Over-saturation parameter

The results of the performed tests show that the reaction of equation (3) is easily promoted. However, the reaction of equation (4) occurs slower than the leaching reaction, and the silica then exists in an over-saturated concentration as shown in Figure 2(a). One may conclude that as it becomes more saturated, the silica is preferentially precipitated in a gel form, resulting in an adverse effect on the solid-liquid separation characteristics. In order to quantify this over-saturation parameter, we defined the value with the highest content of silica in solution as Max. Si02-Concentration . 

Soil redox also strongly affects solubility of the compounds of other trace elements in arid soils. Amrhein et al. (1993) found that Fe, Mn, Ni and V in an evaporation pond soil were more soluble under reducing conditions. Han and Banin (2000) reported that after one year of saturated incubation, the solubility of Fe, Mn, Co, V, Ni, Cu and Zn in two Israeli arid soils with 0.5-23% CaC03 increased, while the solubility of Cd decreased with time. During saturated incubation, soil pH in highly calcareous arid soil containing high content of carbonates decreased. In a loessial soil from Israel, Han and Banin (1996) reported that soil pH decreased from 8.0 to 7.0-7.4 over saturated incubation. With the decrease in Eh over incubation, the parameter pe+pH also decreased from initial values of 12-13.6 to 4 after initial 7-9 days of saturation incubation. 

All samples were characterized by x-ray diffraction (XRD) and by 29Si and 27A1 MAS NMR. The unit cell parameters, framework Si/Al ratios and the numbers of framework Si and A1 atoms per unit cell calculated from deconvolution using Gaussian peak shapes are given in Table n. All samples were fully hydrated over saturated NH4CI for 24 hours prior to NMR experiments. 

The range of practical crystallization processes carried out inside the important metastable area depends upon many process parameters, including solution concentration, intensity of mixing in the crystallizer, cooling rate, initial temperature, number of crystal seeds and the crystallizer shape (surface condition). In order to crystallize an over-saturated solution within the metastable area, inoculate crystals must be present when the solubility curve is crossed. If the crystal seeds are present when the metastable area is entered, the over-saturation of the solution will be reduced this is because the over-saturation is mainly used by the crystal seeds for growth although a few new crystal seeds are formed. Both crystal growth and seed formation occur and... 

Spreading over saturated porous substrate than in the case of dry spreading, (2) experimentally determined values of the effective lubrication coefficient, (o, agree well with the aforementioned theoretical estimations. However, precision of experimental determination of this parameter does not allow us to extract more information about effective viscosity of the porous substrate. 

Because both Tg and water activity are functions of water content, the two parameters can be correlated to each other. This can be done in two main ways, as presented by Roos (1995). The first is to measure Tg of samples humidified to known water activity values (i.e., using saturated salt solutions) and then plot Tg values as a function of water activity (e.g., see Figure 6.2A in Roos, 1995). Over the entire nw range, a sigmoid-shaped curve was... 

Using a recent equation of state of the van der Waals type developed to describe non-polar components, a model is presented which considers water as a mixture of monomers and a limited number of polymers formed by association. The parameters of the model are determined so as to describe the pure-component properties (vapour pressure, saturated volumes of both phases) of water and the phase equilibria (vapour-liquid and/or liquid-liquid) for binary systems with water including selected hydrocarbons and inorganic gases. The results obtained are satisfactory for a considerable variety of different types of system over a wide range of pressure and temperature. 

Biochemical oxygen demand (BOD) is one of the most widely determined parameters in managing organic pollution. The conventional BOD test includes a 5-day incubation period, so a more expeditious and reproducible method for assessment of this parameter is required. Trichosporon cutaneum, a microorganism formerly used in waste water treatment, has also been employed to construct a BOD biosensor. The dynamic system where the sensor was implemented consisted of a 0.1 M phosphate buffer at pH 7 saturated with dissolved oxygen which was transferred to a flow-cell at a rate of 1 mL/min. When the current reached a steady-state value, a sample was injected into the flow-cell at 0.2 mL/min. The steady-state current was found to be dependent on the BOD of the sample solution. After the sample was flushed from the flow-cell, the current of the microbial sensor gradually returned to its initial level. The response time of microbial sensors depends on the nature of the sample solution concerned. A linear relationship was foimd between the current difference (i.e. that between the initial and final steady-state currents) and the 5-day BOD assay of the standard solution up to 60 mg/L. The minimum measurable BOD was 3 mg/L. The current was reproducible within 6% of the relative error when a BOD of 40 mg/L was used over 10 experiments [128]. 

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