Solubility hydrated compounds

Iron(III) ammonium citrate [1185-57-5] is of indefinite stoichiometry. A brown hydrated compound [1332-98-5] of iron(III) ammonium citrate contains 16.5—18.5% iron, - 9% ammonia, and 65% citric acid. A green hydrated compound [1333-00-2] contains 14.5—16% iron, 1% ammonia, and 75% citric acid. Iron ammonium citrates are water soluble but are insoluble in alcohol. The compounds are used to fortify bread, milk, and other foods (see... 

Binary Compounds. The fluorides of indium are IrF [23370-59-4] IrF [37501-24-9] the tetrameric pentafluoride (IiF ) [14568-19-5], and JIrFg [7789-75-7]. Chlorides of indium include IrCl, which exists in anhydrous [10025-83-9] a- and p-forms, and as a soluble hydrate [14996-61-3], and IrCl [10025-97-5], Other haUdes include IrBr [10049-24-8], which is insoluble, and the soluble tetrahydrate IrBr -4H20 IrBr [7789-64-2]-, and Irl [7790-41-2], Iridium forms indium dioxide [12030-49-8], a poorly characteri2ed sesquioxide, 11203 [1312-46-5]-, and the hydroxides, Ir(OH)3 [54968-01-3] and Ir(OH) [25141-14-4], Other binary iridium compounds include the sulfides, IrS [12136-40-2], F2S3 [12136-42-4], IrS2 [12030-51 -2], and IrS3 [12030-52-3], as well as various selenides and teUurides. 

Although there is no space to develop a detailed discussion of the solubilities of compounds of the transition elements, the general insolubility of their + 2 and + 3 hydroxides is important. The rationale underlying their insolubility can be summarized (i) the hydroxide ion is relatively small (152 pm ionic radius) and the ions of the +2 and +3 transition metals assume a similar size if their radii are increased by 60-80 pm, and (ii) the enthalpy of hydration of the hydroxide ion (—519 kJ mol ) is sufficiently negative to represent a reasonable degree of competition with the metal ions for the available water molecules, thus preventing the metal ions from becoming fully hydrated. Such effects combine to allow the lattice enthalpies of the hydroxides to become dominant. 

For example, sucrose molecules have a number of sites that can form a hydrogen bond with water to replace the attraction between the sucrose molecules. (See Figure 8.11.) The sucrose molecules separate and become hydrated, just like dissolved ions. The molecules remain neutral, however. As a result, sucrose and other soluble covalent compounds do not conduct electricity when dissolved in water. They are non-electrolytes. 

Chloral.—Chloral, or tri-chlor acet-aldehyde, was first prepared by Liebig in 1832 by the chlorination of alcohol as above. It may also be obtained by the direct action of chlorine upon acet-aldehyde. It is an oily liquid with a sweet suffocating odor. It boils at 97.7°. It does not mix with water but on boiling with water it forms a hydrated compound which crystallizes in large clear crystals, readily soluble in water. This is known as chloral hydrate. The structure of chloral hydrate is probably that of an addition product, viz., a, chlorinated di-hydroxy alcohol. In this compound we have an exception to the general rule that two hydroxyl groups can not be linked to the same carbon atom. 

The sodium salt is a white powder, little soluble in pure water, but solubilized in the presence of lithium ions. The solutions are unstable, and conversion to the [a2 P2Wi706,] ° anion is complete after several hours. In molar acetic acid-lithium acetate buffer the half-wave potentials (V vs SCE) are — 0.52 (4e) and —0,78 (2e). The PNMR spectrum of a freshly prepared solution in molar acetic acid-lithium acetate buffer exhibits two equal resonances at -l-O.l and —13.3 ppm (85% H3PO4 reference). In the IR spectrum the P—O bands are at 1130, 1075, and 1008 cm(KBr pellet). As occurs with hydrated compounds, some bands are shifted if the measurements are performed in mineral oil (1130, 1086, and 1009 cm " ). 

Added to this mix of molecular chemistries are the water-soluble salts, such as sulfates and chlorides, that likely form salt hydrate compounds and eutectic intergrowths with water ice. These salts are probably leached out from the accreted rocky components of primitive rocky solids that make up chondritic meteorites that rain down on Earth. ... 

Of the aluminium compounds with low solubility, hydrated aluminium oxide (usually called aluminium hydroxide with a non-stoichiometric structure) is of particular interest in hydrochemistry and the technology of water, and it is present mainly in the colloidal form. The structure A1(0H)3 corresponds only to the compound formed by precipitation of aluminium solutions by introducing carbon dioxide. At a higher temperature during precipitation with ammonia, aluminium oxide-hydroxide AIO(OH) can also be formed. When removing phosphates from water aluminium phosphate plays an important role it is stable in weakly acid media but is hydrolysed to A1(0H)3 in alkaline media. 

The phase diagram also illustrates a general practice concerning hydrate solubility. The solubility of compounds that form hydrates... 

RHODIUM (soluble compounds, as Rh)(Soluble rhodium compounds have variable molecular formulas and variable formula weights, depending upon the specific compound. The physical and chemical properties of one specific compound, for example, hydrate rhodium trichloride, are provided. The molecular formula for this substance is Cl3Rh-xH20. The molecular weight is reported as being greater than 209.)... 

SYNONYMS Synonyms vary depending upon the specific soluble rhodium compound, (hydrated rhodium trichloride) rhodium chloride, soluble rhodium trichloride. 

PHYSICAL PROPERTIES Physical appearance and odor vary depending upon the specific soluble rhodium compound, (hydrated rhodium trichloride) deep-red, hygroscopic crystals odorless solid or liquid very soluble in water soluble in hot ethanol MP (100°C, 212°F) (decomposes) BP (800°C, l472°F)(sublimes) DN/SG (>1) VD (NA) VP (<0.1 mmHg at 20°C). 

CHEMICAL PROPERTIES Chemical properties, reactivities, and incompatibilities vary depending upon the specific soluble rhodium compound, (hydrated rhodium chloride) rhodium chloride readily forms double salts with alkali chlorides some decomposition may occur at temperatures above 100°C (212°F) no incompatibilities have been reported FP (NA) LFL/UFL (NA) AT (NA) HC (NA). 

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