Solubilities of Inorganic Citrates in Water

As mentioned above, physical properties of aqueous solutions of inorganic citrates were systematically investigated only in few cases. These are aqueous solutions of neutral and acidic sodium and potassium citrates and diammonium hydrogen citrate. Mostly, the volumetric and compressibility properties are reported, and they are based on measured densities and speed velocities. In deahng with a particular physical property, all available citrates are considered together. 

Consideringimportanceofcalciumcitrates(Ca3(Cit)2 4H20andCa3(Cit)2 6H2O) in citric acid production, milk products and in medical procedures [134], its 

Difficulty to measure very low solubilities is clearly iUustrated in the case of dissolution of calcium citrate at 25 °C in pure water (Fig. 5.1). The scattering of experimental solubilities for more soluble magnesium and iron citrates is less pronounced (Fig. 5.2). From similar investigations, it is worthwhile to mention also the Bolton [138] detailed solubility study in systems included tiisodiumcitrate, acetylsalicyUc acid (aspirin) and benzoic acid. 

Solubility products of Mg, Ca, Zn, Cd, Hg and Th citrates and those of the rare earth element citrates (La Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er and Y) in 0.1 M (H, Na) CIO4 solutions were reported at 25 °C by the Skornik group [139-146] (Table 5.3). They also determined solubilities of some rare earth citrates in HCl and KOH solutions and found that these solubihties are larger than those in pure water and increase with 

In most reported solubility determinations, the soUd phase compositions in equilibrium with saturated solutions were not established. And therefore, they are uncertain with regard to transition temperamres of different hydrates. Thus, in the investigated temperature range, solubilities presented in Tables 5.2 and 5.3 describe not only thermodynamically stable but probably also metastable states. 

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Table 5.2 Solubility of inorganic citrates in water as a function of temperature... 

Solubilities of Inorganic Citrates in Water Table 5.4 (continued)... 

CS forms water-soluble salts with inorganic and organic acids including glyoxylate, pyruvate, tartarate, malate, malonate, citrate, acetate, lactate, glycolate and ascorbate. Natural CS showed more solubility in organic acids when the pH of the solution was less than 6.5. Facile water-miscible salts of CS are formed by neutralisation with acids such as lactic, hydrochloric, acetic or formic. 

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