Silver specific heat

Systems may be in chemical or mechanical equilibrium, and they may also exhibit thermal equilibrium. If a hot object is placed in contact with a colder mass of the same material inside an insulated container, heat flows from the hot object into the colder object until the temperatures of the two are equal. Heat lost by the warm object is equal to the amount gained by the cold object. The amount of heat needed to raise the temperature of an object a certain amount is equal to the amount which that object would lose in cooling by the same amount. The amount of heat needed to warm or the amount lost when cooling equals the product of the specific heat (or heat capacity) of the substance, the mass, and the change in temperature. For example, if a 50-gram (1.8-ounce) piece of silver at 70°C (158°F) is placed in 50 grams (1.8 ounces) of water at 15°C (59°F), the principle of thermal equilibrium can be used to calculate the final temperature of the water and silver ... 

When determined from the physical constants, the values of the time constant are found to vary because of the appreciable change of the specific heat with temperature. The precision is limited by the uncertainties in the values of the thermal conductivity of powders. Large single diamond crystals have a high thermal conductivity (see Table I), being of the same order of magnitude as for silver... 

Iridium is a hard, brittle metal, which can be filed and which takes a polish. In appearance it lies between silver and tin it is not ductile, however, even at red Mat. Its specific heat is 0-0323,3 and its coefficient of linear expansion with rise of temperature (0-80° C.) is 0-000,007.4 The density of the native metal is 22-6 to 22-8.5 For the pure cast metal the value 22-42 has been found.6 It melts at 2290° C.7 and distils in the electric furnace, its boiling-point being approximately 2550° C. Its vapour, on cooling, is deposited as small crystals.8 Liquid iridium dissolves carbon, but liberates it, on cooling, in the form of graphite.9... 

Other properties of aqueous solutions investigated are density,3 refractive index,4 molecular elevation of the boiling-point,6 vapour-pressure,6 specific heat,7 and electric conductivity.8 References are also appended to work on the compressibility,9 the solubility in organic solvents10 and sulphurous acid,11 the molecular weight in liquid sulphur dioxide,11 the electric conductivity in acetone12 and dilute alcohol,13 the non-existence of polyiodides,14 isomorphism with potassium iodide,15 and the formation of a double salt with silver iodide.16... 

An example will make this law more intelligible. The specific heat of silver is. 057 if 6.4 is divided by this num-... 

Latent heats of evaporation of liquefied gases at low temperatures have been determined by various methods. Dewar, and Behn, dropped pieces of metal of known specific heat into the liquid and measured the gas evolved. Estreicher heated the liquid in a double Dewar vessel electrically and measured the volume of gas evolved. In Donath s apparatus (Fig. 4.VIII L) the gas passed through a copper spiral in a block of lead A, so assuming a constant temperature about 2° above the temperature in the metal calorimeter B. The gas then passed to a vessel inside B connected by a thin German-silver tube. The calorimeter was in two parts, between which was a platinum heating spiral for determining the thermal capacity. Outside was an adiabatic mantle C. The whole was in a vacuous copper jacket D. The temperature differences between A and B, and B and C, were determined by thermocouples. The rise in temperature... 

Calculating from this table, we find the true specific heat of silver at 100° to be 0 0566. The mean specific heat between... 

Use the empirical rule of Dulong and Petit stated in Problem 7 to estimate the specific heat capacities of vanadium, gallium, and silver. 

Q.9.10 After reaching 327.5°C, a large section of the metal chunk melts, demonstrating tliat the metal chunk is a mixture of at least two different metals. A 0.8 kg dull silver chunk has a specific heat capacity of 0.13 kJ/kg-K. Can the specific heat capacity of the remaining chunk be determined without directly measuring it If yes, calculate it. 

As an example, let us deal with silver, which is conveniently obtainable in an extremely pure state, and for which particularly reliable measurements are consequently available. In order to derive the atomic weight, the measured specific heat must be reduced to constant volume, and then that factor must be found which, multiplied by the specific heat, best reproduces the variation required by equation (18) this factor is then equal to the atomic weight. 

From the practical point of view, we must not give undue weight to this good agreement, which is probably to be ascribed to the fact that exact results have been obtained for the specific heat of silver by different observers but it may well serve to indicate afresh that the theoretical foundations for the law of Dulong and Petit are now just as well established as those for the law of Avogadro have been for many years. 

Affinity between Silver and Iodine.—When I compared the heat evolution and affinity in this case, greater differences appeared at first than were to be expected, on our Theorem, from the variation of the specific heats. I therefore set Herr Ulrich Fischer (74) the detailed examination of the case he showed conclusively that Thomsen s value for the heat of formation (13,800 cals.) was very considerably in error. From the temperature coefficient of the E.M.F. of the silver-iodine electrode, Fischer found 15,170 and, by... 

If p, the vapour pressure of solid iodine, is known at any given temperature, we can hence calculate it, the dissociation tension of silver iodide at this temperature. We know the equilibrium between solid silver, silver iodide, and gaseous iodine for all temperatures if the vapour-pressure curve of iodine is given according to classical thermodynamics this is the case if, in addition to the specific heat of solid iodine already required for the calculation of A, we know that of iodine vapour as well, and also either the heat of evaporation and the vapour pressure at one temperature, or the vapour pressures at two temperatures. 

We have already (p. 115) had an example of such an application the values found by U. Fischer for the heat of formation of silver iodide by means of formulae (99) and (100) should be more reliable than that obtained by equation (1). For though the electro-motive force of the cell in question could be determined at one temperature with sufficient accuracy (about 1 per 1000), the temperature coefficient could not be obtained so precisely as to allow the determination of U also to 1 per 1000 by equation (1) for the use of formula (100), on the other hand, the specific heats need be known with only moderate accuracy, since they serve only to determine the relatively small difference A — U. The case is similar in the following example. 

Reference may also be made here to the new measurements of specific heat by means of the vacuum calorimeter, to which we have already alluded on page 233. The authors mentioned made use of an apparatus which was essentially the same as that described by Schwers and myself the temperature was measured by means of a platinum wire, through which passed an extremely constant current, so that the resistance could be measured by the potential drop, using a potentiometer. During the heating a silver voltameter was included in the circuit as a control on the measurement of time convenient though this is, I think that as a rule the determination of the duration of the heating current can be made with sufficient accuracy to allow the somewhat troublesome silver estimation to be avoided. 

Table 10.1 shows that silver has a specific heat capacity of 0.24 J/g °C. The metal is silver. 

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