Calcium tartrate

Calcium tartrate is produced by extracting wine lees (deposited on the bottom of vats containing 19 to 38 % of potassium bitartrate) and grape marc (the residue from pressing grapes), filtering the solution and then adding slaked lime and calcium chloride [31.18]. 

The calcium tartrate is removed by filtration and treated with dilute sulfuric acid to produce a solution of tartaric acid and a precipitate of calcium sulfate. The tartaric acid is then concentrated by evaporation under reduced pressure and separated by crystallisation. Tartaric acid is widely used in the food and drink industries, in pharmaceutical preparations, as a retarding agent in plaster and gypsum formulations, and in the polishing and cleaning of metals. Food grade slaked lime is generally specified (e.g., [31.30] and Table 31.2). 

The Bayer process for the production of alumina uses caustie soda to extraet aluminium oxide from bauxite. The resulting solution of sodium aluminate also contains dissolved sodium silicate. The silicate is normally removed by allowing the aluminate and silicate to react to form precipitates of the zeolite structure having a eomposition of approximately NagAl6Si6024(0H)2. Slaked lime is added, when very low levels of silicate are required, to precipitate the silicate as cancrinite, which is removed, prior to the formation of the zeolite structures [31.19]. 

Slaked lime is also added to the sodium aluminate liquor to control carbonate levels by eausticising sodium earbonate (31.16). It also helps to control the level of phosphates by precipitating hydroxyapatite (31.17) — phosphates can interfere with the subsequent precipitation of aluminium hydroxide. 

The causticisation of soda ash by slaked lime is also used to generate the caustic soda required for the bauxite extraction when the price of lime relative to that of caustic soda justifies the additional handling and disposal costs. 

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The chemical reactions involved in tartaric acid production are formation of calcium tartrate from cmde potassium acid tartrate. 

Fig. 4. Manufacturing process for (R-R, R -tartaric acid (TA) and its salts, calcium tartrate (CT) and potassium tartrate (PT).

The acid potassium or calcium tartrates are found in many plants but the chief source of tartaric acid is the impuie acid potassium salt, which separates out as wine-lees, or argol from grape-juice in process of fermentation. 

Add calcium chloride and stir with a glass rod. A crystalline precipitate of calcium tartrate, C.,H40(,Cad-4H20, is formed u hich dissolves in acetic acid and caustic alkalis. Repeat the fniegoing test, but add a few drojts of acetic acid before the calcium chloride. There is no precipitate. Calcium sulphate also gives no precipitate with tartaric acid or neutial tartrates, ( compare reactions for OKalic acid, p. 100). 

O. Katsuki et al, KogyoKayaku 31(3), 131-7(1970) CA 78, 6073(1973) (Combustion preventive chemicals for coal mine expls. I. Organic compds. Out of 60 compds tested only ammonium, sodiym or potassium oxalate, sodium or potassium formate, and calcium tartrate were effective)... 

Additional Exercises Crystals of silver sulfate, silver chromate, calcium tartrate, and copper tartrate. 

Newly fermented wines are usually supersaturated with potassium bitartrate. Wineries routinely remove the excess potassium bitartrate in wines by refrigeration or ion exchange procedures. These steps are necessary to obtain a wine free of tartrate deposits after bottling. Calcium may also combine with tartrates which contribute to the deposits in wines. Generally, the stabilization practices for potassium bitartrate are sufficient to remove calcium tartrate from wines. 

In addition to deposits of crystalline potassium bitartrate, infrequent calcium tartrate deposits occur in wines. The calcium level of carefully produced wines is seldom high enough to cause stability problems. Occasionally, however, wines may extract calcium from improperly prepared filter materials. Prolonged storage in uncoated concrete tanks also will release calcium into wine. 

L-Calcium tartrate = 250 mg/liter Racemic calcium tartrate = 30 mg/liter... 

Cambitzi, A., The Formation of Calcium Tartrate in Wines, Analyst... 

Calcium. Excess calcium can occur in wines stored in concrete tanks or otherwise exposed to calcium (filter aids, calcium bentonite, etc.). After fortified wines are bottled, calcium tartrate may slowly precipitate. 

Calcium Tartrate. CaCjHjCV HiO, white solid, solubility at 0°C 0.0875. al 80°C 0.l8l)g anhydrous sail in I(XI ml saturated solulion, formed by reaction of calcium carbonate or hydroxide and tartaric acid, or by precipitation of Ca- with a tartrate solulion. 

Manufacture. The chemical reactions involved in tartaric acid production are formation of calcium tartrate from crude potassium acid tartrate, formation of tartaric acid from calcium tartrate, formation of Rochelle salt from argols. and formation of cream of tartar front tartaric acid and Rtxhelle salt (RS) liquors... 

It can precipitate as potassium hydrogen tartrate (KHT) or as calcium tartrate (CaT), the latter being practically insoluble in aqueous solutions. Their equilibrium solubility varies with temperature, pH, and alcohol content, while the presence of a few wine components, such as polysaccharides and mannoproteins, may hinder spontaneous nucleation even if the solution is supersaturated. From Figure 14 that shows the equilibrium tartaric acid-dissociated fractions versus pH and ethanol volumetric fraction (Berta, 1993 Usseglio-Tomasset and Bosia, 1978), it can be seen that in the typical pH range (3 4) of wines KHT is predominant. As temperature is reduced from 20 to 0°C, KHT solubility in water or in a 12% (v/v) hydro-alcoholic solution reduces from 5.11 to 2.45 kg/m3 or from 2.75 to 1.1 kg/m3, respectively (Berta, 1993). Each of these data also varies with pH and reaches a minimum at the pH value associated with the maximum concentration of the hydrogen tartrate anions. For the above-mentioned solutions, the solubility minimum shifts from pH 3.57 to pH 3.73 as the ethanol content increases from 0 to 12% (v/v) (Berta, 1993). 

White precipitate of calcium tartrate soluble in dilute acetic acid, dilute mineral acids, and in cold alkali solutions White precipitate, the reaction is ... 

Another method of acid amelioration, used to avoid water amelioration, is the addition of calcium salts for the purpose of substituting calcium for potassium ions. The resulting calcium bitartrate salts, being less soluble, increase the precipitation of bitartrate. This raises technical problems, one being that if the malo-lactic fermentation should take place subsequently, the wine may contain insufficient acidity of any kind. Another is that calcium tartrate precipitates slowly and in more finely divided form, often causing persistent hazes that are hard to remove. Often, too, this precipitation is delayed, leading to the presumption that the wine is tartrate stable. Only after it is bottled, the brilliant and supposedly stable wine may develop a delayed calcium tartrate haze and even a deposit. The calcium salt method in a refined form is used considerably in Germany but rarely here. 

L-Tartaric acid is an abundant constituent of many fruits such as grapes and bananas and exhibits a slightly astringent and refreshing sour taste. It is one of the main acids found in wine. It is added to other foods to give a sour taste and is normally used with other acids such as citric acid and malic acid as an additive in soft drinks, candies, and so on. It is produced by acid hydrolysis of calcium tartrate, which is prepared from potassium tartrate obtained as a by-product during wine production. Optically active tartaric acid is used for the chiral resolution of amines and also as an asymmetric catalyst. 

A. CALCIUM TARTRATE CRYSTALS GROWN BY THE STANDARD TECHNIQUE... 

Calcium tartrate is the easiest of all gel-growth experiments and yields the best results of all materials.1 2 Thus it has been the most used system for gel-growth studies, including nucleation, aging, and pH studies. 

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