 = [39.725 ± 0.544] (T − 1799) + [64,116.655 ±163.285] J/mol for 1799
TL;DR: A comparison of the apparent van't Hoff enthalPies with the calorimetrically measured enthalpies shows, that the cooperativity of the system increases continually with rising melting temperatures, and may be approximately described by the model of an all-or-none process.
TL;DR: In this paper, the enthalpies of reaction of the reagents with hydrogen bromide using a steady-state heat flow calorimeter were determined by measuring the enthale of the alkyl and aryl-lithium reagents.
TL;DR: The calorimeter developed in this laboratory for isothermal enthalpy-of-dilution measurements is adapted for use as an adiabatic calorometer for freezing point studies as discussed by the authors.
Abstract: The calorimeter developed in this laboratory for isothermal enthalpy-of-dilution measurements is adapted for use as an adiabatic calorimeter for freezing-point studies. Results are obtained for ethanol solutions in cyclohexane at mole fractions of ethanol from 0.001 up to 0.08. Activities calculated from the results are used to test association models.
TL;DR: In this paper, the heat capacity of gallium arsenide (GaAs) as a function of temperature in the temperature range 3001000K to 1000K was investigated using a differential scanning calorimeter.
Abstract: There is considerable current interest in the electronic properties of the important semiconductor gallium arsenide, but little definitive work has been reported on the thermodynamic properties. There are two conflicting literature reports (7, 3) on the heat capacity of GaAs as a function of temperature in the temperature range 3001000K, both sets of results obtained by use of a drop calorimeter. This note reports corresponding results over the range 310-980K obtained with a differential scanning calorimeter.
Patent•
28 Feb 1974
TL;DR: In this paper, an approach for measuring the mass flow rates of the components comprising a binary gas mixture is provided. This is accomplished by directing a binary fluid or gas through a fluidic humidity sensor and then through a calorimeter which increases the temperature of the flowing binary gas.
Abstract: Apparatus for measuring the mass flow rates of the components comprising a binary gas mixture is provided. This is accomplished by directing a binary fluid or gas through a fluidic humidity sensor and then through a calorimeter which increases the temperature of the flowing binary gas. Electrical signals provided by the fluidic humidity sensor, the flow calorimeter and a power supply which energizes or heats the calorimeter are operated upon in a predetermined manner to provide an output signal indicative of the mass flow rate of one of the binary gases, thus allowing the mass flow rate of the other gas to be determined since the total mass flow rate is previously calculated by the instrument and is the output of operating module 19.
TL;DR: Knowing the radiochemical reactions, the correspondingG-values and the energy of chemical bonds changed, it is possible to calculate the value of the heat defect, which was found to be rather close to the value measured in some plastics.
Abstract: The amount of energy absorbed in material and not converted to heat is identical with the (negative or positive) heat of reactions and other processes induced by radiation. This fraction of energy is called “heat defect”. In order to determine the heat defect, which is generally a very small effect, a precise isothermal twin calorimeter was constructed [description see Sabelet al., Rad. and Environm. Biophys.11, 247–257 (1974)]. One of the absorbers consisted of the material to be investigated.
TL;DR: In this paper, the heat capacity of four ferrites with the chemical composition Ni1-xZnxFe2O4 (x = 0.5, 0.64), Mn1−x Znx Fe2O 4 (x= 0.42), and BaFe12O19 has been measured with a Nernst adiabatic calorimeter in the temperature range 80 to 303 °K.
Abstract: The heat capacity of four ferrites with the chemical composition Ni1–xZnxFe2O4 (x = 0.5, 0.64), Mn1–xZnxFe2O4 (x = 0.42), and BaFe12O19 has been measured with a Nernst adiabatic calorimeter in the temperature range 80 to 303 °K. The heat capacity has been found to decrease with decreasing temperature. The Debye temperatures have been calculated and compared with those obtained from elastic data.
Die Warmekapazitaten von vier Ferriten mit den chemischen Zusammensetzungen Ni1–xZnxFe2O4 (x = 0.5; 0.64), Mn1–xZnxFe2O4 (x = 0,42) und BaFe12O19 wurden mit einem adiabatischen Nernst-Kalorimeter, im Temperaturbereich 80 bis 303 °sK gemessen. Es wurde gefunden, das die Warmekapazitat mit abnehmender Temperatur abnimmt. Die Debye-Temperaturen wurden berechnet und mit denen aus elastischen Daten verglichen.
TL;DR: In this article, the CSIRO ground heat flux plates were recalibrated in situ using a simple calorimeter and the thermal capacity of the soil was determined simultaneously in the laboratory.
TL;DR: In this paper, a new calorimeter for measuring excess enthalpies of liquid mixtures is described, where volume changes on mixing are accommodated by a teflon diaphragm separating the liquids from an air space.
IBM1
TL;DR: The Perkin-Elmer DSC-lB differential scanning calorimeter as discussed by the authors is a relatively standard laboratory instrument and it is possible to improve the operation significantly with a few simple modifications.
01 Jun 1974
01 Oct 1974
TL;DR: In this paper, a method of reducing the r.f.d.c. substitution error in calorimeter-type waveguide power meters by the use of two thermometers is presented.
Abstract: This paper presents a method of reducing the r.f.-d.c. substitution error in calorimeter-type waveguide power meters by the use of two thermometers. A calorimeter for the frequency range 60 - 90 GHz based on this principle is described.
TL;DR: After knowing the heat defect in the different kinds of absorber substances it is possible to construct an absolute dose calorimeter with a precision given by the accuracy of the value for the heat defects.
Abstract: The paper describes the construction and function of an isothermal twin calorimeter for the measurement of the fraction of absorbed energy of X-rays which is not converted to thermal energy (heat). This fraction, the „heat defect“ must be known in absolute dose calorimetry, since the calorimetrically measured absorbed dose in a given substance is too low by the value of the heat defect for the radiation and the substance used.
TL;DR: In this article, the enthalpy changes of solutions and reactions with aqueous KCN solution of Zeise's salts, K[PtCl3(olefin), were measured using a twin-type calorimeter.
Abstract: Using a twin-type calorimeter, the enthalpy changes of solutions and reactions with aqueous KCN solution of Zeise’s salts, K[PtCl3(olefin)], were measured. As ligand olefins, ethylene, propylene, 1-butene, 1-pentene, and 1-hexene were employed. It was estimated from a thermochemical analysis that the order of strength of platinum-olefin bonding is as follows; K[PtCl3(C3H6)]\gtrsimK[PtCl3(C3H6)]\gtrsimK[PtCl3(1-C6H12)]\gtrsimK[PtCl3(1-C4H8)]\gtrsimK[PtCl3(1-C5H10)]. This order was compared with the data of infrared spectra and both the results coincide with each other.