Slow heating rates

Instrumental factors. Heating rate. When a substance is heated at a fast rate, the temperature of decomposition will be higher than that obtained at a slower rate of heating. The effect is shown for a single-step reaction in Fig. 11.4. The curve AB represents the decomposition curve at a slow heating rate, whereas the curve CD is that due to the faster heating rate. If TA and Tc are the decomposition temperatures at the start of the reaction and the final temperatures on completion of the decomposition are TB and TD, the following features can be noted ... 

Contamination of metal with other distillates is largely overcome when reducing selected compounds with Zr since the alkali metal is then the only volatile species. Mixtures of CSHSO4 and Cs2Cr04 react explosively, however, carrying particulates over, unless slow heating rates and a large excess of Zr are employed. 

Measurements of melting curves can be used to obtain very accurate evaluations of the melting point of a compound when slow heating rates are used. The phase transition can also be monitored visually, with the operator marking the onset and completion of the melting process. This is most appropriately performed in conjunction with optical microscopy, thus yielding the combined method of thermomicroscopy or hot-stage microscopy [7]. 

Cured Olixomer Properties. The T, of the cured specimen ms not obvious by DSC, however the T was observed at 383°C (Q maac) by dynamic mechanical testing of a torsion bar. The T obtained by this method has been driven up in temperature by the slow heating rate of 2°C/minute used in the test, the actual T is somewhat lower... 

When the reaction was performed at 50°C in the presence of Na2S04 (12.5 wt%/ starch), the granular aspect of starch was completely preserved, especially with a final slow heating rate of 0.2°C/min and similar DS of 0.07 was obtained, indicating that Na2S04 did not affect the catalytic performance of the system. 

It is frequently the case that organic peroxides, and the hydroperoxides in particular, cannot be analyzed by GLC in the usual way, as they undergo decomposition inside the instrument. A study on the thermal stability of various organic peroxides shows that on using the cold on-column injection technique, with the temperatures of the injection port and column as low as practically possible and applying slow heating rates, it is possible to... 

Fig. 5.15 (a) Field ion image and a domain map of a N Mo alloy which has been annealed for 5 min at 800°C with a slow heating rate to the final annealing temperature. Long range ordered domains are formed within the disordered matrix which, however, already exhibits a small degree of short range order. (Courtesy of M. Yamamoto.)... 

Usually 1-2 days (for reactors on this scale) of experimental effort are required to traverse the loop as shown in Figure 3.1b. In order to avoid obtaining an erroneous dissociation temperature and pressure, the dissociation part of the loop must be performed at a sufficiently slow heating rate (about 0.12 K/h) to allow the system to reach equilibrium (Tohidi et al., 2000 Rovetto et al., 2006). The temperature difference between the temperature at Point D to that at Point B is called the subcooling [more properly the supercooling, ArSUb, where AFsub = 7eqm(D) — T (B)]. 

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