scholarly journals The ratio of the specific heats of nitrogen and of oxygen

1924 ◽  
Vol 105 (730) ◽  
pp. 225-243 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Large Volume ◽  
Ideal Gas ◽  
Absolute Temperature ◽  
Specific Heats ◽  
Previous Communication ◽  
Free Air ◽  
Before And After ◽  
The Absolute

The investigation of the ratio of the specific heats, c p / c v = γ , of nitrogen and oxygen described in the following paper was undertaken by a method substantially the same as that used previously with air and carbon dioxide, and described in an earlier communication. This consists in measuring the fall in temperature which occurs when a large volume of the gas is allowed to expand adiabatically. If a vessel filled with the gas at a pressure p 1 , slightly greater than atmospheric, is put into communication with the free air, at a pressure p 2 , by suitable means, so that the equalisation of pressures occurs as nearly as possible adiabatically, and if T 1 and T 2 are the absolute temperature of the gas before and after expansion, then, for an ideal gas , it is known that γ = c p /c v = log p 1 - log p 2 /(log p 1 - log p 2 ) - (log T 1 - log T 2 ) (1) Before considering the details of the method used in the present research reference may be made to the experiments of Mercer, in 1914, and of Shields, in 1917, supplementing the work discussed in the previous communication.

The specific heats of three paramagnetic salts at very low temperatures

1956 ◽  
Vol 237 (1210) ◽  
pp. 395-403 ◽  
Keyword(s):  
Specific Heat ◽  
Absolute Temperature ◽  
Magnesium Nitrate ◽  
Paramagnetic Resonance ◽  
Specific Heats ◽  
Ammonium Alum ◽  
Relaxation Measurements ◽  
Ferric Ammonium ◽  
The Absolute ◽  
Measured Specific Heat

The specific heats of three paramagnetic salts, neodymium magnesium nitrate, manganous ammonium sulphate and ferric ammonium alum, have been measured at temperatures below 1°K using the method of γ -ray heating. The temperature measurements were made in the first instance in terms of the magnetic susceptibilities of the salts, the relation of the susceptibility to the absolute temperature having been determined for each salt in earlier experiments. The γ -ray heatings gave the specific heat in arbitrary units. The absolute values of the specific heats were found by extrapolating the results of paramagnetic relaxation measurements at higher temperatures. The measured specific heat of neodymium magnesium nitrate is compared with the value calculated from paramagnetic resonance data, and good agreement is found.

The nuclear specific heat in paramagnetic cupric salts at temperatures below 1° K I. Thermodynamic measurements made from a study of the field-dependence of the adiabatic susceptibility

1950 ◽  
Vol 203 (1074) ◽  
pp. 375-391 ◽  
Keyword(s):  
Magnetic Susceptibility ◽  
Specific Heat ◽  
Field Dependence ◽  
Absolute Temperature ◽  
Potassium Sulphate ◽  
Specific Heats ◽  
Magnetic Cooling ◽  
Thermodynamic Measurements ◽  
Small Fields ◽  
The Absolute

Thermodynamic measurements have been made at temperatures below 1°K, obtained by the method of magnetic cooling, on copper potassium sulphate and on a diluted copper Tutton salt. A study has been made of the field- dependence (for small fields) of the adiabatic susceptibility of the cooled and thermally isolated salt, the measurements covering the range of temperature from 1°K down to 0.05°K for copper potassium sulphate, and to 0.025° K for the dilute salt. From these measurements the entropy and magnetic susceptibility are determined as functions of the absolute temperature. It is concluded that for both salts the susceptibility follows a Curie-Weiss law, the values of ∆ being 0.034 and 0.0048º K respectively; the specific heats are of the form ∆ / T 2 , the values found for A being 6.1x10 -4 R for copper potassium sulphate and 1.98x10 -4 R for the dilute salt.Deviations from this behaviour in a ferromagnetic direction are found for copper potassium sulphate below 0.07° K.

scholarly journals III. On the specific heats of gases at constant volume. Part I. Air, carbon dioxide, and hydrogen

1891 ◽  
Vol 48 (292-295) ◽  
pp. 440-441 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Specific Heat ◽  
Mean Value ◽  
Constant Volume ◽  
Specific Heats ◽  
Absolute Density ◽  
The Mean ◽  
The Absolute

In this first notice the specific heats, at constant volumes, of air, carbon dioxide, and hydrogen are treated over pressures ranging from 7 to 25 atmospheres. The range of temperature is not sensibly varied. It is found that the specific heats of these gases are not constant, but are variable with the density. In the case of air the departure from constancy is small and positive; that is, the specific heat increases with increase of the density. The experiments afford directly the mean value 0·1721 for the specific heat of air at the absolute density of 0·0205, corresponding to the pressure of 19·51 atmospheres. A formula based on the variation of the specific heat with density observed in the experiments ascribes the value 0·1715 for the specific heat at the pressure of one atmosphere.

Temperature-dependent Specific Heats of Dry Soil Materials

1975 ◽  
Vol 12 (2) ◽  
pp. 209-212 ◽  
Author(s):  
B. D. Kay ◽  
J. B. Goit
Keyword(s):  
Specific Heat ◽  
Functional Relation ◽  
Absolute Temperature ◽  
Temperature Dependent ◽  
Specific Heats ◽  
Proportionality Constant ◽  
Single Temperature ◽  
Different Temperatures ◽  
Dry Soil ◽  
The Absolute

Specific heat measurements have been made on several soil materials at different temperatures in order to obtain a generalized functional relation between specific heat and temperature. Specific heats were found to vary linearly with temperature from 200 to 300 °K (−73 °C to + 27 °C) and extrapolated close to zero at 0 °K. Consequently, the functional relation between specific heat and temperature for soil materials may be approximated as Cp = mT where Cp is the specific heat, T is the absolute temperature (°K), and m is a proportionality constant. Such a relation permits the prediction of the specific heats at any temperature normally encountered in the field once reliable specific heats have been determined at a single temperature.

The Thermoelastic Properties of Rubber

1947 ◽  
Vol 20 (2) ◽  
pp. 416-426
Author(s):  
Kurt H. Meyer ◽  
A. J. A. Van der Wyk
Keyword(s):  
Elastic Stress ◽  
Ideal Gas ◽  
Absolute Temperature ◽  
Constant Volume ◽  
Thermoelastic Properties ◽  
Ideal Behavior ◽  
Rubber Sample ◽  
The Absolute ◽  
Small Deformations

Abstract In an earlier communication, Meyer, von Susich and Valkó showed that within certain limits of extension (100 to 300 per cent) and at constant elongation, the stress in a rubber sample is proportional to the absolute temperature. Within these limits, the stress is therefore analogous to the pressure of an ideal gas, which at constant volume is likewise proportional to the absolute temperature. Such behavior of rubber or of any other rubberlike substances is said to be ideal. However, a sample of rubber which exhibits ideal behavior at elongations of 100 per cent and higher deviates from this ideal behavior at elongations below 100 per cent and greater than 500 per cent. One of the reasons for such deviations at high elongations has already been discussed in an earlier publication. As a result of extension, rubber tends to crystallize. The resulting crystallites do not contribute to the elastic stress, but if the temperature is raised, they fuse and thereby increase the tension, which then increases more rapidly than is the case with an ideal rubber. Deviations from ideal behavior at small deformations have not yet been studied thoroughly, so it is these deviations which are the first subject of discussion in the present paper. First of all the experimental facts will be presented.

scholarly journals On the measurement of the ratio of the specific heats using small volumes of gas.—The ratios of the specific heat of air and of hydrogen at atmospheric pressure and a temperatures between 20°C. and —183°C

1925 ◽  
Vol 107 (743) ◽  
pp. 510-543 ◽  
Keyword(s):  
Systematic Error ◽  
Low Temperatures ◽  
Room Temperature ◽  
Expansion Chamber ◽  
Small Vessels ◽  
Specific Heats ◽  
Large Expansion ◽  
Before And After ◽  
The One ◽  
Chamber Capacity

Introduction .—In nearly all the previous determinations of the ratio of the specific heats of gases, from measurements of the pressures and temperature before and after an adiabatic expansion, large expansion chambers of fror 50 to 130 litres capacity have been used. Professor Callendar first suggests the use of smaller vessels, and in 1914, Mercer (‘Proc. Phys. Soc.,’ vol. 26 p. 155) made some measurements with several gases, but at room temperature only, using volumes of about 300 and 2000 c. c. respectively. He obtained values which indicated that small vessels could be used, and that, with proper corrections, a considerable degree of accuracy might be obtained. The one other experimenter who has used a small expansion chamber, capacity about 1 litre, is M. C. Shields (‘Phys. Rev.,’ 1917), who measured this ratio for air and for hydrogen at room temperature, about 18° C., and its value for hydroger at — 190° C. The chief advantage gained by the use of large expansion chambers is that no correction, or at the most, a very small one, has to be made for any systematic error due to the size of the containing vessels, but it is clear that, in the determinations of the ratio of the specific heats of gases at low temperatures, the use of small vessels becomes a practical necessity in order that uniform and steady temperature conditions may be obtained. Owing, however, to the presence of a systematic error depending upon the dimensions of the expansion chamber, the magnitude of which had not been definitely settled by experiment, the following work was undertaken with the object of investigating the method more fully, especially with regard to it? applicability to the determination of this ratio at low temperatures.

Carbon Capture Performance of Amino-Modified MIL-101 at Room Temperature

2013 ◽  
Vol 395-396 ◽  
pp. 637-640
Author(s):  
Yi Yang ◽  
Zheng Ping Wang ◽  
Ling Meng ◽  
Lian Jun Wang
Keyword(s):  
Carbon Dioxide ◽  
Specific Surface ◽  
Pore Structure ◽  
Carbon Capture ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Metal Organic Framework ◽  
Adsorption Properties ◽  
Carbon Dioxide Adsorption ◽  
Before And After

MIL-101, a metal-organic framework material, was synthesized by the high-temperature hydrothermal method. Triethylenetetramine (TETA) modification enabled the effective grafting of an amino group onto the surface of the materials and their pore structure. The crystal structure, micromorphology, specific surface area, and pore structure of the samples before and after modification were analyzed with an X-ray diffractometer, scanning electron microscope, specific surface and aperture tester, and infrared spectrometer. The carbon dioxide adsorption properties of the samples were determined by a thermal analyzer before and after TETA modification. Results show that moderate amino modification can effectively improve the microporous structure of MIL-101 and its carbon dioxide adsorption properties. After modification, the capacity of MIL-101 to adsorb carbon dioxide decreased only by 0.61 wt%, and a high adsorption capacity of 9.45 wt% was maintained after six cycles of adsorption testing at room temperature and ambient pressure.

Surface pressures on a wing moving with supersonic speed

1974 ◽  
Vol 341 (1625) ◽  
pp. 177-193 ◽  
Keyword(s):  
Supersonic Flow ◽  
Delta Wing ◽  
Leading Edge ◽  
Ideal Gas ◽  
Numerical Results ◽  
Coordinate Surface ◽  
Supersonic Speed ◽  
Extrapolation Procedure ◽  
Specific Heats ◽  
Limiting Values

Estimates for pressures on the surface of a given delta wing at zero incidence in a steady uniform stream of air are obtained by numerically integrating two semi-characteristic forms of equations which govern the inviscid supersonic flow of an ideal gas with constant specific heats. In one form of the equations coordinate surfaces are fixed in space so that the surface of the wing, which has round sonic leading edges, is a coordinate surface. In the other, two families of coordinates are chosen to be stream-surfaces. For each form of the equations, a finite difference method has been used to compute the supersonic flow around the wing. Convergence of the numerical results, as the mesh is refined, is slow near the leading edge of the wing and an extrapolation procedure is used to predict limiting values for the pressures on the surface of the wing at two stations where theoretical and experimental results have been given earlier by another worker. At one station differences between the results given here and the results given earlier are significant. The two methods used here produce consistent values for the pressures on the surface of the wing and, on the basis of this numerical evidence together with other cited numerical results, it is concluded that the pressures given here are close to the true theoretical values.

Split face comparative study of microneedling with platelet rich plasma versus Fractional carbon dioxide laser with platelet rich plasma in treatment of atrophic post acne scars

QJM ◽  
2021 ◽  
Vol 114 (Supplement_1) ◽  
Author(s):  
Mohamed Abd Elnaeem Sallam ◽  
Khaled El Zawahry ◽  
Abdul Rahman Muhammed Ali Mustafa
Keyword(s):  
Carbon Dioxide ◽  
Co2 Laser ◽  
Carbon Dioxide Laser ◽  
Platelet Rich Plasma ◽  
Fractional Co2 Laser ◽  
Acne Scars ◽  
Significant Difference ◽  
Before And After ◽  
The Face ◽  
Fractional Carbon Dioxide Laser

Abstract Background Acne scars, is a challenge for dermatologists, despite having multiple treatment modalities like microneedling, dermabrasion, Fractional CO2 Laser, dermal fillers, etc. However, monotherapy has been hardly satisfactory because of the polymorphism seen with the scars. Objective Comparison between microneedling with platelet rich plasma versus Fractional carbon dioxide laser with platelet rich plasma in treatment of atrophic post acne scars. Patients and methods This study was carried out in department of dermatology, venereology and andrology, in Kobry El-Kobba Military complex during the period (from September 2018 to July 2020 ) on 20 patients of both sexes aged from 20 to 60 years old presenting with Goodman and Baron Grade II, III, IV acne scars . Results The study revealed a statistically significant difference (p = 0.017) between Goodman and Baron scar grades on the right side of the face before and after treatment indicating that microneedling with platelet rich plasma was effective in improving acne scars. Also, there is a statistically significant difference (p = 0.010) between Goodman and Baron scar grades on the left side of the face before and after treatment, indicating that fractional CO2 laser with platelet rich plasma was effective in improving acne scars. Conclusion and recommendation Further controlled and randomized studies are needed to validate our findings in a larger cohort of patients and longer follow up. Also, number of sessions might be more than 3 sessions.

Breathing in brief exercise

1960 ◽  
Vol 15 (4) ◽  
pp. 583-588 ◽  
Author(s):  
F. N. Craig ◽  
E. G. Cummings
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Respiratory Exchange Ratio ◽  
Metabolic Cost ◽  
Carbon Dioxide Tension ◽  
Minute Volume ◽  
Carbon Dioxide Output ◽  
Respiratory Minute Volume ◽  
Before And After

Two men ran for 20 or 60 seconds while inhaling air, oxygen or 4% carbon dioxide. Inspired respiratory minute volume was determined for each breath. Ventilation increased suddenly in the first breath with minimal changes in end-expiratory carbon dioxide tension and respiratory exchange ratio to a rate that remained constant for 20 seconds before increasing further. The rate of carbon dioxide output was uniform during the first 20 seconds. A 12% grade did not increase ventilation or oxygen uptake during runs of 20 seconds, but in the first minute of recovery, ventilation was 64% greater than after level runs. Inhalation of oxygen inhibited ventilation by 24% in the 20-second periods before and after the end of a 60-second run. Inhalation of carbon dioxide begun at rest produced increments in ventilation and end-expiratory carbon dioxide tension that varied little during running and recovery. In the 20-second runs ventilation varied with speed but appeared independent of ultimate metabolic cost. Submitted on January 21, 1960

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