Temperature of Color

7 Practical Data for Ceramists and Refractory Engineers 10.5.7.1 Temperature of Color 

In practice, the temperature of an incandescent body can be estimated roughly from the color of radiation emitted according to a practical scale described in Table 10.18. 

Lowest visible red Lowest visible red to dark red Dark red to cherry red Cherry red to bright cherry red Bright cherry red to orange Orange to yellow Yellow to light yellow Light yellow to white White to dazzling white 

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Various measurements at varied conditions in equipment with filtered xenon arc radiation have shown a linear function between standard temperatures and level of irradiance (Boxhammer et. al 1993), and also that the surface temperatures of colored samples measured in equipment can be correlated to those under natural conditions (Figure 5.16) (Boxhammer, 1995). 

Because of the very nature of continuous spectra at the temperature of colored flames, it is not possible for photon energies to predominate in any one portion of the visible spectrum. Thus sources of continuous light emissions can not generate colored light and are always undesirable when attempting to produce deeply colored flames. 

Pyrotechnic flames always contain some solid or liquid particles, either ejected from the burning surface or as combustion products (smoke). At the temperatures of colored flame, these particles incandesce with near white light, reducing the purity of any colored light produced. 

Note at the temperatures of colored flames, when strontium atoms are ionized, it will only be to the +1 state and not the +2 state. 

Figure 11 Effect of increasing irradiance on temperature of colored samples in a Xe ueather-ometer. BPT = 70 C.

The front of the region in which the X centers formed, denoted by Xj in Fig. 1, varied with the time and temperature of coloration. The results of coloration for various times and temperatures are shown in Fig. 2. The... 

Fig. 3. Distribution of X centers from the surface of annealed crystals. Time and temperature of coloration and annealing are identical for each curve. Original thicknesses were approximately 2.6 mm.

Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289oC. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color. 

Furfural is very thermally stable in the absence of oxygen. At temperatures as high as 230°C, exposure for many hours is required to produce detectable changes in the physical properties of furfural, with the exception of color (17). However, accelerating rate calorimetric data shows that a temperature above 250°C, in a closed system, furfural will spontaneously and exothermically decompose to furan and carbon monoxide with a substantial increase in pressure. The pressure may increase to 5000 psi or more, sufficient to shatter the container (18). 

If food can be heated quickly to a temperature of I3I°C a lethaUty equivalent to 6 min at I2I°C can be accumulated in 36 s. This rapid heating and cooling of hquid foods, such as milk, can be performed in a heat exchanger and is known as high temperature—short time (HTST) processing. HTST processing can yield heat-preserved foods of superior quahty because heat-induced flavor, color, and nutrient losses are minimized. 

Fabric Composition. The method of fabric manufacture dictates many of the characteristics of the sheet, but intrinsic properties are firmly estabhshed by the base polymer selected. Properties such as fiber density, temperature resistance, chemical and light stabiUty, ease of coloration, surface energies, and others are a function of the base polymer. Thus, because nylon absorbs more moisture than polypropylene, spunbonded fabrics made from nylon are more water absorbent than fabrics of polypropylene. 

Safety Showers. Safety showers and eyewash fountains or hoses should be installed where corrosive or toxic materials are handled. A large-volume, low velocity discharge from directly overhead should effect continuous drenching, ie, a minimum flow of 20 L/min (50 gal /min). Water to outside showers may be heated to a maximum temperature of 27°C by an electric heating cable. The valves for all safety showers should be at the same height and relative position to the shower head, and they should operate in the same way and direction. The shower station should be identified by paint of a bright, contrasting color. In areas where chemicals harmful to the eyes may be encountered, an eyewash fountain or spray should be available in case of splash accidents. 

Storage tanks, lines, and pumps should be heat traced and insulated to enable product handling. Temperature control is required to prevent product degradation because of color alkan olamines have poor heat transfer properties. Exposure to air will also cause product discoloration. Storage tanks should be nitrogen-padded if low color product is required. 

Chlorendic anhydride is the common name of the Diels-Alder adduct of maleic anhydride and hexachlorocyclopentadiene, 3,4,5,6,7,7-hexachloroendomethylene-l,2,3,6-tetrahydrophthahc anhydride (HET). The resultant resins from HET contribute to the flame retardancy of the alkyd coatings. HET gives a greater reaction rate than phthaUc anhydride, to the extent that at 204—210°C the reaction rate approximates that of phthaUc anhydride at a temperature of 238°C (8). However, the resins tend to develop darker color, particularly at high processing temperature. Tetrachlorophthahc anhydride [117-08-8] made by conventional chlorination of phthaUc anhydride, would also impart flame retardancy to its alkyds. However, it is appreciably less soluble in the usual processing solvents than is phthaUc anhydride, and is reported to be of appreciably lower chemical reactivity (8). 

EDTA (ethylenediaminetetraacetic acid, [60-00-4]) chelates any trace metals that would otherwise decompose the hydrogen peroxide [7722-84-1]. The amine is preheated to 55—65°C and the hydrogen peroxide is added over one hour with agitation the temperature is maintained between 60 —70°C. The reaction is exothermic and cooling must be appHed to maintain the temperature below 70°C. After all the peroxide has been added, the temperature of the reaction mixture is raised to 75°C and held there from three to four hours until the unreacted amine is less than 2.0%. The solution is cooled and the unreacted hydrogen peroxide can be destroyed by addition of a stoichiometric amount of sodium bisulfite. This may not be desirable if a low colored product is desired, ia which case residual amounts of hydrogen peroxide enhance long-term color stabiUty. 

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