Precipitated solids calcium carbonate

The calcium levulate precipitate was separated from the reaction mixture by filtration and washed with cold water. The precipitate was suspended in water to give a thick slurry, and solid carbon dioxide added until the solution was colorless to phenolphthalein. A heavy precipitate of calcium carbonate was now present and free fructose remained in the solution. 

Oceanic surface water is everywhere supersaturated with respect to the two solid calcium carbonate species calcite and aragonite. Nevertheless carbonate precipitation is exclusively controlled by biological processes, specifically... 

Inside newiy formed caverns, calcium carbonate precipitates from water dripping from the ceilings of the chambers. This happens when water that is saturated with carbon dioxide and calcium hydrogen carbonate comes into contact with air. Some of the dissolved CO2 escapes into the gas phase. This shifts the two equilibria to the left, and solid calcium carbonate precipitates ... 

Bachra, B. N., Trautz, O., and Simon, S. L. Precipitation of calcium carbonates and phosphates. II. A precipitation diagram for the system calcium-carbonate-phosphate and the heterogeneous nucleation of solids in the metastability region. Adv. Arch. Fluorine Res. Dental Caries Prev. 3,101-118 (1965). 

If a small amount of an acid is added to some of the suspected carbonate (either solid or in solution) then effervescence occurs. If it is a carbonate then carbon dioxide gas is produced, which will turn limewater milky (a cloudy white precipitate of calcium carbonate forms, see Chapter 13, p. 215). 

The calcium levulate precipitate was separated from the reaction mixture by filtration and washed with cold water. The precipitate was suspended in water to give a thick slurry, and solid carbon dioxide added until the solution was colorless to phenolphthalein. A heavy precipitate of calcium carbonate was now present and free fructose remained in the solution. The calcium carbonate precipitate was removed by filtration, and the filtered solution was found to contain 1,436 g of fructose as determined by optical rotation. A small amount of calcium bicarbonate was present as an impurity in solution and was removed by the addition of oxalic acid solution until a test for both calcium and oxalic acid was negative. The insoluble calcium oxalate precipitate was removed by filtration. 

Equation 1.6 shows the precipitation of calcium carbonate, the quantity being calculated from the total calcium and dissolved calcium ions. For the sake of simplicity, it is considered as mol/dm3 units however, in reality, it is a separate solid phase. The chemical species of hydrocarbonate as a function of pH are shown in Figure 1.2. 

The most actively cycled reservoir of carbon is atmospheric C02 (it constitutes 0.034% of the atmosphere). Carbon dioxide dissolves readily in water and is in direct equilibrium with dissolved inorganic forms of carbon (H2C03, HCO, and CO7-, see Section 6.2.1.3). Once there, it may precipitate as solid calcium carbonate (limestone). Corals and algae encourage this reaction and build up limestone reefs in the process, but a much larger portion in the deep sea equilibrates only at the slow rate of... 

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. 

CaC03(r) + C02( ) + H20(/) Thus, in your hot water pipes, solid calcium carbonate precipitates from solution and collects as scale on the inside of the pipes. After we have discussed acid-base reactions in Chapter 5, it will be possible to explain how the plumber can remove this obstruction. 

For artefacts recovered from marine sites, they are often covered in concretions. These are hard layers of calcareous deposit derived from decaying shells of aquatic animals (e.g. barnacles, mussels, etc.) or hardness salts present in seawater. The latter is present as soluble bicarbonate ions (HC( )3 ) in sea or fresh water. At cathodic sites on the metal surface, there is a rise in the local pH due to the production of OH- during the reduction of dissolved oxygen gas (see Equation (10) in corrosion section). This results in the precipitation of solid calcium carbonate (CaC03) scale on the cathodic sites according to the following reaction ... 

Both calcium carbonate and ammonium sulphate are formed. The precipitate of calcium carbonate is filtered off and the solution of ammonium sulphate evaporated to obtain the solid salt. In the Merseburg plant in Germany, 2,300 tons of gypsum were being consumed daily in this operation in 1923, for the production of 2,000 tons daily of sulphate of ammonia. The gypsum is obtained from the company s own mines in the Harz Mountains, abort 60 miles southeast of the plant. 

Clarkson JR, Price TJ, Adams CJ (1992) Role of metastable phases in the spontaneous precipitation of calcium-carbonate. J Chem Soc Faraday Trans 88 243-249 Craig DQM (1990) Polyethyelene glycols and drug release. Drug Dev Ind Pharm 16 2501-2526 Craig DQM (2002) The mechanisms of drug release from solid dispersions in water-soluble polymers. Int J Pharm 231 131-144... 

Ilmewater A solution of calcium hydroxide that is used to test for the presence of carbon dioxide. If carbon dioxide is bubbled through limewater, a solid precipitate of calcium carbonate is formed. 

From a chemical point of view, carbonation is the reaction between calcium ions (Ca ) and carbonate ions (CCh ) in aqueous solution. This leads to the precipitation of a solid calcium carbonate phase, as described by the following reaction scheme ... 

Depending on several factors such as temperature, ion concentration and the presence of other ions in solution, a solid calcium carbonate phase precipitate (6). 

Heavy metals often can be removed effectively by chemical precipitation in the form of carbonates, hydroxides, or sulfides. Sodium carbonate, sodium bisulfite, sodium hydroxide, and calcium oxide are all used as precipitation agents. The solids precipitate as a floe containing a large amount of water in the structure. The precipitated solids need to be separated by thickening or filtration and recycled if possible. If recycling is not possible, then the solids are usually disposed of to a landfill. 

Conduct the preparation in the fume cupboard. Dissolve 250 g. of redistilled chloroacetic acid (Section 111,125) in 350 ml. of water contained in a 2 -5 litre round-bottomed flask. Warm the solution to about 50°, neutralise it by the cautious addition of 145 g. of anhydrous sodium carbonate in small portions cool the resulting solution to the laboratory temperature. Dissolve 150 g. of sodium cyanide powder (97-98 per cent. NaCN) in 375 ml. of water at 50-55°, cool to room temperature and add it to the sodium chloroacetate solution mix the solutions rapidly and cool in running water to prevent an appreciable rise in temperature. When all the sodium cyanide solution has been introduced, allow the temperature to rise when it reaches 95°, add 100 ml. of ice water and repeat the addition, if necessary, until the temperature no longer rises (1). Heat the solution on a water bath for an hour in order to complete the reaction. Cool the solution again to room temperature and slowly dis solve 120 g. of solid sodium hydroxide in it. Heat the solution on a water bath for 4 hours. Evolution of ammonia commences at 60-70° and becomes more vigorous as the temperature rises (2). Slowly add a solution of 300 g. of anhydrous calcium chloride in 900 ml. of water at 40° to the hot sodium malonate solution mix the solutions well after each addition. Allow the mixture to stand for 24 hours in order to convert the initial cheese-Uke precipitate of calcium malonate into a coarsely crystalline form. Decant the supernatant solution and wash the solid by decantation four times with 250 ml. portions of cold water. Filter at the pump. 

A) Preparation of 4-Acetyl-7-Chloro-1,2,3,4-Tetrahydro-1-Methyl-5H-1,4-Bemodiazepin-5-one A mixture of 68.5 g (0.37 mol) of 5-chloro-N-methylanthranilic acid, 51 g (0.51 mol) of calcium carbonate, 76 g (0.37 mol) of bromoethylamine hydrobromide and 2.5 liters of water was stirred and heated under reflux for 3 hours. A solution of 23.4 g (0.26 mol) of anhydrous oxalic acid in 250 ml of water was slowly added to the refluxing mixture. The precipitated calcium oxalate was filtered off, and the filtrate adjusted to pH 7 with concentrated ammonium hydroxide. The filtrate was then concentrated to dryness in vacuo and the residue heated on the steam bath with 400 ml of 6 N ethanolic hydrogen chloride until the residue was crystalline. Filtration gave 122 g of N-(aminoethyl)-5-chloro-N-methylanthranilic acid hydrochloride as a solid. 

NOTE It has been shown that in the absence of phosphate, carbonate conditioning can produce precipitated solids in a non-adherent and mobile form by adjusting the proportion of calcium, magnesium and silica to correspond with the relationship ... 

Common pollutants in a titanium dioxide plant include heavy metals, titanium dioxide, sulfur trioxide, sulfur dioxide, sodium sulfate, sulfuric acid, and unreacted iron. Most of the metals are removed by alkaline precipitation as metallic hydroxides, carbonates, and sulfides. The resulting solution is subjected to flotation, settling, filtration, and centrifugation to treat the wastewater to acceptable standards. In the sulfate process, the wastewater is sent to the treatment pond, where most of the heavy metals are precipitated. The precipitate is washed and filtered to produce pure gypsum crystals. All other streams of wastewater are treated in similar ponds with calcium sulfate before being neutralized with calcium carbonate in a reactor. The effluent from the reactor is sent to clarifiers and the solid in the underflow is filtered and concentrated. The clarifier overflow is mixed with other process wastewaters and is then neutralized before discharge. 

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