Coefficient Of Cubical Expansion Research Articles

Some Properties of van der Waals' Liquids

A theoretical consideration of the volume of a van der Waals' liquid suggests some new rules, comparable to that of Trouton, relating coefficients of expansion and compressibility to heats of vaporization. According to the simplest and most reliable of these new relationships, the product of the coefficient of cubical expansion and the heat of vaporization, αΔHv, is the same for many liquids and equal to about 10 cal./deg. It is further shown that at a given temperature, ΔHv2β/V is also constant where β is the compressibility and V the volume of the liquid. Certain corollary rules are derived by combining the above two with each other and with Trouton's law. These new rules should prove of some value in estimating compressibilities and heats of vaporization from coefficients of expansion.

Convection Currents in Porous Media: II. Observation of Conditions at Onset of Convection

Small-scale experiments have been carried out for determining the minimum vertical thermal gradient which is required to cause convection in liquids entrapped in porous media. Observations relative to the onset of convective flow in unconsolidated sands indicate that the present theories predict minimum gradients which are excessive by considerable amounts, possibly because they neglect the temperature-dependence of viscosity. The ratio of theoretical to observed gradients is found to be roughly R=(Kh2μAV/kρα)0.51,where h2 is the thermal diffusivity, μAv is average viscosity, k is flow-permeability, ρ is density of liquid, α is the coefficient of cubical expansion of the liquid, and where K = 10−3 sec.2 per cm2 °C for c.g.s. units. By extrapolation, it is possible to strengthen the earlier conclusion that convection occurs in the Woodbine sand near the Mexia fault zone.

Effect of temperature on the volume of leather and collagen in water

The coefficients of cubical expansion of 10 tannages of leather and tendon collagen have been measured by using water as the confining liquid. The results, calculated for dry leather of density 1.560 g/ml, show that an average coefficient of 540X10~/°C applies for collagen and all leathers except chrome-vegetable leather, the coefficient of this tannage being 340X 10~/°C. These averages have a reproducibility indicated by standard deviations of 13X10-/°C and 37X10-/°C, respectively. The or transition temperature is a band rather than a sharp point on the temperature scale. During apparent shrinkage, an increase in real volume of approximately 1 percent occurs. This increase in volume is irreversible, but the thermal expansion below the transition range is nearly completely reversible. The rate of expansion during transition of collagen follows the law of a firstorder reaction. The results are interpreted as indicating that the shrinkage does not occur at a characteristic temperature but is a rate process. The transition may be pictured as a change of state possibly coupled with a reaction.

Convection Currents in a Porous Medium

The problem is considered of the convection of a fluid through a permeable medium as the result of a vertical temperature-gradient, the medium being in the shape of a flat layer bounded above and below by perfectly conducting media. It appears that the minimum temperature-gradient for which convection can occur is approximately 4π2h2μ/kgρ0α D2, where h2 is the thermal diffusivity, g is the acceleration of gravity, μ is the viscosity, k is the permeability, α is the coefficient of cubical expansion, ρ0 is the density at zero temperature, and D is the thickness of the layer; this exceeds the limiting gradient found by Rayleigh for a simple fluid by a factor of 16D2/27π2kρ0. A numerical computation of this gradient, based upon the data now available, indicates that convection currents should not occur in such a geological formation as the Woodbine sand of East Texas (west of the Mexia Fault zone); in view of the fact, however, that the distribution of NaCl in this formation seems to require the existence of convection currents, and in view of the approximations involved in applying the present theory, it seems safe tentatively, to conclude that convection currents do exist in this formation and that the expression given above predicts excessive minimum gradients when applied to such a formation.

The determination of the coefficient of cubical expansion of solid benzoic acid by means of a gas-filled dilatometer

The determination of the coefficient of cubical expansion of solid benzoic acid by means of a gas-filled dilatometer

Societies and Academies

LONDON. Physical Society, June 14.-Prof. A. Schuster, F.R.S., president, in the chair.-T. H. Blakesley: Demonstration of the use of specific gravity balls for determining very small differences of density. Experiments were quoted which indicate a sensibility such that the error which might be expected in a properly conducted experiment would be of the order 5 in the sixth decimal place. Specific gravity balls have been employed for the purpose of discriminating between the qualities of potable waters in respect of density and of testing the efficacy of softening processes. A thermometer of open scale is employed to give the temperature at which a specific gravity ball is in equilibrium with a liquid being slowly warmed or cooled through that point of temperature. If such a determination is made in distilled water at ordinary atmospheric temperatures it fixes the specific gravity of the ball at the temperature of equilibrium within four or five units in the sixth place of decimals. If a second observation with the same ball is made in a slightly heavier liquid, the temperature of equilibrium will be considerably higher, perhaps 2° or more, than in distilled water. By applying the coefficient of cubical expansion the density of the ball at the higher temperature can be obtained, and this is the density of the second specimen of water at the second temperature. Reference to a table of densities of distilled water will furnish its density at the higher temperature, and the difference between the two numbers will give what the author calls the density excess of the second liquid over distilled water at the higher of the two temperatures. This density excess is best quoted in parts in one million.-Dr. H. F. Haworth: Maximum sensibility of a Duddell vibration galvanometer. The maximum sensibility of a moving coil vibration galvanometer as a voltage detector is obtained when the flux through it is so adjusted that the back E.M.F. of the coil is equal to its CR drop; then the back E.M.F. is equal to half the applied voltage, and the current is equal to V/aR, and is in phase with the applied voltage. Increases of current sensibility of about 30 per cent, at 200 ˜ and 40 per cent, at 1000 ˜ were obtained on running the instrument in a vacuum, thus showing that a large part of the mechanical work produced was used in overcoming the molecular friction of the system.-F. Stroude: An accurate examination of the Steinmetz index for transformer iron, stalloy, and cast-iron. Experiments to provide an experimental basis, suitable for mathematical analysis, with the view of discovering some relation connecting hysteresis loss and flux density which will accord with results obtained practically to a greater extent than the empirical law due to Steinmetz. Experiments were made with transformer iron stalloy (3 per cent, silicon iron) and cast-iron, two rings of each material being tested. A set of comparative tests on one of the transformer iron rings was made by the ballistic method, and these tests show that, in general, for a given value of B the hysteresis loss and the value of H for the ballistic tests are higher than the corresponding values for the slow cyclic tests.

The Density and Coefficient of Cubical Expansion of Ice

There are perhaps no subjects in the domain of experimental physics which call more urgently for attention, than investigations into the properties of water in its various states of aggregation. And of the various points which still need study, the latent heat of fusion is without doubt the most pressing. The method which promises to yield a reliable result for this determination, requires a knowledge of the density of ice at 0° C. The Bunsen Ice Calorimeter has, in the hands of Dieterici and other Continental physicists, recently become an instrument of precision, but the results which this apparatus is capable in itself of yielding, are unavailable to Science owing to the lack of an accurate knowledge of the density and latent heat of ice.

The density and coefficient of cubical expansion of ice

After an account of the methods employed by previous experimenters in the subject, reference is made to the views of Nichols, according to which two distinct kinds of ice have been subjected to experiments. The density of artificial ice is about 0·916 gramme per cubic centimetre, while that of natural ice is more than one part in a thousand greater. Two tables are given showing in the first all the results which have been published concerning the density and coefficient of cubical expansion of ice, and in the second the same results tabulated separately according to the variety of ice used.

Papers read to the Society, February 6, 1902.

I. “The Stratifications of Hydrogen.” By Sir William Crookes, F. R. S. II. “Radio-activity and the Electron Theory.” By Sir William Crookes, F. R. S. III. “The Density and Coefficient of Cubical Expansion of Ice.” By Dr. J. H. Vincent. Communicated by Professor J. J. Thomson, F. R. S. IV. “On the Increase of Electrical Resistivity caused by Alloying Iron with Various Elements, and the Specific Heat of those Elements.” By Professor W. F. Barrett, F. R. S. V. “Continuous Electrical Calorimetry.” By Professor H. L. Callendar, F. R. S.

XI. The density and coefficient of cubical expansion of ice

There are perhaps no subjects in the domain of experimental physics which call more urgently for attention, than investigations into the properties of water in its various states of aggregation. And of the various points which still need study, the latent heat of fusion is without doubt the most pressing. The method which promises to yield a reliable result for this determination, requires a knowledge of the density of ice at 0° C. The Bunsen Ice Calorimeter has, in the hands of Dieterici and other Continental physicists, recently become an instrument of precision, but the results which this apparatus is capable in itself of yielding, are unavailable to Science owing to the lack of an accurate knowledge of the density and latent heat of ice.

Determination of the coefficient of cubical expansion of a solid from the observation of the temperature at which water, in a vessel made of this solid, has the same apparent volume as it has at O degrees C; and on the coefficient of cubical expansion of a substance determined by means of a hydrometer made of this substance

Determination of the coefficient of cubical expansion of a solid from the observation of the temperature at which water, in a vessel made of this solid, has the same apparent volume as it has at O degrees C; and on the coefficient of cubical expansion of a substance determined by means of a hydrometer made of this substance