Stuart R. Gunn

On the calculation of the corrected temperature rise in isoperibol calorimetry. Modifications of the Dickinson extrapolation method and treatment of thermistor-thermometer resistance values

Rigorous parallel derivations and numerical examples are given for the Dickinson extrapolation method, for a previously described variation, and for a new, more convenient variation. The effect of a changed steady power input (heat of rotation, secondary reaction, or stirring change) is considered. Procedures for the direct use of thermistor resistance values are discussed, and numerical examples are given.

A comparison of standard reactions for solution and combustion calorimetry II. Combustion-calorimeter measurements

Abstract The enthalpy of reaction of tris(hydroxymethyl)-aminomethane ( Tris ) with excess dilute hydrochloric acid has been compared with the enthalpy of reaction of sulfuric acid with excess sodium hydroxide at low and high concentrations. In the following paper, the enthalpy of the H2SO4+NaOH reaction at high concentration has been measured relative to the enthalpy of combustion of benzoic acid. Combination of the results permits deduction of the enthalpies of the H2SO4+dilute NaOH and Tris +HCl reactions, independent of the absolute accuracy of the electrical-heating calibrations of the solution calorimeter.

Detonation Calorimeter and Results Obtained with Pentaerythritol Tetranitrate (PETN)

A bomb calorimeter for measuring the heat of detonation of 25 g charges of high explosive is described. A complete calorimetric measurement can be made in 1 h with a precision of 0.3%. Calorimetric measurements and analysis for PETN are described. The data are interpreted with the aid of thermodynamic and hydrodynamic computer calculations. For unconfined or lightly confined charges, the released energy is largely retained in the products which are shocked considerably off the Chapman‐Jouguet isentrope by reflections from the bomb wall. For heavily confined charges, the energy is largely converted to kinetic and internal energy of the confining case, and the essentially unshocked products expand along the Chapman‐Jouguet isentrope. The products of detonation are found to freeze out at 1500 to 1800°K. The heat of detonation of PETN at 298°K is 1490±6 cal/g, H2O(l).

A calorimetric determination of the specific power and half-life of americium-241

Abstract The specific power output from americium-241 has been determined on two separate samples of americium metal with several calorimeters. The measured specific power of 0·1145 W/g has been used to calculate the half-life of americium-241 as 432·7 ± 0·7 yr. This calorimetric values is significantly different from the half-life of 458·0 yr as determined by absolute alpha (specific activity) low geometry counters as reported in the literature. This new value for americium-241 half-life will change the half-life of plutonium-241 whose half-life calculation is dependent upon the americium-241 half-life. The new beta half-life for plutonium-241 is 14·03 ± 0·30 yr.

Volume‐absorbing calorimeters for high‐power laser pulses

Two types of calorimeters developed to measure energy in high‐power laser pulses are described: solid‐absorber calorimeters, of designs capable of extension to large diameters, and stirrred‐liquid calorimeters. Results are given for measurements of 1.06 μ pulses at power densities up to about 1011 W cm−2. The calorimeters are calibrated by electrical heating; together with measurements of the specular reflection and thermal radiation losses, this permits performance of absolute measurements to an accuracy of better than 1%.

Calorimeters for measurement of ions, x rays, and scattered radiation in laser‐fusion experiments

Several types of calorimeters have been developed for measuring ions, x rays, and scattered radiation produced by fusion experiment targets imploded by laser pulses. One version for ions and x rays uses metal absorbers in a differential arrangement to compensate for the small fraction of scattered laser radiation that is also absorbed; the other version uses a glass absorber which transmits most of the scattered laser radiation. The scattered‐radiation calorimeters use a transparent glass shield to remove ions and x rays and colored glass to absorb the radiation.

Apparent Molar Volumes of Salts and Metals In Liquid Ammonia at 0

Apparent molar volumes of some metals and salts in dilute liquid ammonia solutions at 0° have been measured with a direct‐mixing dilatometer. There is little volume change involved in dissociation of diamagnetic metal species, but a large volume decrease results from dissociation of ion‐pairs in salt solutions. Volumes are estimated for single ions and the solvated electron.

Rocking‐Bomb Calorimeter for Measuring Heats of Solution

A calorimeter designed for measuring the heats of rapid reactions such as dissolution and hydrolysis near room temperature is described. The instrument consists of a sealed copper bomb suspended in an evacuated submarine immersed in a thermostat; stirring is accomplished by rocking the assembly through an arc of 150°. Measurements of the heat of solution of potassium chloride in water at 25.00°C have been performed.

Absence of a Volume Change upon Dilution of Dilute Sodium—Ammonia Solutions at −45° and Potassium—Ammonia Solutions at −34°

Dilatometric measurements of the volume change upon mixing metal—ammonia solutions at concentrations from 0.01 to 0.06N with an approximately equal quantity of pure ammonia have been performed. The observed changes for both sodium solutions at −45° and potassium solutions at −34° are essentially zero throughout the concentration range, and provide no support for existence of sharp minima in the apparent molar volumes at ∼0.02N which have been reported by other workers.

Xenon Tetrafluoride: Heat of Formation

Calorimetric measurements of the heat of reaction of xenon tetrafluoride with aqueous iodide solution give -60 kilocalories per mole for the standard heat of formation, or an average thermochemical bond energy of about 31 kilocalories.