Methyl chloride heat capacity

Messerly, G.H., Aston, J.G. (1940) The heat capacity and entropy, heats of fusion and vaporization and the vapor pressure of methyl chloride. J. Am. Chem. Soc. 62, 886-890. 

Thermodynamic functions (entropy, heat capacity, enthalpy and free energy functions) have not been reported for 1,2,4-thiadiazoles. The ionization constants of a number of 1,2,4-thiadiazoIes have been determined potentiometrically or by Hammett s method (65AHC(5)ll9). Polarographic measurements of a series of methylated 5-amino-l,2,4-thiadiazoles show that thiadiazoles are not reducible in methanolic lithium chloride solution, while thiadiazolines are uniformly reduced at E0.s = -1.6 0.02 V. This technique has been used to assign structures to compounds which may exist theoretically as either thiadiazoles or thiadiazolines (65AHC(5)119). 

The so-called JANAF tables [6] are an excellent compilation of thermodynamic data in tabular form. Table 3.2 is an extract of the heat capacity data for methyl chloride over a range of temperatures. By drawing a simple graph of CP against T, and measuring the area, qP= CP AT may easily be determined. From Fig. 3.4 it is found that 41.76 kJ are needed to heat one mole of CH3C1 from 350 K to 1000 K. 

In an autoclave of 1-liter capacity, without stirrer, and heated by an oil bath, is placed 600 cc. dry methyl alcohol in which 23 grams of metallic sodium has previously been dissolved (reflux condenser), and to this is added 158 grams of pure o-nitrochlorobenzene (m.p. about 32°C. b.p. 243°). The autoclave is sealed and the heating is started. The temperature is raised to 120° over a period of 1 hour, held at this point for 3 hours, and finally held at 128° for 1 hour more. The pressure is 8 to 10 atmospheres. At the end of the reaction, the methyl alcohol is blown out through the valve into a good condenser. The recovered methyl alcohol can be used without purification in a subsequent run. The reaction product is removed from the autoclave, washing the latter out with hot water to remove the sodium chloride. The crude product is washed twice with five times its volume of hot water, separated, and distilled in vacuum. The yield is 136 grams, or 88 per cent of the theoretical amount. The product boils at 141° at 15 mm. 

Among these heat stabilisers, those containing tin (such as tin mercaptides, and tin carboxylates or maleates) are considered to be the most efficient, and can be used in a wide variety of applications. Metallic tin is harmless but there are suspicions that organotin-compounds can be toxic to the central nervous system and the liver. However, tin stabilisers have a low capacity for migrating, and hence they are still considered to be safe. Tin stabilisers such as methyl and octyl tins are used in food contact applications. For PVC, it is believed that tin stabilisers act as HCl scavengers (generating tin chloride) as well as an antioxidant. Thio-tin compounds (preferred for rigid pipe extrusions and profiles (for window frames) of PVC) may develop an odd odour due to sulfur. 

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