Precipitation of carbonate salts

Precipitation of Carbonate Salts. In the Appendix, equations are given for the calculated degrees of saturation of calcite, S3, and of dolomite, S4, based on regression of these properties at the conditions shown in Table III. Figure 7 shows the effects of pH and PCo2 for solutions that are saturated with calcite or dolomite. In each case the solutions are saturated with calcium sulfite and gypsum, and the content of sodium chloride is 200 mmoles/kg H20. 

Using an anion exchange membrane instead of a liquid caustic alkali electrolyte in an alkaline fuel cell allows avoids problems of leakage, carbonation, precipitation of carbonate salts, and gas electrode flooding, increasing the volumetric energy density. It appears that the anion exchange membrane fuel cells (AEMFCs) have the potential to succeed in portable applieations [92,93]. 

Additional phosphonic acid is derived from by-product streams. In the manufacture of acid chlorides from carboxyUc acids and PCl, phosphonic acid or pyrophosphonic acid is produced, frequentiy with copious quantities of yellow polymeric LOOP. Such mixtures slowly evolve phosphine, particularly on heating, and formerly were a disposal problem. However, purification of this cmde mixture affords commercial phosphonic acid. By-product acid is also derived from the precipitate of calcium salts in the manufacture of phosphinic acid. As a consequence of the treatments of the salt with sulfuric acid, carbonate is Hberated as CO2 and phosphonic acid goes into solution. 

The largest use of calcium hypochlorite is for water treatment. It is also used for I I and household disinfectants, cleaners, and mildewcides. Most of the household uses have been limited to in-tank toilet bowl cleaners. In areas where chlorine cannot be shipped or is otherwise unavailable, calcium hypochlorite is used to bleach textiles in commercial laundries and textile mills. It is usually first converted to sodium hypochlorite by mixing it with an aqueous solution of sodium carbonate and removing the precipitated calcium carbonate. Or, it can be dissolved in the presence of sufficient sodium tripolyphosphate to prevent the precipitation of calcium salts. However, calcium hypochlorite is not usually used to bleach laundry and textiles because of problems with insoluble inorganic calcium salts and precipitation of soaps and anionic detergents as their calcium salts. 

The degree of concentration that can be achieved by RO may be limited by the precipitation of soluble salts and the resultant scaling of membranes. The most troublesome precipitate is calcium sulfate. The addition of polyphosphates to the influent will inhibit calcium sulfate scale formation, however, and precipitation of many of the other salts, such as calcium carbonate, can be prevented by pretreating the feed either with acid or zeolite softeners, depending on the membrane material. 

The level of calcium in solution will depend upon the presence of precipitating anions, notably phosphate and carbonate. Calcium will precipitate as the phosphate to give hydroxyapatite, Caio(P04)6(OH)2, in bones and teeth, and as the phosphate or carbonate to give other structures, including small crystals, or non-crystalline deposits in cells. Small crystals of calcium carbonate, found in the inner ear of some animals, are responsible for the control of balance. Various calcified tissues result from the precipitation of calcium salts, such as hydroxyapatite in the calcification of the aortic wall, and the oxalate in various stones. 

B. (s)-(+)-S-Methoxymethylpyrrolidine. A solution of 180 g of potassium hydroxide in 720 mL of water is added to the crude product and the mixture is vigorously stirred under argon overnight. Saturation with potassium carbonate (500 g) causes precipitation of potassium salts, which are filtered off by suction (large Buchner funnel) and washed with ether. The filtrate is extracted with ether (3 x 300 mL) (Note 11) and the ether layer is acidified with 100 mL of 12 N hydrochloric acid under ice cooling in a hood (evolution of fumes) and extracted twice with 100 mL of water to yield an aqueous solution of the hydrochloride of 2-methoxymethylpyrrolidine (Note 12). 

Lead chromates and lead molybdates are produced by precipitation of soluble salts in aqueous media. Various lead sources include litharge, lead nitrate, basic lead actetate, and lead carbonate. The lead carbonate and basic lead acetate are used primarily to control particle size. Other ingredients include acids, alkalis, sodium bichromate, and sodium chromate. Additionally, molybdate orange manufacture involves the use of sodium molybdate and sodium sulfate as raw materials. 

The mixed precipitate of double salt and ferrous ferricyanide is filtered out, washed to remove sulphates and sulphocyanides and decomposed by boiling with sodium carbonate, forming the sodium ferrocyanide and setting free the ammonia which is distilled off and collected. The sodium ferrocyanide solution is filtered off from the iron-lime precipitate, concentrated and crystallized as already described on page 404. Unfortunately the double salt precipitate is very difficult to wash, with the result that frequently considerable amounts of sulphates pass into the finished liquor as sodium sulphate. The first crop of crystals is normally a pure, high-grade sodium ferrocyanide. The first mother liquor is concentrated to proper density and crystallized in like manner. 

In the carbonate. basic leaching process, both carbonate and bicarbonate ions are required to buffer the solution and prevent precipitation of uranium salts. In both acidic and basic leaching, complex anions are formed. The solutions may therefore be upgraded by anion exchange or anion solvant extraction (SX) processes. The upgraded solution is normally treated by selective precipitation of umaium by pH adjustment. 

While investigating the radiochemical properties of uranium, W. Crookes and Becquerel made an important discovery. Precipitating a carbonate salt from a solution containing uranyl ions, they discovered that while the uranium remained in the supernatant liquid in... 

As the salt is precipitated at once from carbon tetrachloride, its composition is dependent on the reaction temperature and the nature of the starting material, - because precipitation of the salt and interconversion leading to equilibration (72 5 73 74) occur con-... 

Baryta may be recognised, either in the free state, or in its salts, by its giving, with alkaline carbonates, a white precipitate of carbonate, and with sulphuric acid or any soluble sulphate, a white precipitate of sulphate of baryte. The latter is quite insoluble in Water and actds and hence baryta and its salts are much used as tests for snlphtrric acid. 

Formation of the scale nature of inorganic deposits is caused by precipitation of a salt from the water phase of the system. This form of deposit, called scale, is the most common form of inorganic deposits. There are several different types of scales found in the paper industry. Examples are calcium carbonate, calcium sulphate, barium sulphate, aluminium hydroxide and calcium oxalate. All these precipitates are formed because the water solubility of the respective ion pairs is exceeded. 

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