Solubility potassium bitartrate

The bitartrate ion can combine with potassium ion, also present in high concentrations in grapes, to form the soluble salt potassium bitartrate (also known as cream of tartar). In water sodium bitartrate is fairly soluble 1 g dissolves in 162 ml of water at room temperatureJ1 In alcohol solution (formed as fermentation of the wine yields ethanol), the solubility of potassium bitartrate is significantly reduced 8820 ml of ethanol are required to dissolve 1 g of the saltJ As a consequence deposits of potassium bitartrate form as the salt precipitates out of solution. 

To prevent the formation of wine crystals during the bottling process, winemakers use a method known as cold stabilization. By lowering the temperature of the wine to 19-23°F for several days or weeks, the solubility of tartrate crystals is lowered, forcing the crystals to sediment. The resulting wine is then filtered off the tartrate deposit. The temperature dependence of the solubility of potassium bitartrate is readily apparent in the following comparison while 162 ml of water at room temperature dissolves 1 g of the salt, only 16 ml of water at 100°C are needed to solubilize the same amount of saltJ l Recent developments employ a technique known as electrodialysis to remove tartrate, bitartrate, and potassium ions from newly fermented wine at the winery before potassium bitartrate crystals form. 

Suppositories Sodium bicarbonate and potassium bitartrate in a water soluble polyethylene glycol base otc)... 

Figure 8-3 Solubility of potassium hydrogen tartrate increases when the salts MgS04 or NaCI are added. There is no effect when the neutral compound glucose is added. Addition of KCI decreases the solubility. (Why ) [From C. J. Marzzacco. "Effect of Salts and Nonelectrolytes on the Sdutxlity of Potassium Bitartrate." J. Chem. Ed. 1998. 75.1628.]... 

A white, crystalline powder, soluble in 1<)2 parts of cold, and in 20 parts of boiling, water, and insoluble in alcohol. Potassium bitartrate is also soluble in solutionis of sodium hydroxide and potassium carbonate, with the evolution of carbon dioxide. The preparation contains 100 per cent of... 

Tartaric Acid. Quantitative measures of total tartrate are useful in determining the amount of acid reduction required for high acid musts and in predicting the tartrate stability of finished wines. Three procedures may be used. Precipitation as calcium racemate is accurate (85), but the cost and unavailability of L-tartaric acid are prohibitive. Precipitation of tartaric acid as potassium bitartrate is the oldest procedure but is somewhat empirical because of the appreciable solubility of potassium bi-tartrate. Nevertheless, it is still an official AO AC method (3). The colorimetric metavanadate procedure is widely used (4, 6, 86, 87). Tanner and Sandoz (88) reported good correlation between their bitartrate procedure and Rebeleins rapid colorimetric method (87). Potentiometric titration in Me2CO after ion exchange was specific for tartaric acid (89). 

Bitartrate Stabilization. Potassium and tartaric acid are natural constituents of the grape. Wine content of these constituents depends on a number of variables, not all well understood variety, vintage, and weather pattern degree of skin contact alcohol level bitartrate holding capacity of phenolic compounds and potassium binding capacity of the wine (30, 35). Most wines after fermentation are supersaturated solutions of potassium bitartrate. This compound is less soluble at lower temperatures, and, thus, lower temperatures will cause precipitation of bitartrate crystals. This lowering of temperature and subsequent removal of crystals by filtration is called cold stabilization. 

Reduction of tartaric is, of course, incidental to fermentation wherever wine is made. This acid, mainly present in grapes as potassium bitartrate, is much more soluble in water (the principal ingredient of grape juice) than in alcoholic solutions. Thus, as grape juice ferments and alcoholic content... 

Part of the original fruit acids may be consumed by yeasts and, especially, bacteria (see malolactic fermentation ). On the other hand, yeasts and bacteria produce acids, e.g. succinic and lactic acids. Furthermore, acid salts become less soluble as a result of the increase in alcohol content. This is the case, in particular, of the monopotassium form of tartaric acid, which causes a decrease in total acidity on crystallization, as potassium bitartrate still has a carboxylic acid function. 

This convention is justified by its convenience, provided that (Section 1.4.2) there are no sudden inflection points in the neutralization curve of the must or wine at the pK of the organic acids present, as their buffer capacities overlap, at least partially. In addition to these somewhat theoretical considerations, there are also some more practical issues. An aqueous solution of sodium hydroxide is used to determine the titration curve of a must or wine, in order to measnre total acidity and buffer capacity. Sodium, rather than potassium, hydroxide is used as the sodium salts of tartaric acid are soluble, while potassium bitartrate would be likely to precipitate out during titration. It is, however, questionable to use the same aqueous sodium hydroxide solution, which is a dilute alcohol solution, for both must and wine. 

An increase in true acidity, i.e. a decrease in pH, may occur during bitartrate stabilization, in spite of the decrease in total acidity caused by this process. This may also occur when must and, in particular, wine is tartrated, due to the crystallization of potassium bitartrate, which becomes less soluble in the presence of alcohol. 

While potassium bitartrate is perfectly soluble in water, it is relatively insoluble in alcohol. Thus, in a dilute alcohol solution at 10% v/v and 20°C, its solubility (S) is only 2.9 g/1. 

Fig. 1.11. Determining the solubility (A) and hypersolubility (B) exponential curves of potassium bitartrate in a wine. Defining the hyper-saturation and instability fields according to the KTH content (Maujean et al, 1985). DS = saturation field 1, dissolved KTH 2, supersaturated, surfused KTH 3, crystallized KTH rcs , spontaneous crystallization temperature when 1.1 g/1 KTH is added rsat , saturation temperature of a wine in which 1.1 g/1 KTH have been dissolved...

Calcium tartrate is a relatively insoluble salt, ten times less soluble than potassium bitartrate (see... 

Stabilizing wines to prevent precipitation of calcium tartrate is not easy, as the crystallization of potassium bitartrate does not indnce that of calcium tartrate, despite the fact that these two salts should logically syncrystallize as they have the same crystal systems. On the contrary, crystallization of TCa may induce that of KTH. The prevention of calcium tartrate precipitation is further complicated by the fact that the solubility of TCa (Postel, 1983) is not very temperature-sensitive. Thns, TCa is hardly three times more soluble at 20°C than at —4°C. 

L-Tartaric acid is found in wines as the poorly soluble potassium hydrogen tartrate salt (potassium bitartrate) that often crystallises in young wines and when the wine is cooled as cream of tartar, known in winemakers jargon as tartrates. The crystals are harmless, but their presence is generally undesirable to consumers. The cream of tartar formation can be prevented by cold stabilisation of wines. 

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. 

Potassium compounds impart a violet color to a nonluminous flame if not masked by the presence of small quantities of sodium. In neutral, concentrated or moderately concentrated solutions of potassium salts, sodium bitartrate TS (10%) slowly produces a white, crystalline precipitate that is soluble in 6 N ammonium hydroxide and in solutions of alkali hydroxides or carbonates. The precipitation may be accelerated by stirring or mbbing the inside of the test tube with a glass rod or by the addition of a small amount of glacial acetic acid or alcohol. 

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