Heat capacity of dispersed rocks

Protection of automobile roads from negative cryogenic processes is a current issue to which significant attention is devoted in both scientific and engineering communities. In many cases important for practice, the the thermal factor determines the reliability and security of the use of the road in the cryolithic zone. The heat capacity of dispersed rocks is among the most important indicators of the physical properties determining the intensity of thermal processes in the road surfaces and road foundations. The precision of determination of the total heat capacity of the rocks in thawed and frozen state largely determines the precision of the forecast of the thermal regime of roads in the cryolithic zone. A complex assessment of the impact of ice content of the dispersed rocks on the value of total heat capacity was done. 2D and 3D charts which allow to assess the possible range of change in the heat capacity of the dispersed rocks in thawed and frozen state, in both a wide range and in the typical range of values, were produced. Among the main criteria determining the extent of the seasonal freezing and thawing of the soils of the active layer is the Stefan number, a dimensionless criterion. An overall assessment of the impact of ice content on the ground (rock) foundations of the roads and of the air temperature in the warm period of the year on the quantitative values of the Stefan number was done. Charts allowing to determine in both a wide and typical range the changes of values of the Stefan numbers, permitting to assess the possible range of changes of the Stefan number, were made. It was determined, in particular, that for the typical dispersed rocks of the road foundations in the cryolithic zone the range of change in the Stefan numbers is 2.1-6.5.

Novel nanoparticle catalysts for catalytic gas sensing

Applications such as catalytic gas sensing require a high density of catalytically active sites at low total heat capacity. One way to achieve this goal is the molecular linkage of colloidal nanoparticles with bifunctional ligands resulting in 3D-porous networks. The catalytic properties of such structures were investigated in a thermoelectric hydrogen sensor.

The heat capacities of acetone, methyl iodide and mixtures thereof in the liquid state

The heat capacities of liquid mixtures of acetone and methyl iodide of various compositions have been determined at atmospheric pressure in the temperature range — 20 to 35 °C. The corresponding compressibilities have also been measured, and the heat capacities at constant volume determined as functions of the temperature and volume. The heat capacities increase on isothermal compression, and with rising temperature at constant volume. Resolution of the total heat capacity into its many components shows that the configurational contribution to the heat capacity at the melting point is R cal mole -1 deg -1 for methyl iodide and about 2 R cal mole -1 deg -1 for acetone. The excess heat capacity at constant volume over that estimated on an additivity basis is small, and rises with a rise in temperature to about 3 % of the total value a t 35 °C. A comparison of the present data with those relating to the acetone + chloroform system indicates that compound formation is less likely in the acetone + methyl iodide system .

The heat capacities of certain liquids

The heat capacities and adiabatic compressibilities of carbon tetrachloride, chloroform, methylene dibromide and m ethyl iodide have been measured between about — 30 and 30° C. The heat capacities at constant volume have been derived, and it is emphasized th a t these quantities apply to particular volumes existing at different temperatures. An isotherm for liquids, based on high-pressure data, has been used to obtain an expression for the effect of change of volume on the heat capacity at constant volume. This relation has been applied to mercury, carbon disulphide, carbon tetrachloride, chloroform and water. Satisfactory agreement has been obtained with the results found in other ways by Bridgman (1911, 1912) on mercury and water and by Gibson & Loeffler (1941) on carbon tetrachloride and water. From the results found in this work on the resolution of the various energy contributions to the liquid heat capacities of polyatomic molecules other than water, it is concluded that the concept of molecular rotation about a preferred axis can explain most of the facts established. There remains, however, a structural contribution to the total heat capacity which is approximately R cal mole -1 deg. -1 .