Precipitation carbonate system

The entire system is operated at high temperatures to increase the solubility of potassium carbonate. Therefore, the designer must be careful to avoid dead spots in the system where the solution could cool and precipitate solids. If solids do precipitate, the system may suffer from plugging, erosion, or foaming. 

Another source of divergence is the use of different models for the aqueous carbonate systems. Precipitation and dissolution experiments can be carried out in closed or open systems and various ways of pH-adjustments (see 8.2). 

Epithermal ore deposits are hydrothermal deposits that form at shallow crustal levels. A wide spectrum of ore deposits of a different nature occurs in this category. Typical temperatures of mineralization range from 150 to 350°C with variable salinities. Individnal deposits often reveal that more than one type of fluid was involved in the formation of a single ore deposit. One of the fluids involved often appears to be of meteoric origin. In many deposits different fluids were alternatively discharged into the vein system and promoted the precipitation of a specific suite of minerals, snch as one fluid precipitating snlfides and another precipitating carbonates (Ohmoto 1986). 

NHj and CO2 and precipitates a high-purity, basic beryllium carbonate. If the aqueous system has the stoichiometry of (NtL Be COi) , analogous to the ammonium nranyl carbonate system, the basic beryllium carbonate product of hydrolysis is 2BeCC>3 Be(OH)2- This compound is readily dissolved in all mineral acids, making it a valuable starting material for laboratory synthesis of beryllium salts of high purity. 

Several areas of research seem to merit top priority attempt to verify published stability constants of environmental interest at lower metal concentrations and higher pH determine stability constants that are not currently known, the prime example being the plutonium-carbonate system assess the interplay of complexation, hydrolysis, and polymerization at environmental pH values, as these factors are important but not well understood under neutral conditions study the complex chemistry of plutonyl(V), which some workers believe to be an important species in ground waters attempt to elucidate the nature and behavior of polymeric species with the ultimate objective of developing quantitative, reproducible expressions for dispersion, precipitation. 

Formaldehyde-water solution. Mix 50 ml of 38% formaldehyde with 50 ml of distd w in a 400-ml beaker, add 4 drops of 1% phenolphthalein or thymolphthalein indicator (0.8g per 100ml ethanol) and neutralize with carbonate-free 0.5N NaOH soln dropwise to a pink color (pH 8.6) on glass-calomel electrode system Standard sodium hydroxide, 0.5N. Dissolve 20g of carbonate-free NaOH in 500ml CO2-free water, add enough Ba chloride to more than 2 liters distd w to precipitate carbonate present, let the Ba carbonate settle, and filter into a 1 liter volumetric flask. Standardize the NaOH soln by adding it. from a buret into a soln of 2 g of potassium acid phthalate (weighed accurat ely on an analytical balance), and four drops of phenolphthalein indicator in 75—100ml COa-free water contained in a 150-ml beaker until the first appearance of a pink end point... 

In order to understand the formation of beachrock, some fundamentals of the marine carbonate system (C02-H20-CaC03) and calcium carbonate precipitation and dissolution have to be considered. Only limited aspects of the subject can be discussed here as the topic is complex and treated at length in various textbooks (e.g. Lippmann, 1973 Berner, 1980 Morse and Mackenzie, 1990). 

In cases where is present to influence the carbonate system by the dissolution/ precipitation reaction of calcite ... 

As proton sources, organic acids are likely to have an important influence on a variety of pH dependent reactions, especially between 80 and 120 C. Geochemical models predict that addition of typical amounts of acetic acid to calcite saturated solutions at 100 C, can increase calcite solubility by several times. Organic acid anions also have an appreciable impact on the alkalinity and pH buffering capacity of formation waters. However, in most formation waters it is unlikely that calcite precipitation will result from simply increasing the pC02 of calcite-saturated solutions, unless pH is buffered by systems other than the acetate and carbonate systems. 

In many ground-water investigations, more data are collected than the minimum required to describe the carbonate system. Measurements of dissolved CO2 concentrations are often made as part of the suite of analyses for all dissolved gases or by base titrations in the field. Measurements of total dissolved carbonate concentrations made by precipitation of solid carbonate or evolution of CO2 following acidification may also be available. With such redundant analytical data, the internal consistency of all the carbonate data can be tested. 

Certain losses of CO from the sample into the inert atmosphere of the glove box, and due to that, an increase of pH and a precipitation of calcite seem to be inevitable. Only the combined in situ measurement of pH, CO and Ca + will lead to a reliable measurement of the calcite-carbonate-system. 

First, let us examine homogeneous (no precipitates), open systems. In these systems the carbonate species in solution are in equilibrium with the CO2 gas in the atmosphere above the solution. The normal atmosphere contains 10 - atm of CO2, and when this is in equilibrium with C02(a<,) from Eqs. 4-103 and 4-110, we obtain... 

The distribution of copper species in a natural water buffered by the carbonate system is presented in Fig. 5-5. The diagram is based on the presence of the copper precipitate tenorite, CuOjgj, If the solution were not in equilibrium with this solid, the species distribution would not be quite the same however, radical changes would not occur. Therefore, the diagram can be used to determine regions where certain species are important. From Fig, 5-5 it can be seen that only at below pH 6.5 is free... 

Travertine 1) Any finely crystalline massive concretionary limestone formed by surface or groundwater evaporation. 2) Any flowstone deposit, hence the usage travertine implying stalagmitic flowstone. 3) Any carbonate deposit formed within a cave or karst system by secondary precipitation. 4) Massive, hard, dense carbonate deposits formed in association with open-air springs, streams, lakes, or marshes that precipitate carbonate. 

Chlorhexidine is mainly used as an active ingredient in disinfectants, deodorants and antiseptics and as a preservative in cosmetics and pharmaceuticals. The EC positive list of preservatives permitted for use in cosmetics mentions Chlorhexidine and its salts with a maximum authorized concentration of 0-3%. Formulating and using the active ingredient one has to remember its cationic nature which causes reduction of activity in the presence of organic matter, e.g. blood, serum, soaps and other anionic compounds. Another cause of activity loss is based on the very low water-solubility of certain Chlorhexidine salts borate, citrate, carbonate, bicarbonate, chloride or phosphate salts precipitate in systems containing such anions. 

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