Theories Thermometers

The theory of the process is discussed in Sections 1,1-1,3. The apparatus of Fig. 11,12,1 may be used when moderate quantities of the substance are available. A is a 50 ml. distilling flask attached by a cork to a Liebig condenser B, upon the end of which an adapter C is fitted D is a receiver for collecting the distillate. The thermometer E is fitted into the neck of the distilling flask by means of a well-bored cork the bulb of the thermometer should be in the centre of the neck of the flask and slightly below (ca. 5 mm.) the level of the side tube. The flask may be heated on a wire gauze with asbestos centre or preferably in an air bath (Fig. 77, 5, 3). 

Thermochemistry, 254, 507 Thermodynamic potentials, 99 Thermo-electric circuit, 450 inversion, 451 theories, 453 Thermometers, 3, 140, 166 Thermometry, 1, 353 Thomsen-Berthelot principle, 257, 506... 

Five to ten grams of tris (ethylenediamine) chromium (III) chloride SU-hydrate are spread in a thin even layer on an open Petri dish embedded in a sand bath that carries a thermometer. The bath is maintained at 210°C until the product lias lost at least 25% of its original weight (theory = 80.6%). The evolution of amine soon begins and the yellow salt slowly darkens over a period of an hour or two, finally yielding a red-violet material. 

A solution of 91 g. (1 mol) of thiosemicarbazide4 in 350 ml. of 3 N HC1 (1 mol) is prepared. A clear solution is obtained at 30°. The solution is placed in a 1-1., threenecked flask equipped with a mechanical stirrer, thermometer, and dropping funnel and cooled in an ice-salt bath to 10°. A portion of the dissolved thiosemicarbazide precipitates at this stage. A solution of sodium nitrite, 69 g. (1 mol) in 150 ml. of water, is placed in the dropping funnel. The total volume of the solution is 180 ml. The sodium nitrite solution is added dropwise to the stirred mixture, while the temperature is maintained at 10°. When about 130 ml. of the solution has been added (45 minutes), the addition is stopped and the fine white crystalline precipitate filtered off. The filtrate, which is pale blue in color, is put back into the reaction flask and the addition of the sodium nitrite solution continued. The temperature of the reaction mixture should be maintained at 10 to 15° throughout the addition of the sodium nitrite. When about 40 ml. more of the sodium nitrite solution has been added (15 minutes), the reaction mixture tends to assume a very pale yellow color. Addition of the sodium nitrite is stopped at this stage and the rest of the precipitate filtered off. The addition of even a few drops of the sodium nitrite solution to the filtrate causes an intense yellow color. The filtrate is discarded at this stage. The combined precipitates of 5-amino-l,2,3,4-thiatriazole is washed three times with small amounts of ice-cold distilled water and dried under vacuum over sulfuric acid. The yield is 81.5 g. or 80% of theory, f... 

The third section of the memoir, Reflections on the theory of heat, summarized lucidly what Lavoisier and Laplace sought to accomplish with their machine exact quantitative control of the distribution and the flow of heat in a system of bodies. In order to frame a complete theory of heat, four different kinds of measurement were necessary a linear thermometer, the specific heats of bodies as a function of temperature, the absolute quantities of heat contained in bodies at a given temperature, and the quantities of heat evolved or absorbed in chemical combinations or decompositions. This is in fact an excellent summary of the directions in which the thermometric investigation of heat had proceeded until then, except for the last item, which Lavoisier and Laplace added. They could not measure all these quantities directly, however, as they readily admitted. Particularly problematic was the relationship between the thermometer readings and the absolute quantities of heat. The assumption that the ratio of absolute heats was proportional to the ratio of specific heats was very uncertain and would require many experiments for confirmation. Specific heats only indicated the difference... 

Place in the flask 12 g of red phosphorus and 300 g of glacial acetic acid. Insert a thermometer and the delivery tube, and heat to about 100°. Chlorine is obtained from a cylinder which is connected first to a filter flask, which acts as a trap, and then to the disperser. Rubber tubing (red) of 5 mm in diameter is used to make the connections between the filter flask and the disperser. Open the main valve of the cylinder first, making about one quarter turn, and then, very slowly, open the needle valve. Adjust the latter so a fine stream of bubbles issues through the disperser. Pass chlorine into the mixture slowly at first and increase the flow gradually. The flame is adjusted so that the heat from the reaction is sufficient to keep the temperature at 105-110°. Chlorine is passed into the mixture until the contents of the flask have gained about 150 g (85 per cent of theory) in weight. The time required is about nine hours. After six hours it is necessary to reduce the flow of chlorine. 

---