Solubility calcium carbonate

Equilibrium with precipitation. The previous example calculated carbonate speciation admitting unrestricted solubility of all species. Actually, it is easily verified that the calculated calcium and carbonate concentrations exceed calcium carbonate solubility as measured by the solubility product... 

Calcium carbonate solubility is also temperature and pressure dependent. Pressure is a 6r more important fector than temperature in influencing solubility. As illustrated in Table 15.1, a 20°C drop in temperature boosts solubility 4%, whereas the pressure increase associated with a 4-km increase in water depth increases solubility 200-fold. The large pressure effect arises from the susceptibility of the fully hydrated divalent Ca and CO ions to electrostriction. Calcite and aragonite are examples of minerals whose solubility increases with decreasing temperature. This unusual behavior is referred to as retrograde solubility. Because of the pressure and temperature effects, calcium carbonate is fer more soluble in the deep sea than in the surfece waters (See the online appendix on the companion website). 

During a Dissolution of Cholesterol Monohydrate in Glycochenodeoxycholate-Glycoursodeoxycholate-Lecithin Solutions and Calcium Carbonate Solubility in Their Solutions... 

A convenient method of interpreting water analysis for the purpose of determining the calcium carbonate solubility equilibrium conditions is embodied in the Langelier equation. The Langelier equation can be used to... 

A derived expression relating to the saturation point of calcium carbonate solubility in water. Used frequently to interpret water analysis in order to determine the potential for CaCC>3 supersaturation and deposition (scaling) and also by inference, but not always correctly, the opposite nonscaling potential (corrosion risk). Although LSI is scaleless, the industry generally accepts and promotes the following ... 

Hi) pytkowicz, R. M., Disteche, A., and Disteche, S. Calcium carbonate solubility in seawater at in situ pressures. Earth. Plan. Sci. Letters 2, 430-432 (1967). 

Considering pressure, a threshold value is found above which the amount of dissolved C02 and (bi)carbonate, together with the dissolved calcium (determined also by L/S ratio) exceeds the calcium carbonate solubility product, such that precipitation can occur. 

Carbonate alkalinity is not a directly analyzable quantity, but it can be derived from the titration alkalinity (A ) by a relationship which is temperature and pressure dependent. pH is also variable with pressure and temperature. In addition, pH can be defined several ways depending on which buffer system is used, whether liquid junction potentials are considered, and what definition of ionic strength is used. The values of the apparent dissociation constants and calcium carbonate solubility constants are dependent on exactly what definition of seawater pH is used and what standardization technique is used (15, 16, 17). 

Calculation of Apparent Calcium Carbonate Solubility Products The precise determination of the solubility of calcite... 

The Change in Apparent Calcium Carbonate Solubility Constants with Temperature (After Horse et al. (35))... 

Calcium Carbonate Solubility in Open and Closed Systems... 

Salinger, Y., Y. Geifman, and M. Aronowich. 1993. Orthophosphate and calcium carbonate solubilities in the Upper Jordan watershed basin. J. Environ. Qual. 22 672-677. 

The next approach to scale control was reduction of potential calcium carbonate by acidification of makeup water. Sulfuric acid is added to reduce alkalinity and convert most of the calcium bicarbonate to calcium sulfate. Calcium sulfate is soluble up to about 1,700 parts per million in cooling waters at ordinary temperatures, whereas calcium carbonate solubility is less than 30 ppm. So by slightly acidifying makeup water we greatly reduce tendency for calcium carbonate deposition. The calcium sulfate level in concentrated cooling water is controlled by bleed-off adjustment—manually or automatically. 

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