Avoid Melts

Since graphite is a very strong absorber of microwave heating, the temperature must be carefully controlled to avoid melting of the reactor. The use of a quartz reactor is highly preferable. 

During the lyophilizing process, the sample has to get external heat because sublimation of ice withdraws heat resulting in cooling the probe, but avoid melting of the sample. 

To reduce exposures, high-power X-ray tubes have been developed the limiting factor here is the heat generated at the focal spot on the target. To avoid melting, the target is rotated so that the heat is spread over an increased area (Muller, 1929 Astbury and Preston, 1934 Peiser, Rooksby, and Wilson, 1955). 

In flame treatment, an oxidizing flame is deployed so as to impinge on the surface for a very short time (thus avoiding melting the plastic). As time is... 

Commercially, separation is mostly performed by vacuum filtration on belt or drum filters or by pressure in membrane filters (Illingworth, 2002). Evenly-sized well-developed spherical crystals, such as those obtained in a well-executed Tirtiaux process, can be easily recovered using vacuum filters. For optimal filtration, the air on top of the filter may be cooled or heated to the filtration temperature to avoid melting or crystallization on the filter and clogging of the filter cake. This results in increasing entrainment and reducing filter speed. A considerable amount of oil is entrained in the filter cake, which can be as much as 60-70% for milk fat. 

Great care must be exercised to avoid melting more glass than is absolutely necessary to effect the join. The bore of the melted glass must not be allowed to constrict by more than about 0.5 mm, nor should it be blown up to more than 0.5 mm above that of the capillary. Annealing follows the normal practice. (See Fig. 6.27.)... 

In the other method, the tubes are joined to the constrictions before the bulb is blown. This method makes a neater job, but extra care must be exercised to avoid melting the relatively small diameter tubes when the glass for the bulb is being heated and gathered (Fig. 6.40e, f). 

Solution correlate residual solvent content ( wetness ) and dryer temperature to avoid melt-down. 

While the diazotization is in process, 68 g. (i.i moles) of boric acid is dissolved in 133 g. (4 moles) of 60 per cent hydrofluoric acid (Note 2) in a beaker coated with paraffin-wax. The temperature is kept below 25° to avoid melting the paraffin-wax (Note 3). 

To avoid melt fracture in the potyetltylene extrusion described in Problem 7.18, the maximum elon tional strain-rate in the die must not exceed 10 s The die is therefore provided with a conically tapering entrance channel of half-angle a. Estimate the maximum allowable value of a, and comment on aity approximations used (see 7.N.1). 

In blown film extrusion, the barrel temperatures are relatively low, which permits fast production rates without raising the frost hne too high. Sufficient barrel temperature is required for good optical properties, that is, to avoid melt fracture, unmelted polymer, and other defects. However, if the barrel temperature or melt temperature is too high, the viscosity becomes too low, and the bubble becomes unstable and may... 

Purify the solid by dissolving it in hot 95% ethanol in a small Erlenmeyer flask (about 5 mL per 0.5 g of product) using a hot plate as the heating source. Be careful not to melt the solid on the hot plate. You can avoid melting the benzil by occasionally lifting the flask from the hot plate and swirling the contents of the flask. You want the solid to dissolve in the hot solvent rather than melt. You will obtain better... 

Purify Compound 1 by crystallization. See "Testing Solvents for Crystallization," Technique 11, Section 11.6, for instructions on how to determine an appropriate solvent. You should try 95% ethanol and xylene. After determining the best solvent, crystallize the compound using a hot water bath at about 70°C for heating to avoid melting the solid. Identify Compound 1 using some or all of the techniques given next in the section "Identification of Compounds."... 

Temperature limit for fuel (°C) 1100 (to avoid melting)/750 (to avoid eutectic reaction)... 

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