Working temperature

Mix 200 g. of adipic acid intimately with 10 g. of finely-powdered, crystallised barium hydroxide. Place the mixture in a 1-litre distilling flask, fitted with a thermometer reaching to within 5 mm. of the bottom connect the flask with a condenser and receiver. Heat the mixture gradually in an air bath (1) to 285-295° during about 90 minutes and maintain it at this temperature mitil only a small amount of dry residue remains in the flask this requires a further 2 hours. The temperature must not be allowed to rise above 300°, since at this temperature the adipic acid distils quite rapidly the best working temperature is 290°. The cycZopentanone distils slowly accompanied by a little adipic acid. Separate the ketone from the water in the distillate, and dry it with anhydrous potassium carbonate this treatment simultaneously removes the traces of adipic acid present. Finally distil from a flask of suitable size and collect the cycZopentanone at 128-131°. The yield is 92 g. 

Use the apparatus described in Section 111,72 and adjust the furnace for a working temperature of 400-450°. Although a manganous oxide catalyst gives satisfactory results, thoria is more convenient in practice. 

As already mentioned, the choice of the supercooled liquid as reference state has been questioned by some workers who use the saturation vapour pressure of the solid, which is measured at the working temperature in the course of the isotherm determination. The effect of this alternative choice of p° on the value of a for argon adsorbed on a number of oxide samples, covering a wide range of surface areas, is clear from Table 2.11 the average value of is seen to be somewhat higher, i.e. 18 OA. ... 

The working temperature, 77 K, is well below the triple point of krypton, 116 K, but if the solid is taken as the reference state the isotherm shows an unusually sharp upward turn at the high-pressure end. The usual practice, following Beebe, is therefore to take p° as the saturation vapour pressure of the supereooled liquid (p° = 2-49 Torr at 77-35 K and 27-5 Torr at 90-2 K). 

Upper working temperatures (Mechanical considerations only)... 

The formation of acids from heteroatoms creates a corrosion problem. At the working temperatures, stainless steels are easily corroded by the acids. Even platinum and gold are not immune to corrosion. One solution is to add sodium hydroxide to the reactant mixture to neutralize the acids as they form. However, because the dielectric constant of water is low at the temperatures and pressure in use, the salts formed have low solubiHty at the supercritical temperatures and tend to precipitate and plug reaction tubes. Most hydrothermal processing is oxidation, and has been called supercritical water oxidation. 

Joining material used in joints Working temperatures, < F Maximum working pressure, Ibf/in ... 

These values are restricted by 10°C, compared to the working temperature prescribed for standard motors, as in Table 9.1. 

Table 9.1 Maximum/permissible working temperatures lor different insulating materials...

These grades possess a high dr op point, of the order of 180°C, and a working temperature range from -30"C to + I30°C. 

Now, as we have said, there is only at most 20% Cr in the alloy, and the alloy behaves only partly as if it were protected by Cr203. In fact, experimentally, we find that 20% Cr increases the time for a given metal loss by only about ten times, i.e. the time taken to lose 0.1 mm at blade working temperature becomes 600 X 10 hours = 6000 hours rather than 10 hours. 

Fig. 11.3. Microstructures during the slow cooling of a eutectoid steel from the hot working temperature. As a point of detail, when peorlite is cooled to room temperature, the concentration of carbon in the a decreases slightly, following the a/a + FejC boundary. The excess carbon reacts with iron at the or-FejC interfaces to form more FejC. This "plates out" on the surfaces of the existing FejC plates which become very slightly thicker. The composition of Fe3C is independent of temperature, of course.

Fig. 11.4. Microstructures during the slow cooling of a hypoeutectoid steel from the hot working temperature. A3 is the standard labelling for the temperature at which or first appears, and A, is standard for the eutectoid temperature. Hypoeutectoid means that the carbon content is below that of a eutectoid steel (in the same sense that hypodermic means "under the skin" ).

Table 8.2 Working temperatures of cryogenic slush baths ...

These three criteria—molar mass interval, eluent, and working temperature—are fixed by the group of samples to be analyzed and considerably restrict the number of suitable columns. The selection has to be done from current lists of the manufucturers. It is useless to collect these data here, as such tables would be antiquated before this book is printed. This chapter deals with the quality of the selected columns. At this stage, columns of the same application profile are compared. The most important properties are (1) the number of... 

Glass wool products have a limiting temperature of 540°C but are mostly used in buildings and H V applications where a limiting working temperature of 230°C is recommended. 

Gas burners should comply with the relevant Codes of Practice, depending on whether the plant is low or high temperature. Low-temperature plant is defined as that having a normal working temperature insufficient to ignite the fuel, that is, below 750°C at the working temperature walls. The British Gas Codes of Practice are ... 

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