White-point temperature

ISO 2115-1996 and equivalent BS2782, method 740C, Polymer dispersions— Determination of white point temperature and minimum film forming temperature. 

As an aqueous dispersion can only dry above 0 °C, the MFFT and white-point temperature are only defined above this value. The control of the polymer layer thickness is crucial for the measurements. Mechanical stress may develop during film formation (particularly when crosslinking is involved) which leads to crack formation above a certain layer thickness. A further point which should be considered is that very short drying times are often used in dispersion processing, for example on coating machines. In this case, the MFFT may well he above the value determined according to ISO 2115. The discrepancy is caused by kinetic limitations in water evaporation and polymer interdiffusion [24]. 

Potassium hydroxide is the principal electrolyte of choice for the above batteries because of its compatibiUty with the various electrodes, good conductivity, and low freezing point temperature. Potassium hydroxide is a white crystalline substance having a mol wt = 56.10 density = 2.044 g/mL, and mp = 360° C (see Potassium compounds). It is hygroscopic and very soluble in water. The most conductive aqueous solution at 25 °C is at 27% KOH, but the conductivity characteristics are relatively flat over a broad range of concentrations. 

The injection sequence, which results in a highly sooting flame (Fig. 6.13), occurs out of phase with the air vortex formation. The first fuel injection misses the air vortex and stays unmixed while also partially suppressing the roll-up of this air vortex. The second-fuel injection enters the void between the air vortices and stays separated from the air. The rich mixture results in the formation of soot at this point as shown by the white spots. Temperature profiles also show the energy release rate to be lower in this case. 

Fig. 14 Creation of a single specimen polymer blend phase diagram from orthogonal polymer composition and temperature gradients. The polymers are polystyrene and poly(vinyl methyl ether) (PVME) a composition library placed orthogonal to a temperature gradient b completed gradient library polymer blend phase diagram. White points are data derived from traditional measurement for comparison. See text for details, (b reproduced with permission from [3])...

Figure 6. Time-series depth profiles of ammonium, nitrate, and temperature in the inshore region (Stations 47, 55, 58, 62, 69, and 70) and the offshore region (Stations 48, 56, 59, 67, and 71) between Long Point and Whites Point off Los...

The solvent is removed under continuous vacuum (0.1 mm) at room temperature, and most of the excess I2 can be pumped off at this point. To remove residual amounts of l2,t the crude solid is transferred to a sublimator and gently heated from 25 to 50° under continuous vacuum with no working cold finger. When the solid appears nearly white, the temperature is raised to 85°, and the pure [Re(CO)5l] is sublimed at 0.1 mm. The compound suUimes to a milky-white crystalline solid. Yield 0.82 g (80.2%) based on [Re2(CO)io]. 

Fig. 2.29 Optical microscopy photograph of a PS and poly(vinyl methyl ether) (PS/PVME) T-(j> combinatorial sample (library) after 16 h of annealing, showing the lower critical solution temperature (LCST) cloud-point curve. White points are conventional /ight-scattering cloud points measured independently on separate uniform samples (Meredith et al. 2000)...

When the illuminant source is taken into consideration, even more information can be extracted. Figure 11.7 is the same as 11.6 with the addition of the incandescence curve superimposed over the chromatidty chart. The curve shows the temperature of the illuminant and a few of the available CIE standard illuminants such as D65 (daylight 6500K equivalent). The white point W is also called achromatic since it consists of equal amounts of RGB and is perceived as white. Utilizing the incandescence curve and the chromatidty coordinates, additional information and descriptors of a color can be obtained. 

Mix 42 5 g. of acetone cyanohydrin (Section 111,75) and 75 g. of freshly powdered ammonium carbonate in a small beaker, warm the mixture on a water bath FUME CUPBOARD) and stir with a thermometer. Gentle action commences at 50° and continues during about 3 hours at 70-80°. To complete the reaction, raise the temperature to 90° and maintain it at this point until the mixture is quiescent (ca. 30 minutes). The colourless (or pale yellow) residue solidifies on coohng. Dissolve it in 60 ml. of hot water, digest with a little decolourising carbon, and filter rapidly through a pre-heated Buchner funnel. Evaporate the filtrate on a hot plate until crystals appear on the surface of the liquid, and then cool in ice. Filter off the white crystals with suction, drain well, and then wash twice with 4 ml. portions of ether this crop of crystals of dimethylhydantoin is almost pure and melts at 176°. Concentrate the mother liquor to the crj staUisation point, cool in ice, and collect the... 

Sodamide. Assemble the apparatus shown in Fig. VI, 16, 1, a. Fill the bath to a point about half-way up the side of the flask with methyl alcohol (or methylated spirit) and add solid carbon dioxide (Dry Ice or Drikold) in lump form until a white frost commences to form on the outside of the bath (2) the bath temperature should be about — 35 . 

Ethylene. Under the influence of pressure and a catalyst, ethylene yields a white, tough but flexible waxy sohd, known as Polythene. Polyethylene possesses excellent electric insulation properties and high water resistance it has a low specific gravity and a low softening point (about 110°). The chemical inertness oi Polythene has found application in the manufacture of many items of apparatus for the laboratory. It is a useful lubricant for ground glass connexions, particularly at relatively high temperatures. 

The metal is silvery white and at red heat slowly changes in air to the resquioxide. At higher temperatures it converts back to the element. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. 

Barium fluoride [7782-32-8] Bap2, is a white crystal or powder. Under the microscope crystals may be clear and colorless. Reported melting points vary from 1290 (1) to 1355°C (2), including values of 1301 (3) and 1353°C (4). Differences may result from impurities, reaction with containers, or inaccurate temperature measurements. The heat of fusion is 28 kj/mol (6.8 kcal/mol) (5), the boiling point 2260°C (6), and the density 4.9 g/cm. The solubiUty in water is about 1.6 g/L at 25°C and 5.6 g/100 g (7) in anhydrous hydrogen fluoride. Several preparations for barium fluoride have been reported (8—10). 

Upon heating, a-white phosphorus first melts, then either vaporizes or converts to amorphous red phosphoms. The conversion to red P proceeds slowly in one to two days at temperatures slightly below the 280°C boiling point of Hquid P. The product is amorphous to x-ray diffraction. 

Physical and Chemical Properties. Trimellitic acid and trimellitic anhydride are odorless white crystalline soHds in their pure form. The acid is reasonably stable up to the melting point, where dehydration to the anhydride occurs. The anhydride reacts with atmopsheric moisture, even at room temperature, to revert to the acid. Physical properties of the acid and its anhydride are Hsted in Tables 29—31. 

The normal salt, CH COONH, is a white, deUquescent, crystalline soHd, formula wt 77.08, having a specific gravity of 1.073. It is quite soluble in water or ethanol 148 g dissolve in 100 g of water at 4°C. The salt s solubiUty in water increases only slightly as temperature increases up to about 25 °C. The specific gravity of aqueous neutral ammonium acetate ranges from 1.022 to 1.092 as solution concentration increases from 10 to 50 wt % (4). The normal salt melts at 114°C, but decomposes before reaching its boiling point. 

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