The copper calorimeter

The Copper Calorimeter.—The first description of this apparatus was given by W. Nemst, F. Koref, and F. A. Lin-demann (36) detailed instructions for its use were given later by Koref (60), who has carried out a large number of valuable measurements with it. The work was then continued by A. S. Russell (79a) and Ewald (99) the latter, in the examination of ammonium compounds, discovered the remarkable fact that there is here a transient decrease of specific heat with rise of temperature over a certain range, which points to internal rearrangements in the ammonium radicle. 

The calorimeters devised by Schottky (22) and Schlesinger (20) may be mentioned as forerunners of the copper calorimeter in certain respects. 

The copper calorimeter works on the principle of the mixture calorimeter in place of the calorimetric liquid there is a copper block with good thermal insulation, provided with an axial cavity for receiving the warmer or cooler substance under investigation. The change in the temperature of the block is measured with the aid of thermocouples the good thermal conductivity of copper ensures that all parts of it are always at practically the same temperature. With a view to the best thermal in-FlG 3- sulation, it is contained in a double-walled vessel which is evacuated and silvered. 

The arrangement of the complete apparatus is shown in Fig. 3. K is the copper block weighing some 400 gms., which is set in the vacuum vessel D TT are the thermocouples. The lower junctions are contained in small thin-walled glass tubes inserted into the copper block to pro- 

The whole apparatus is immersed up to n in a bath of constant temperature ice or carbon dioxide snow is usually employed for the purpose. The temperature of the upper copper block is thus maintained constant. Since there are difficulties in making the joints tight, the whole of the apparatus is encased watertight by a sheath of thin copper foil suitably soldered this is shown dotted in the figure. 

---

Page 14, line 2 The method of Nernst, Koref, and Lindemann, by the use of the copper-calorimeter, determines the mean specific heat over a range of temperature. The mode of procedure is the same as in ordinary calorimetry, except that a hollow block of copper, the temperature of which is determined by means of inserted thermoelements, is used instead of a calorimetric liquid, and the method therefore made applicable to very low temperatures. 

In conjunction with my fellow-workers, I constructed two types of calorimeter, the copper calorimeter and the vacuum calorimeter since the latter apparatus is of particular importance for our purpose, it will be described in more detail in its different forms. 

As A. Magnus has shown ( Physik. Zeitschr.," 1913, p. 5), the copper calorimeter may also be used for the determination of specific heats at high temperatures, if a large block of copper is employed. 

As a further control, the copper calorimeter of Fig. 9 was replaced by the lead block accurately examined by Eucken and Schwers (p. 37). The above table was corrected with the aid of these numbers this could easily be done as the... 

To this end I searched for methods which should be very different, and therefore mutually confirmatory I think I have found them in the above described copper calorimeter and vacuum calorimeter. The latter apparatus is, of course, much more suited to our problem, since it gives the true specific heats (or, rather, the mean specific heats for a very small interval of temperature) but the copper calorimeter has also rendered us valuable service in completing, and above all in controlling, the results. For wherever a mutual control was possible—and the number of such examples is very large—an extremely satisfactory concordance has been shown between the values obtained this, of course, says much for the reliability of both methods. 

It is known from the investigations of Tammann that benzophenone and betol are capable of extensive supercooling but difficulties, which have not yet been fully explained (Koref, 60), have been encountered in making accurate determinations, for the values obtained for the specific heats show unusually large variations. Examination of the supercooled substances was not possible in the vacuum calorimeter with the copper calorimeter the following numbers were obtained (60) —... 

Exactly three grams of carbon were burned to CO2 in a copper calorimeter. The mass of the calorimeter is 1500 g and the mass of the water in the calorimeter is 2000 g. The initial temperature was 20.0°C and the temperature rose to 31.3°C. Calculate the heat of combustion of carbon in joules per gram. The specific heat of copper is 0.389 J/g K. 

The type of calorimeter and the method of calculating the heats of adsorption from the experimental data were essentially the same as described in previous papers (I, 4, 10). Two calorimeters of the same design were used, one employing a filler made of copper as described by Dry and Beebe (4) and the other a filler of aluminum. (A drawing and brief description of this calorimeter will be supplied on request addressed to the authors at Amherst College.) In one run for nitrogen adsorption on the bare surface we employed a liquid nitrogen trap to prevent contamination of the sample in the calorimeter by condensed mercury. Data from all runs on the various calorimeters and samples checked within the accuracy of the experiments. 

A 46.2-g sample of copper is heated to 95.4°C and then placed in a calorimeter containing 75.0 g of water at 19.6°C. The final temperature of the metal and water is 21.8°C. Calculate the specific heat capacity of copper, assuming that all the heat lost by the copper is gained by the water. 

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... 

For the drop technique, the isoperibolic calorimeters are most frequently used. The calorimetric device consists of two main parts a furnace and a heated block. Between the calorimetric block and the furnace, there is a system of shields controlled by a mechanic, hydraulic or electromagnetic device, which prevents the heat transfer from the furnace to the calorimetric block. The calorimeter is made of copper with a cavity closed by a shield. A resistance thermometer wound on the block measures its temperature. Such a calorimeter can work up to 1700°C, especially when the furnace... 

The authors reacted Na2Se03(cr) with a copper sulphate solution in an electrically calibrated calorimeter and measured the enthalpy change of the reaction. The product was CuSe03-2H20(cr) as shown by chemical analysis and X-ray diffraction. Crystalline anhydrous copper selenite was also prepared and the integral enthalpies of dissolution of the two selenites in 8% HMO3 (HNO3, aq 1 40, and denoted sin below) were determined. The data have been used in Table A-45 to calculate standard enthalpies of formation of the copper selenites. 

Figure 15. Bismuth-Telluride Thermopile, 21, mounted in a heat conduction calorimeter. 13, the leads 18, the heater 20, the copper cell holder 19, the cell and 22, the entrance channel.

As regards the arrangements for bringing the substance to be introduced into the copper block to a known higher or lower temperature, the above-cited work of Koref, and the other literature mentioned, may be consulted. Once the apparatus is properly set up, results may be obtained with it rapidly and very accurately. It should be useful, and in most cases preferable to the ice calorimeter, not only for the determination of heat capacities, but whenever the calorimetric determination of small quantities is required. ... 

The arrangement of the calorimeter itself is illustrated in Fig. 9. The lead block, shown shaded, is seen above with the copper sheath fitting on to it. The sheath is wound about its middle with thin lead wire, from eacii end of which two connections are taken, so that the temperature of the sheath may be measured. The lead wire was insulated by... 

The ARC calorimeter jacket and sample system are shown in Figure 11.49 (168). A spherical bomb is mounted inside a nickel-plated copper jacket with a swagelok fitting to a 0.0625 in. tee, on which is attached a pressure transducer and a sample thermocouple. The jacket is composed of three zones, top, side, and base, which are individually heated and controlled by the Nisil/Nicrosil type N thermocouples. The thermocouples are cemented on the inside surface of the jacket at a point one quarter the distance between the two cartridge heaters. The point is halfway between the hottesl and coldest spots of the jacket. The same type of thermocouple is clamped directly on the outside surface of the spherical sample bomb. All the thermocouples are referenced to the ice point that is designed to be stable to within 0.01°C. Adiabatic conditions are achieved by maintaining the bomb and jacket temperatures exactly equal. The sample holder has a capacity of 1-10 g of sample. Pressure in the system is monitored with a Serotec 0-2500 psi TJE pressure transducer pressure is limited in the vessel to 2500 psi. The maximum temperature of the system is 500°C. 

In the flame impingemenf study by Baukal [17], a Type K thermocouple was imbedded in the impingement rings of copper calorimeters (see Figure 5.14). The... 

EN 367 [69] specifies a method for comparing heat transmission through materials used in protective clothing see Fig. 15. The horizontal specimen is exposed to an incident heat flux of 80 kW/m" generated by a calibrated Meker propane burner beneath the specimen. A copper calorimeter is positioned on the upper surface of the specimen, and the time in seconds is determined for the temperature of the calorimeter to rise by 24 C. 

Styrofoam cups and the heat necessary to raise the temperature of the inner wall of the apparatus. The heat capacity of the calorimeter is the amount of heat necessary to raise the temperature of the apparatus (the cups and the stopper) by 1 K. Calculate the heat capacity of the calorimeter in J/K. (d) What would be the final temperature of the system if all the heat lost by the copper block were absorbed by the water in the calorimeter ... 

A specimen of 100 mm square is fastened horizontally and then ignited from below by a Maker burner with a flame burning a controlled amount of gas metered through a rotameter. Temperature rise is measured above the ignited point at the surface of the specimen by a copper calorimeter with 3 sensors. The thermal protective performance rating is calculated from the amount of energy transmitted per unit area (F) determined by preliminary calibration and from the exposure time (time to the thermal end-point, t) ... 

A unique solution to fast DTA is the foil calorimeter, shown schematically in Fig. A. 10.4. A copper-foil is folded in such a way that two sheets of the sample (also very thin, so that the mass remains small) can be placed between them. The copper foil is used as the carrier of electrical current for fast heating. Between the inner portion of the stack of copper foil and sample, a thin copper-constantan thermocouple is placed. Only three folds of the stack are shown. In reality, many more folds make up the stack so that there are no heat losses from the interior and measurements can be made under adiabatic conditions. Heating rates of up to 30,000 K min" (500 K s" ) have been accomplished. Measured is temperature, time, andthe-rate-of-change of temperature for a given heat input. With such fast heating rates it becomes possible to study unstable compounds by measuring faster than the decomposition kinetics of the compound. This super-fast calorimeter has seen httle apphcation, likely because it requires a new calorimeter for each sample. 

A coffee-cup calorimeter of the type shown in Figure 5.17 contains 150.0 g of water at 25.1 °C. A 121.0-g block of copper metal is heated to 100.4 °C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g-K. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.1 °C. (a) Determine the amount of heat, in J, lost by the copper block, (b) Determine the amount of heat gained by the water. The specific heat of water is 4.18 J/g-K. (c) The difference between your answers for (a) and (b) is due to heat loss through the Styrofoam cups and the heat necessary to raise the temperature of the inner wall of the apparatus. The heat capacity of the calorimeter is the amount of heat necessary to raise the temperature of the apparatus (the cups and the... 

---