Heat continued

Thermal Properties. Thermal properties include heat-deflection temperature (HDT), specific heat, continuous use temperature, thermal conductivity, coefficient of thermal expansion, and flammability ratings. Heat-deflection temperature is a measure of the minimum temperature that results in a specified deformation of a plastic beam under loads of 1.82 or 0.46 N/mm (264 or 67 psi, respectively). Eor an unreinforced plastic, this is typically ca 20°C below the glass-transition temperature, T, at which the molecular mobility is altered. Sometimes confused with HDT is the UL Thermal Index, which Underwriters Laboratories estabflshed as a safe continuous operation temperature for apparatus made of plastics (37). Typically, UL temperature indexes are significantly lower than HDTs. Specific heat and thermal conductivity relate to insulating properties. The coefficient of thermal expansion is an important component of mold shrinkage and must be considered when designing composite stmctures. 

FIG. 12-78 Indirect-heated continuous plate dryer for atmospheric, gastight, or fuU-vacuum operation. (Krauss Maffei.)... 

Wet in % of dry Ultraviolet Light Resistance Resistance to Fungus, Rot, and Mildew Resistance to Dry Heat Continuous OF... 

Chromatogram zones are produced that are initially pink but turn blue as the heating continues they are on a pale blue background. 

A mixture of a-naphthol 41 (15.0 g, 0.1 mol), phenylhydrazine 42 (11.0 g, 0.1 mol) and sodium bisulfite solution (36 %, 250 g) was heated at reflux for 15 h. A further 4 g of phenylhydrazine was added and heating continued for 15 h, after which time the majority of the a-naphthol was consumed. After cooling, the mixture was extracted with ether. The oily, ether and aqueous insoluble residue was warmed with cone. HCl until a dark crystalline mass developed. After cooling, the mixture was extracted with ether. The organic extract was dried and concentrated to afford a crystalline residue which was purified by recrystallisation from ethanol to afford the product 43 as a white crystalline solid, mp 225 °C. A reaction yield is not given. 

About 1 gram of ben2aldehyde is healed in a retort with 40 c.c. of oouceutratod salphurio acid, the fumes collected iu a solution of silver nitrate, and the heating continued anti] no further precipitate insoluble in hot dilute nitric acid is obtained in the silver nitrate solution. Tbie takes about three hour, ... 

A final addition of 2 g. of iron powder is made, and the heating continued for one hour longer. 

Hicks showed that the time required to achieve ignition depends on the manner in which the external heat flux is applied. If the propellant surface is heated continuously, the surface temperature will continue to rise until runaway reaction conditions are reached [curve (a) of Fig. 3]. If the heat flux is terminated just before runaway reaction conditions pre achieved, then a sudden drop in surface temperature can occur, followed by a long time-delay before the surface temperature again begins to mse [as shown in curve (b)]. If the flux is removed too soon, the temperature will drop continuously and ignition will not be achieved [as shown in curve (c)]. 

Once their boiling points are reached, heating continues for... 

Provision of emergency cooling systems for reactors, where heat continues to be generated after shut-down for instance, in some polymerisation systems. 

Another alternate synthetic method for the manufacturing of niclosamide is reported [1], Phosphorus trichloride (PC13) is slowly introduced into a boiling xylene solution containing 5-chlorosalicylic acid and 2-chloro-4-nitroaniline in equimolar ratio and the heating continued for 3 h. Crystals of niclosamide separate on cooling and are recrystallized from ethanol [7,8], van Tonder et al. [9] prepared and characterized three crystal forms of niclosamide namely the anhydrate and the two monohydrates. 

Temperature Heated continuously Only during raising... 

Fig. 4.5 Temperature gradients within a microwave-heated microtiter plate 1 mL per well, heated continuously for 1 min at full power in a conventional microwave oven. Adapted from [90].

Typical procedure A suspension of 0.070 g (0.55 mmol) of tellurium metal and 0.24 g (1.05 mmol) of anhydrous chloramine-T in 2 mL of toluene was heated at reflux for 1 h, at which time the suspension became grey. The aldehyde (1.0 mmol) was added and heating continued (1 h). The grey suspension became white. Methylene chloride was added and the reaction filtered through Celite . Removal of solvent in vacuo gave the iV-tosyli-mine suitable for further use. Analytical samples were purified by recrystallization or flash chromatography. 

---