Mercury calorimeter

Because the heat to be measured is usually brought to a vessel containing water, most calorimeters used in this method can be called water calorimeters . Examples James Watt (1786), Regnault (1840), Favre and Silbermann (1845), Berthelot (1875). Other liquids can be used Favre and Silbermann s mercury calorimeter. 

Favre and Silbermann used a mercury calorimeter consisting of an iron... 

In 1865 Raoult measured the chemical (q) and voltaic (w) heat for several cells, the first by the heat of reaction in a Favre and Silbermann mercury calorimeter, and the second by a sine galvanometer (giving the e.m.f.) and a tangent galvanometer (giving the current) used simultaneously, with the e.m.f. of the Daniell cell as standard and unit quantity of electricity as that combined with i gm. of hydrogen or the equivalent of another ion. The product of these was equivalent to 23 9 kcal., and the heat evolved in precipitating copper by an equivalent of zinc was 23 2 kcal., nearly the same. But in other cases there were appreciable differences ... 

The calorimetric thermometer measures temperature changes within the calorimeter bucket. It must be able to provide excellent resolution and repeatability. High single-point accuracy is not required since it is the change in temperature that is important in fuel calorimetry. Mercurial thermometers, platinum resistance thermometers, quartz oscillators, and thermistor systems have all been successfully used as calorimelric thermometers. 

The Beckmann thermometer used with the bomb calorimeter should be calibrated for the normal depth of immersion with which it is used. To cover the normal range of laboratory temperatures, this calibration should be obtained for three settings of the zero on the scale, convenient values being 10, 15, and 20°C. Such a series of calibrations allows automatically for emergent stem corrections and variations in the value of the degree on the thermometer scale with different quantities of mercury in the bulb, in addition to those arising from inherent variations in the diameter of the capillary bore. 

One source of error in this method (ASTM D-3286) is in temperature measurement. If a mercury-in-glass thermometer is used, it must be calibrated accurately and consistent readings must be made. Many calorimeters are equipped with digital thermometers with thermistor probes and microprocessors to control the firing and record the temperatures at prescribed intervals. This alleviates most of the human error in recording the temperature changes. 

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. 

Experimental. A Parr model 1221 oxygen bomb calorimeter was modified for isothermal operation and to ensure solution of nitrogen oxides (2). The space between the water jacket and the case was filled with vermiculite (exploded mica) to improve insulation. A flexible 1000-watt heater (Cenco No. 16565-3) was bent in the form of a circle to fit just within the jacket about 1 cm. above the bottom. Heater ends were soldered through the orifices left by removing the hot and cold water valves. A copper-constantan thermocouple and a precision platinum resistance thermometer (Minco model S37-2) were calibrated by comparison with a National Bureau of Standards-calibrated Leeds and Northrup model 8164 platinum resistance thermometer. The thermometer was used to sense the temperature within the calorimeter bucket the thermocouple sensed the jacket temperature. A mercury-in-glass thermoregulator (Philadelphia Scientific Glass model CE-712) was used to control the jacket temperature. 

Bomb calorimeter (Parr design), shown with an adiabatic jacket, which may also be used empty as an insulating air jacket. The precision mercury thermometer can be replaced by a high-resolution resistance thermometer or a calibrated thermistor. 

Method. The calorimeter is generally kept well insulated so that loss or gain of heat from the environment is minimum. A sensitive thermometer estimates the temperature changes inside the calorimeter. A mercury Beckmarm Thermometer was used extensively in the past but now many reliable and more accurate devices are available such as resistance thermometers and also semi-conducting devices like thermistors. 

A tube of mercury formed the inner tube of a Bunsen s ice calorimeter (Fig. l.VIII F see 8.IX M), and was in the centre of a larger tube containing mercury, heated above by a current of steam. The temperature of the central tube, of cross-section A, was uniform, and if / is the distance between two sections with temperatures ti and tz (ti>t2X and q the measured quantity of heat flowing into the calorimeter per sec. ... 

Direct measurements were made by Lussana, who drove the heated liquid under pressure by a pump into a calorimeter, or heated electrically the liquid under pressure. He found the effect of pressure small, and observed both increase and decrease of specific heat with increase of pressure (values for mercury calculated by Bridgman are included in the last three columns) ... 

Very rapid and efficient stirring of the water in the calorimeter was necessary and a correction for the heat produced by this (in some cases 10 per cent of the whole energy supplied) was necessary. Temperatures were read on a mercury thermometer compared with a standard mercury thermometer and a platinum thermometer. Griffiths, who took the e.m.f. of the Clark cell as 1 4342 volt, found, in 15° g.cal. and nitrogen thermometer temperatures, 4=572 60 at 40 15° and 578 70 at 30 00°, and by combining his results with those of Dieterici at 0° and of Regnault between 63° and 100° he concluded that ... 

The solid used in Bunsen s calorimeter is pure ice, which is kept at 0° C. by immersing the calorimeter (Fig. 7) in a mixture of crushed ice and water. The tube C is filled with mercury, while B contains water, part of which has been converted into ice by cooling the inside of the tube A with a freezing mixture. The heat evolution which we wish to investigate is then made to take place in A. 

Two cast-iron wheels were made to rotate and rub against one another under mercury, which served as the calorimeter... 

For very accurate determinations E. Fischer and Wrede substitute a platinum resistance thermometer for the mercury thermometer, and emphasise the importance of efficient stirring of the water in the calorimeter. In this way they determined with the greatest care the heats of formation of cane sugar (3954 cal. per gram) and benzoic acid (6328 cal. per gram), and recommend these substances for the cahbration of calorimeters. 

The output of primers includes hot gases, particles, a pressure pulse, and sometimes a shock wave. Parameters which have been measured to characterize the primer include the volume of gas emitted, the impulse imparted to a column of mercury, the light output, the temperature rise of a calorimeter, the pressure, the conductivity between probes, and the functioning time. No general quantitative relationship between the parameters and the initiation of the next explosive in the element or train has yet emerged, although individually they may all have some importance [2,5.6]. 

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