Phase calcium/magnesium

Phase diagrams for the systems calcium/ magnesium and H20/HF formation of one and three compounds, respectively... 

Not all of the salt constituents are found in the dissolved state in milk. Calcium, magnesium, phosphate, and citrate are partitioned between the solution phase and the colloidal casein micelles (see Chapter 9 for the composition and structure of these micelles). For analytical purposes, partition of the salt constituents can be achieved by equilibrium dialysis or by pressure ultrafiltration. In the latter technique, pressures must be limited to about 1 atmosphere to avoid the so-called sieving effect (pushing water through the filter faster than the dissolved components (Davies and White 1960). 

The procedure used to define an equilibrium model is to (1) define all the variables and (2) define independent equilibria as a function of phase equilibria. The variables are defined as the chemical parameters typically measured in water chemistry. For the major constituents and some of the more important minor constituents, these are calcium, magnesium, sodium, potassium, silica, sulfate, chloride, and phosphate concentrations as well as alkalinity (usually carbonate alkalinity) and pH. To this list we would also add temperature and pressure. The phase equilibria are defined by compiling well-known equilibria between gas-liquid phases and solid-liquid equilibria for the solids commonly found forming in nature in sedimentary rocks. Within this framework, one can construct different equilibrium models depending upon the mineral chosen actual data concerning the formation of specific minerals therefore must be ascertained to specify a particular model as valid. 

The main crystalline phases were identified (see Figs. 1 2) and the contents of amorphous material were determined from selected bed samples by XRD. Main crystalline phases are Ca9(Al 0 g) calcium aluminium oxide, Ca8,2sNai.5(Al60]g) calcium sodium aluminium oxide, calcium magnesium silicate (diopside), calcium phosphide, and magnesium silicate (enstatite). 

Once the cells have reached the exponential phase in the growth cycle, the levels of calcium, magnesium, and manganese increased, iron remained approximately constant, and the other metals decreased (aluminum, cadmium, copper, chromium, lead, silver, and zinc). During this... 

Equilibrium reactions among all the calcium-magnesium carbonates can be written in terms of the CO2 pressure and mCa VmMg ratio in water ([H2O] = 1). A diagram in which the phase bound-... 

Another interesting role of citic acid observed during in vitro calcification was to prevent the involvement of magnesium in the formation of calcium phosphate deposits. Magnesium has been known to stabilize the calcium phosphates, e.g. in the form of whitlockite phase. Thus magnesium inhibits the transformation of these calcium phosphate deposits into hydroxyapatites (33, 43,44). 

Usually when reaction paths are simulated, the irreversible reactant is an unstable mineral or a suite of unstable minerals that is, the stoichiometry of the irreversible reaction is fixed. Evaporation poses a special problem in reaction path simulation because the stoichiometry of the irreversible reaction (defined by the aqueous solution composition) continually changes as other minerals precipitate (or dissolve). In the second problem (above) evaporation of seawater was simulated by irreversible addition of "sea salt", that is, a hypothetical solid containing calcium, magnesium, sodium, potassium, chloride, sulfate and carbon in stoichiometric proportion to seawater. The approach used was valid as long as intermediate details of the reaction path are not required. The reaction path during evaporation could be solved in PHRQPITZ by changing the stoichiometry of the irreversible reactant (altered "sea salt") incrementally between phase boundaries, but this method would be extremely laborious. 

During the evaporation of the brines, the toxic element strontium is accumulated in the liquid phase, to a maximum of 6.24 kg m Sr at the beginning of the calcium-magnesium chloride sedimentation with the strontium decreasing in the brine. During the evaporation process of the exhaust brine at the Nebitdag iodine plant the strontium ion is distributed as follows ... 

Borates with zinc, calcium, magnesium, melamine or barium as the cation, combine char formation with endothermic decomposition as a dual mechanism that provides an efficient flame retardant system. Although the exotherm reduction is not as great as that achieved with ATH, there is enough endotherm to delay the initiation of the polymer exotherm by as much as 100 °C in some systems. It is this endothermic reaction in the polymer condensed phase and the formation of a glassy char that makes borate products good s mergists with the fire retardant antimony trioxide. 80% of the boron from zinc borate remains in the char after PVC combustion. 

As mentioned in the previous sections, surfactants are included in acid formulations to perform specific tasks. In acid stimulation treatments, surfactants encounter various chemical species. First, the surfactant is mixed with the acid and its additives. Some of these additives are cationic, e.g., corrosion inhibitors and clay stabilizers. Others are anionic or nonionic species. Second, the acid reacts with the formation and releases several cations. Hydrochloric acid reacts with carbonate minerals and, as a result, the spent acid contains calcium, magnesium and iron. Hydrofluoric-based acids react with clay minerals and release silicon and aluminum in addition to those dissolved by hydrochloric acid. The presence of these chemicals together with surfactants can cause phase separation of the surfactants. As a result, surfactants will not perform their task as anticipated. 

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