Gypsum 686 Subject

The coefficient Tj is termed the modulus of rigidity. The viscosities of thixotropic fluids fall with time when subjected to a constant rate of strain, but recover upon standing. This behavior is associated with the reversible breakdown of stmctures within the fluid which are gradually reestabflshed upon cessation of shear. The smooth sprea ding of paint following the intense shear of a bmsh or spray is an example of thixotropic behavior. When viscosity rises with time at constant rate of strain, the fluid is termed rheopectic. This behavior is much less common but is found in some clay suspensions, gypsum suspensions, and certain sols. 

The second principal advantage is that CYANEX 272 is the only one of the three above-mentioned compounds that extracts cobalt in preference to calcium (52). This property can minimise or eliminate the solvent losses that are associated with calcium extraction and the subsequent precipitation of gypsum cmds in the scmbbing or stripping circuits. This is illustrated in Eigure 1 where calcium extraction is shown as a function of pH for the three subject reagents. 

Common pollutants in a titanium dioxide plant include heavy metals, titanium dioxide, sulfur trioxide, sulfur dioxide, sodium sulfate, sulfuric acid, and unreacted iron. Most of the metals are removed by alkaline precipitation as metallic hydroxides, carbonates, and sulfides. The resulting solution is subjected to flotation, settling, filtration, and centrifugation to treat the wastewater to acceptable standards. In the sulfate process, the wastewater is sent to the treatment pond, where most of the heavy metals are precipitated. The precipitate is washed and filtered to produce pure gypsum crystals. All other streams of wastewater are treated in similar ponds with calcium sulfate before being neutralized with calcium carbonate in a reactor. The effluent from the reactor is sent to clarifiers and the solid in the underflow is filtered and concentrated. The clarifier overflow is mixed with other process wastewaters and is then neutralized before discharge. 

Gypsum Saturation from Measurements of Dissolved SOg. Use of measurements of dissolved calcium to determine gypsum saturation is relatively easy from a computational standpoint use of measurements of dissolved SO2 is more difficult. However, wet chemical analyses for calcium are frequently subject to interference by high concentrations of magnesium. For installations where a quick and reliable analysis for calcium is not available, the use of dissolved SO2 is preferred, and the following correlation applies ... 

The equilibrium diagram (2, p. 274 6) for the species in Equation (13.16) is shown in Figure 13.7. If gypsum and anhydrite are both under liquid water at 1 bar, then equUibrium can be attained only at 40°C (see Fig. 13.7). If the hquid pressure is increased, and the rock formation is completely impermeable to the hquid phase, so that the pressure on the fluid phase is equal to the pressure on the sohd phase, then the temperature at which the two solids, both subject to this hquid pressure, are in equUibrium is given by the curve with positive slope on the right side of Figure 13.7. Thus, the right curve apphes to any situation in which Pp is equal to Ps- Under these conditions, the net AV , for the transformation of Equation (13.16) is 36.14 29.48 = 6.66 cm [see Equations (13.18) and (13.19)],... 

The C3A phase is subjected to competitive reaction between water and gypsum to form a small amount of the initial C3A hydrates covered by a protective coating of ettringite, and also a proportion of the C3S hydrates to form a calcium silicate hydrate of low calcium content in the region of 100 nm thick. 

The thermodynamic properties of gypsum decomposition, which involve two distinct steps, have been the subject of much theoretical and practical study. Two forms of the hemihydrate. a and ft. have been identified. 

TOTHUS — A White Gypsum-like Substance, resembling Dead Ashes. It is that Matter which forms about the joints of the bones in those persons who are subject to violent attacks of Gout. 

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