Calcium precipitate formation

In normal operations, there is little chance for spent acid to contact the completion fluid as the well will usually be produced after perforation, effecting the removal of completion fluid prior to acidization. The fact that a calcium precipitation reaction can occur should be recognized by those using TKPP solutions as a clear completion fluid in well operations. A KC1 spacer is recommended to avoid completion problems in formations having high calcium brines. 

Admixture incompatibilities - Magnesium sulfate in solution may result in a precipitate formation when mixed with solutions containing Alcohol (in high concentrations) alkali carbonates and bicarbonates alkali hydroxides arsenates barium calcium clindamycin phosphate heavy metals hydrocortisone sodium succinate phosphates polymyxin B sulfate procaine hydrochloride salicylates strontium tartrates. 

Fluoride is a natural component of most types of soil, in which it is mainly bound in complexes and not readily leached. The major source of free fluoride ion in soil is the weathering and dissolution of fluoride rich rock that depends on the natural solubility of the fluoride compound in question, pH, and the presence of other minerals and compounds and of water. The major parameters that control fluoride fixation in soil through adsorption, anion exchange, precipitation, formation of mixed solids and complexes are aluminium, calcium, iron, pH, organic matter and clay [19,20]. 

Separation-layer micro mixers are specially tools for mixing solutions which react fast or tend to foul otherwise [39, 53, 135-138], The most prominent example of such processes is probably the generation of particles by immediate precipitation, as e.g. for calcium carbonate formation. Separation-layer mixers thus overcome the limits of normal micro mixers, which tend to clog under such conditions. 

M 54] [P 48] Separation-layer micro mixers with concentric multi-layered outlets can be operated in a droplet-forming mode [53] If fast precipitating solutions are contacted in this way with a solvent layer for initial separation, the part of the droplet close to the tube outlets remains transparent, which demonstrates that a tri-layered system still exists with the two reacting solutions not being intermixed, as evidenced by calcium carbonate formation in aqueous solutions as described in [39,136], At the droplet end cap the layers collide and circulation flow sets in. As a result, mixing is achieved and precipitation occurs. The circulation patterns are visualized by the particle trajectories. 

Jordan M, Schallhorn A, Wurm FM (1996), Transfecting mammalian cells optimization of critical parameters affecting calcium phosphate precipitate formation, Nucleic Acids Res. 24 596-601. 

Strelyuk described a thin-layer chromatographic method for the qualitative detection of dipyridamole [62], Data were presented on the use of various reagents for the detection by solution color change and precipitate formation in the thin-layer chromatography of dipyridamole. Thin-layer chromatography was on silica gel-calcium sulfate dihydrate, with methanol aqueous ammonia or benzene-dioxane being used as the mobile phase with detection at 270-330 nm. The Rvalues were 0.7-0.75 and 0.5-0.55 for the two solvent systems, and the detection limit was... 

Extracellular calcium carbonate formation by some cyanobacteria and algae, which are photo synthetic autotrophs that obtain their carbon from CO2, can be explained by Eq. (1.5) above. In that instance, the uptake and fixation of CO2 by the cyanobacteria and algae promotes C03 formation needed for precipitation of extracellular CaC03. In the cyanobacterium Synechococcus, the Ca precipitated by C03 from photosynthesis is derived from that bound to the cell surface of Synechococcus (Thompson et al., 1990). 

Chronic megadoses of vitamin C may precipitate formation of calcium oxalate renal stones, oxalate nephropathy, and renal failure. The amount required to cause this is variable from 2 to 8gday . Bone oxalate deposits have also been reported. Esophageal and dental erosion are possible with tablet ingestion. Heinz body hemolytic anemia has been seen in premature infants. 

Oceanic surface water is everywhere supersaturated with respect to the two solid calcium carbonate species calcite and aragonite. Nevertheless, calcium precipitation is exclusively controlled by biological processes, specifically the formation of hard parts (shells, skeletal parts, etc.). The very few existing amounts of spontaneous inorganic precipitation of CaC03(s) come from the Bahamas region of the Caribbean. 

D. Precipitate formation effectively decreases available calcium ion. Because of widespread consumption of soft drinks rather than water by school age children aided by school vending machines, this consequence is of concern. 

From a knowledge of the solubility rules (see Section 4.2) and the solubility products listed in Table 16.2, we can predict whether a precipitate will form when we mix two solutions or add a soluble compound to a solution. This ability often has practical value. In industrial and laboratory preparations, we can adjust the concentrations of ions until the ion product exceeds K p in order to obtain a given compound (in the form of a precipitate). The ability to predict precipitation reactions is also useful in medicine. For example, kidney stones, which can be extremely painful, consist largely of calcium oxalate, CaC204 (K p = 2.3 X 10 ). The normal physiological concentration of calcium ions in blood plasma is about 5 mM (1 mM = 1 X 10 M). Oxalate ions ( 204 ), derived from oxalic acid present in many vegetables such as rhubarb and spinach, react with the calcium ions to form insoluble calcium oxalate, which can gradually build up in the kidneys. Proper adjustment of a patient s diet can help to reduce precipitate formation. Example 16.10 illustrates the steps involved in precipitation reactions. 

Although calcium carbonate formation in soil is a result of high evapotranspiration rates relative to precipitation rates, the term evaporite is usually restricted to compounds more soluble than CaCC>3. Where drainage water from surrounding soils accumulates and where the amount of percolated water is small compared to the amount of water evaporated, soluble salts tend to accumulate. This subject is dealt with in more detail in Chapter 11. The present section is restricted to the extreme case of natural salt flats and play as (former and intermittent lake beds). 

X 10 mol dni for magnesium oxalate). However, in the case of the calcium salt, precipitation is complete within a few minutes while the magnesium salt takes several hours. This difference in rates may even be used as a basis for the quantitative removal of calcium from solution without interference from magnesium. In order to expedite precipitate formation it is necessary first to look more closely at the processes by which precipitates are produced. 

Mates of Precipitate Formation and Particle Growth The rate at which a precipitate can be produced in a filterable form varies widely and depends upon the solution environment. In the case of the oxalates of calcium and magnesium for instance, both compounds have fairly low solubility products (2.3 x I0 mol dm for calcium oxalate and... 

Two possible roles of urate in calcium stone formation have been suggested. One is stone formation through epitaxy as the structure of urate and calcium oxalate crystals are rather similar. Another suggested mechanism is that urate acts as an anti-inhibitor of precipitation and growth of calcium oxalate crystals. 

In this reaction, the calcium ions and bicarbonate are combined in an aqueous medium to form calcium carbonate, which is slightly soluble in water. The calcium carbonate formation in surface waters and its precipitation into the oceanic floor is important in the transference of carbon from surface to deep water [49]. 

S. P. Wilson, F. Liu, R. E. Wilson and P. R. Housley Optimization of calcium phosphate transfection for bovine chromaffin cells relationship to calcium phosphate precipitate formation. Anal. Biochem., 226, 212-220 (1995). 

Crystallization of calciiun carbonate is highly dependent on precipitation conditions. In the classical method, much of the scientific investigation of calcium carbonate formation focused on the seed growth of anhydrous calcite crystals from solutions of low supersaturation [23-26]. A crystal can precipitate via epitaxy directly from the liquid solution so that the nuclei bear the same structure as the final crystal. 

Divalent cations (ions such as magnesium, calcium and barium can result in precipitate formation of polymers containing carboxylic acid groups. Polymers containing sulphonic acid groups are much less susceptible to this problem). 

Orazem et al. (1993, 1997) and Kennel-ley et al. (1993) took up this subject from the theoretical as well as the practical point of view, considering the cathodic protection of pipelines covered with insulation, characterized by leakiness (holidays and discrete holidays). Mathematical models have been created for different placements of anodes and their distance from the pipeline. In several papers, results are presented of theoretical calculations of the current and potential distribution and their comparison with experimental results. The finite element technique was used to solve the Laplace equation for potentials under boundary conditions, which describe the state of the insulation and the metal surface. Carson and Orazem (1998) also investigated the polarization characteristics of a pipeline as a function of time based on the formation of calcium precipitates. The results of these investigations were utilized in the construction of cathodic protection for the Trans-Alaska pipeline. More information on the CP of insulated pipelines is given in Sec. 8.4.4, while... 

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