TERNARY COMPOUNDS IN THE SYSTEM NH3–H2O2–H2O

1959 ◽  
Vol 37 (12) ◽  
pp. 2064-2067 ◽  
Author(s):  
Paul A. Giguère ◽  
David Chin
Keyword(s):  
Thermal Analysis ◽  
Hydrogen Peroxide ◽  
Melting Point ◽  
Latent Heat ◽  
Heat Of Fusion ◽  
Latent Heat Of Fusion ◽  
Component System ◽  
Degree Of Dissociation ◽  
Ternary Compounds ◽  
Anhydrous Ammonia

A thermal analysis of the three-component system ammonia–hydrogen peroxide –water was carried out by adding anhydrous ammonia to the hydrate H2O2•2H2O. A first compound was found, with formula NH3•3H2O2•6H2O, melting at −23.9 °C; another compound melting around 15° appears to be a hydrate of ammonium peroxide, (NH4)2O2•2H2O. The eutectics are at −54.5°, 0.7% NH3, and −33.4°, 12.5% NH3. Careful redeterminations have confirmed that the melting point of the hydrate H2O2•2H2O is −52°, not −50° as was sometimes claimed. The latent heat of fusion of that compound is estimated to be 3.9 kcal and the degree of dissociation on melting, about one-third.

scholarly journals Development of Binary Eutectic Organic Phase Change Materials for Solar Thermal Energy Storage Systems

2019 ◽  
Vol 9 (2) ◽  
pp. 2207-2210
Keyword(s):  
Energy Storage ◽  
Melting Point ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Thermal ◽  
Heat Of Fusion ◽  
Solar Thermal Energy ◽  
Latent Heat Of Fusion ◽  
High Latent Heat

Solar thermal energy storage unit anchored fatty acids as Phase Change Materials (PCMs) having narrow range of transition temperature and high latent heat of fusion. In this paper, a new novel eutectic PCM was developed by using a fatty acid (acetamide) and non-paraffin organic PCM (acetanilide) for a sharp melting point and high latent heat of fusion. The optimized eutectic PCM may be used for middle temperature range solar thermal energy storage systems. The binary mixture of acetamide and acetanilide at various compositions by mass ratio (wt%) was prepared and optimized experimentally for lowest value of melting point at a eutectic mixture composition of 60 wt% of acetamide and 40 wt% of acetanilide. Eutectic PCM was analyzed by Differential Scanning Calorimetry (DSC) and Field-Emission Scanning Electron Microscopy (FE-SEM). DSC results revealed that optimized eutectic PCM has a sharp melting point of 65.37°C and high latent heat of fusion of 224.67 kJ/kg. Accelerated thermal cycle testing of optimized eutectic PCM was performed for 100 melting and freezing cycles and change in melting temperature and latent heat of fusion was acceptable.

The specific heats below 320°K of potassium, rubidium and caesium

1965 ◽  
Vol 284 (1396) ◽  
pp. 83-107 ◽  
Keyword(s):  
Melting Point ◽  
Specific Heat ◽  
Latent Heat ◽  
Slow Release ◽  
Heat Of Fusion ◽  
Additional Contribution ◽  
Thermal Generation ◽  
Latent Heat Of Fusion ◽  
Specific Heats ◽  
Increasing Temperature

The specific heat of potassium has been measured in the range 0·4 to 26°K and the specific heats of rubidium and caesium in the range 0·4 to 320°K. Previously reported specific heat anomalies in the range 100 to 300°K were not confirmed. The θ c 0 and γ values were estimated as 90·6 +1·4 -0·3 °K and 497 ± 20 μ cal degK -2 gatom -1 for potassium, as 55·6 ± 0·5°K and 576 +70 -40 μ cal degK -2 gatom -1 for rubidium and as 38·4 ± 0·6°K and 764 ± 250 μ cal degK -2 gatom -1 for caesium. A slow release of energy (~ 1 μ cal s -1 gatom -1 ), dependent on thermal history, was observed from rubidium and caesium in the region of 4°K and may correspond to the annealing out of defects introduced by plastic strain on cooling. Positive anharmonic contributions to the specific heat are evident at high temperatures and an additional contribution to the specific heat, of the form (e - E / RT /T 2 ), becomes apparent from about 50°K below the melting point and may be identified with the thermal generation of lattice vacancies. The melting point of pure rubidium is estimated as 312·65 ± 0·01°K and the latent heat of fusion as 524·3 ± 1·0 cal/gatom. For caesium the melting point is 301·55 ± 0·01°K and, with some assumptions, the latent heat is 498·9 ± 0·5 cal/gatom. For both metals the specific heat of the liquid decreases with increasing temperature.

scholarly journals The variation with temperature of the specific heat of sodium in the solid and the liquid state; also a determination of its latent heat of fusion

1914 ◽  
Vol 89 (614) ◽  
pp. 561-574 ◽  
Keyword(s):  
Melting Point ◽  
Specific Heat ◽  
Latent Heat ◽  
Liquid State ◽  
Mean Value ◽  
Heat Of Fusion ◽  
Latent Heat Of Fusion ◽  
The Mean ◽  
Considerable Range

The present paper contains the results of an investigation into the variation, with temperature, of the specific heat of sodium in the solid and the liquid state; also, some determinations of its latent heat of fusion. Our knowledge of the variations of the specific heat of metals in the region of their melting point is extremely vague and hypothetical, since the methods of investigation commonly employed are only capable of giving the mean value of the specific heat over a considerable range of temperature.

Determination of the latent heat of fusion and solid fraction evolution of metals and alloys by an improved cooling curve analysis method

2019 ◽  
Vol 140 (4) ◽  
pp. 1825-1836 ◽  
Author(s):  
Carlos González-Rivera ◽  
Anthony Harrup ◽  
Carla Aguilar ◽  
Adrián M. Amaro-Villeda ◽  
Marco A. Ramírez-Argáez
Keyword(s):  
Latent Heat ◽  
Solid Fraction ◽  
Metals And Alloys ◽  
Curve Analysis ◽  
Cooling Curve ◽  
Heat Of Fusion ◽  
Analysis Method ◽  
Latent Heat Of Fusion ◽  
Cooling Curve Analysis

Measurement and Modeling of Latent Heat Release During Freezing of Aqueous Solutions in a Small Container

2000 ◽  
Author(s):  
Ramachandra V. Devireddy ◽  
John C. Bischof ◽  
Perry H. Leo ◽  
John S. Lowengrub
Keyword(s):  
Mass Transport ◽  
Heat Release ◽  
Latent Heat ◽  
Pure Water ◽  
Heat Of Fusion ◽  
Freezing Process ◽  
Latent Heat Release ◽  
Aqueous Systems ◽  
Heat And Mass Transport ◽  
Latent Heat Of Fusion

Abstract The latent heat of fusion, ΔHf of a cryobiological medium (a solute laden aqueous solution) is a crucial parameter in the cryopreservation process. The latent heat has often been approximated by that of pure water (∼ 335 mJ/mg). However, recent calorimetric (DSC - Pyris 1) measurements suggest that the actual magnitude of latent heat of fusion during freezing of solute laden aqueous systems is far less. Fourteen different pre-nucleated solute laden aqueous systems (NaCl-H2O, Phosphate Buffered Saline or PBS, serum free RPMI, cell culture medium, glycerol and Anti Freeze Protein solutions) were found to have significantly lower ΔHf than that of pure water (Devireddy and Bischof, 1998). In the present study additional calorimetric experiments are performed at 1, 5 and 20 °C/min in five representative cryobiological media (isotonic or 1× NaCl-H2O, 10× NaCl-H2O, 1× PBS, 5× PBS and 10× PBS) to determine the kinetics of ice crystallization. The temperature (T) and time (t) dependence of the latent heat release is measured. The experimental data shows that at a fixed temperature, the fraction of heat released at higher cooling rates (5 and 20 °C/min) is lower than at 1 °C/min for all the solutions studied. We then sought a simple model that could predict the experimentally measured behavior and examined the full set of heat and mass transport equations during the freezing process in a DSC sample pan. The model neglects the interaction between the growing ice crystals and is most appropriate during the early stages of the freezing process. An examination of the coefficients in the heat and mass transport equations shows that heat transport occurs much more rapidly than solute transport. Hence, the full model reduces to one in which the temperature profile is constant in space while the solute concentration profile obeys the full time and space dependent diffusion equation. The model reveals the important physical parameters controlling the mass transport at the freezing interface and further elucidates the experimental results, i.e. the temperature and time dependence of the latent heat release.

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