Properties of aqueous solutions of lithium and calcium chlorides: formulations for use in air conditioning equipment design

The possible role of ammonia in a future energy infrastructure is discussed. The review is focused on the catalytic decomposition of ammonia as a key step. Other aspects, such as the catalytic removal of ammonia from gasification product gas or direct ammonia fuel cells, are highlighted as well. The more general question of the integration of ammonia in an infrastructure is also covered.

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Ammonia as a possible element in an energy infrastructure: catalysts for ammonia decomposition

Crystallization of sodium sulfate phases in porous materials: The phase diagram Na2SO4–H2O and the generation of stress

Recent Work in the Field of High Pressures

Crystallization pressure of salt crystals growing in confined pores is found to be the main cause for damage to stone and masonry. In this work, the crystallization of sodium sulfate salts in Cordova Cream and Indiana limestones is investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The DSC experiments indicate that sodium heptahydrate always precipitates prior to the decahydrate (mirabilite), at a temperature between 15 and 7°C in the selected stones. The threshold supersaturation for the nucleation of heptahydrate is less than 2. In constrast, mirabilite precipitates close to or below 0°C and its crystallization pattern is completely different: precipitation takes place abruptly when the threshold supersaturation is reached, which is greater than 7. Indeed, the DSC and the DMA experiments reveal the rare nature of the nucleation of mirabilite for the investigated stones. The crystallization pressure exerted by heptahydrate does not cause damage under the conditions of the cooling experiments. In contrast, mirabilite exerts a very high crystallization pressure on the pore wall causing damage of the stone; moreover, the transient stress can remain for a long period of time since the relaxation process is slow.

Crystallization of sodium sulfate salts in limestone

It was shown in a recent paper on “ The Decomposition of Ammonia by Heat,”* that ammonia is decomposed almost (if not quite) completely when heated in a porcelain vessel at about 800° to 1100°, and that there is no sign of equilibrium between the ammonia and its decomposition products at any of the temperatures employed, 677° to 1111°. In order to discover if there is any such state of equilibrium, it was thought better to attempt to reach that state by synthesising ammonia instead of decomposing it, as the testing for and estimation of the ammonia could then be carried out with much greater accuracy.

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The Direct Synthesis of Ammonia

The dissociation of sodium sulphate decahydrate

In an earlier communication, Perman and Urry described the measurement, by a direct method, of the compressibility coefficients of aqueous solution of urea, cane sugar, potassium chloride, and calcium chloride, over a range temperatures and concentrations. Their work was over the pressure range 0-200 atmospheres excess pressure. They were able to apply their together with other data obtained by their co-workers, to an extension Porter's theory of compressible solutions, and thus obtained values for osmotic pressures of those solutions which agreed very well with the obtained by more direct methods. The present work is a continuation of this and subsequent work (unpublished) by these authors. It was intended, especially, to investigate the effect of nature of the solute molecule upon the compressibility, and, for this reason the choice of solutes was particularly important. A number of series chemically related compounds were used where only one part of the mole varied in a progressive manner from substance to substance. In series there was no chemical relationship, but the members had the empirical formula and their molecular weights were therefore simple multi of each other.

The Compressibility of Aqueous Solutions

This work was originally undertaken in order to obtain an accurate value for the density of ammonia, the only determination that appeared reliable being that of Le Duc. While the experiments were in progress, the result of a determination by Guye was published; the number differed from that of Le Due and made a fresh determination still more desirable. We have now determined the density at temperatures ranging from -20° to +100°C., also the density at half an atmosphere pressure at 0°C. From these data the coefficient of expansion and the compressibility can be calculated. In addition to this, measurements of the pressure coefficient, of vapour-pressure, and of the density of ammonia in the presence of air, have been made.

Some Physical Constants of Ammonia: A Study of the Effect of Change of Temperature and Pressure on an Easily Condensible Gas

Much doubt has recently existed as to the interpretation which may be put upon measurements of the velocity of chemical change in gas reactions. Van’t Hoff deduced the “order of the reaction” in certain cases from considerations of the law of mass action. Bone and Wheeler have shown that the combination of hydrogen and oxygen at temperatures below that necessary to explode the mixture takes place mostly (if not entirely) at the surfaces with which the gases are in contact, and that no conclusion as to the order of the reaction can be drawn from pressure measurements. Ozone was chosen for further work on the subject, as it affords one of the simplest possible cases. The decomposition by heat furnishes only one substance, and the reaction is irreversible (at least for all practical purposes).

Edgar Philip Perman

Papers

The Direct Synthesis of Ammonia

The dissociation of sodium sulphate decahydrate

The Compressibility of Aqueous Solutions

Some Physical Constants of Ammonia: A Study of the Effect of Change of Temperature and Pressure on an Easily Condensible Gas

The Decomposition of Ozone by Heat