Heat of transformation of chains in amorphous sulphur

1997 ◽  
Vol 50 (3) ◽  
pp. 517-519
Author(s):  
W. Swiatkowski
Keyword(s):  
Heat Of Transformation

scholarly journals X-ray investigation of the structure transition of methane at the λ point

1939 ◽  
Vol 171 (947) ◽  
pp. 569-578 ◽  
Keyword(s):  
Crystal Structure ◽  
Specific Heat ◽  
Structure Transition ◽  
Sharp Maximum ◽  
Critical Range ◽  
Other Substances ◽  
Strong Resemblance ◽  
Transition Points ◽  
Λ Point ◽  
Heat Of Transformation

A great deal of work has been done on the crystal structure of long-chain hydrocarbons and their behaviour near transition points. These transitions are as a rule quite normal, in so far as the transition is marked by the liberation or binding of a definite heat of transformation and change in structure. The simplest of the hydrocarbons, methane, shows a change from the ordinary behaviour. At 20.4° K a so-called transition of the second kind (Clusius and Perlick 1933) takes place, of which an abnormal rise of the specific heat is typical. This begins at low temperatures where the specific heat rises at first slowly to reach a very sharp maximum at 20.4° and then falls abruptly to somewhat normal values. No latent heat appears. The effect bears a strong resemblance to the λ point of helium and other substances. The crystal structure of methane has been directly determined by two authors (McLennan and Plummer 1929; Mooy 1931) of whom only Mooy paid special attention to any possible change of structure at the transition point. He observed no change in the critical range. The structure is cubic face-centred according to both authors, but we would like to point out that Mooy’s table contains two lines which do not belong to reflexions from that lattice and which he labelled “parasitic lines”.

The specific heat of lithium from 20 to 300 °K: the martensitic transformation

1960 ◽  
Vol 254 (1279) ◽  
pp. 444-454 ◽  
Keyword(s):  
Martensitic Transformation ◽  
Specific Heat ◽  
Atomic Weight ◽  
Phase Region ◽  
Two Phase ◽  
Self Diffusion ◽  
Debye Temperatures ◽  
Order Of Magnitude ◽  
Two Phases ◽  
Heat Of Transformation

Measurements on lithium of atomic weight 6·945 are reported. A thermal study of the martensitic transformation showed a large specific-heat anomaly in the reversion region and a specific heat dependent upon thermal history in the two-phase region. The high-temperature end of the reversion anomaly shows time effects which suggest that the process here is controlled by a spectrum of activation energies of the same order of magnitude as that for self diffusion. With some assumptions the heat of transformation from hexagonal closepacked to body-centered cubic lithium is deduced to be about 14 cal/g atom and the Debye temperatures of the two phases at 60 °K are 390 and 371 °K respectively. The entropy at 298·15 °K is 6·95 ±0·04 cal/°K g atom.

Phase Transformation of Hexacelsians Doped with Li, Na and Ca

2005 ◽  
Vol 494 ◽  
pp. 107-112 ◽  
Author(s):  
V. Dondur ◽  
R. Dimitrijević ◽  
A. Kremenović ◽  
Lj. Damjanović ◽  
M. Kićanović ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Thermal Treatment ◽  
Maximum Temperature ◽  
29Si Mas Nmr ◽  
Thermally Induced ◽  
Synthesis Conditions ◽  
Nmr Method ◽  
Lta Zeolite ◽  
Dsc Method ◽  
Heat Of Transformation

A series of hexacelsians with different compositions were synthesized by thermally induced transformation of a LTA zeolite. Various forms of hexacelsians have been characterized by XRPD, IR, Raman and 29Si MAS NMR method. The phase transformation ab hexacelsian was investigated by DSC method. This phase transformation is sensitive to synthesis conditions, doping and thermal treatment. The peak maximum temperature, Tm, varies from 302 up to 353 oC. Heat of transformation changes from 0.42 to 1.77 kJ/mol.

scholarly journals VII. On the specific heat and heat of transformation of the iodide of silver, Agl, and of the alloys Cu 2 I 2 .AgI, Cu 2 I 2 .2AgI, Cu 2 I 2 .3AgI,Cu 2 I 2 .4AgI, Cu 2 I 2 .12AgI, PbI 2 .AgI

1883 ◽  
Vol 34 (220-223) ◽  
pp. 104-105 ◽  
Keyword(s):  
Specific Heat ◽  
Calorimetric Investigation ◽  
Heat Of Transformation

The authors’ calorimetric investigation refers to substances which have been already studied by Mr. G. F. Rodwell (“ Proc. Roy. Soc.” vol. 32) as to their expansion and contraction by heat. After having detailed the method of experimenting and tabulated the results of determinations for each substance, the authors recapitu­late the results in the following table

The specific heat of sodium from 20 to 300 °K: the martensitic transformation

1960 ◽  
Vol 254 (1279) ◽  
pp. 433-443 ◽  
Keyword(s):  
Martensitic Transformation ◽  
Specific Heat ◽  
Phase Region ◽  
Two Phase ◽  
Cast Sample ◽  
Hexagonal Close Packed ◽  
Debye Temperatures ◽  
Significant Difference ◽  
Two Phases ◽  
Heat Of Transformation

Measurements on a cast sample and an extruded sample are reported. There is no significant difference in behaviour. No anomaly of the type reported by Dauphinee et al. (1954) was found. A thermal study of the martensitic transformation showed a large specific-heat anomaly in the reversion region and a specific heat dependent on thermal history in the two-phase region. The heat of transformation from hexagonal close-packed to body-centred cubic sodium is deduced to be about 10 cal/g atom and the Debye temperatures of the two phases at 20 °K to be 160 and 153 °K respectively. The entropy at 298.15 °K is 12.24 ± 0.12 cal/°K g atom.

Thermodynamics of Shrinkage of Fibrous (Racked) Rubber

1958 ◽  
Vol 31 (3) ◽  
pp. 485-498
Author(s):  
J. F. M. Oth ◽  
P. J. Flory
Keyword(s):  
Tensile Force ◽  
The Other ◽  
Degree Of Crystallinity ◽  
Melting Point Depression ◽  
Heat Of Fusion ◽  
Γ Radiation ◽  
Melting Temperatures ◽  
The Degree Of Crystallinity ◽  
Heat Of Transformation

Abstract Highly oriented natural rubber samples of Roberts and Mandelkern, prepared by racking and subsequently crosslinked using γ-radiation, undergo a spontaneous shrinkage upon melting which closely resembles the shrinkage of collagen. If the transformation is arrested by application of a tensile force, a state of equilibrium may be established between two distinct zones, or phases, one being totally amorphous (shrunken) and the other unchanged (i.e., racked). Determination of the stress τeq required for phase equilibrium at various temperatures is described. Extrapolation to τeq=0 gives equilibrium melting temperatures Tmi, which are about 8° below the temperatures Tsi for spontaneous shrinkage. The heat of transformation of racked to amorphous rubber calculated from the dependence of τeq on T is 4.5 cal g−1. Since the degree of crystallinity is only 0.24, the heat of fusion calculated for 1 g of crystalline rubber is ca. 19 cal, which agrees satisfactorily with the value 15.3 cal, deduced by Roberts and Mandelkern through use of the melting point depression method. The shrinkage of racked rubber displays all of the important features associated with the similar contraction of fibrous proteins.

Specific heat of sodium nitrate and silver nitrate by medium high temperature adiabatic calorimetry

1967 ◽  
Vol 20 (1) ◽  
pp. 1 ◽  
Author(s):  
VC Reinsborough ◽  
FEW Wetmore
Keyword(s):  
Specific Heat ◽  
Silver Nitrate ◽  
Sodium Nitrate ◽  
Thermal Hysteresis ◽  
Adiabatic Calorimeter ◽  
Drop Calorimetry ◽  
Calorimetric Technique ◽  
Temperature Ranges ◽  
Solid Liquid ◽  
Heat Of Transformation

��� A relatively simple adiabatic calorimeter for use in the temperature range 50-350� was constructed and used to measure the specific heat of sodium nitrate from 150 to 300� and silver nitrate from 70 to 250�. Each salt undergoes a solid-solid and a solid-liquid transformation in these temperature ranges. The Cp values for sodium nitrate agreed within the calculated experimental error of �0.2% with those of Sokolov and Shmidt1 but the silver nitrate showed a large discrepancy with those of Janz and Kelly2 obtained by drop calorimetry for the 160-210� region, where thermal hysteresis may have occurred in the drop calorimetric technique. The heat of transformation for the solid-solid transition in silver nitrate at 159.4� was found to be 561�4 cal mole-1.

XXVII. On the specific heat and heat of transformation of the iodide of silver, AgI, and of the alloys, or compounds, Cu 2 I 2 . AgI; Cu 2 I 2 . 2AgI; Cu 2 I 2 . 3AgI; Cu 2 I 2 . 4AgI; Cu 2 I 2 . 12AgI; PbI 2 . AgI

1882 ◽  
Vol 173 ◽  
pp. 1169-1176 ◽  
Keyword(s):  
Specific Heat ◽  
Temperature Change ◽  
Silver Iodide ◽  
Colour Change ◽  
Calorimetric Study ◽  
Copper Iodide ◽  
Lead Iodide ◽  
Quantity Of Heat ◽  
Heat Of Transformation

In a series of papers printed in the Proceedings of the Boyal Society for the years 1877, 1879, 1881, Mr. G. F. Rodwell has investigated the expansion and contraction by heat of the silver iodide, AgI; of certain chlorobromiodides of silver; and of certain alloys of silver iodide, with lead iodide, and copper iodide. Analogous researches were made by us on the substances HgI 2 . 2AgI; HgI 2 . 3AgI; HgI 2 . Cu 2 I 2 ;* which, when heated to a certain temperature, change their colour. HgI 2 . 2AgI and HgI 2 .3AgI, at about 50° C., change from canary-yellow to red, and HgI 2 . Cu 2 I 2 , at about 70° C., changes from red to a chocolate colour. For temperatures below and beyond the colour-change the co-efficient of expansion and the specific heat are regular, but during a range of a certain number of degrees of heat in which colour-change and corresponding modification of structure take place, the substances undergo a very notable expansion and absorb a great quantity of heat. It seemed to Mr. Rodwell, and to us, that it would be interesting to make a calorimetric study of those substances whose expansion and contraction he had determined, and Mr. Rodwell having kindly furnished us with the specimens which he employed in his researches, we have briefly described in this paper the method and results of our calorimetric determinations.

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