Hydroxides solubilities

Addition of alkali gives a green gelatinous precipitate of chromium(III) hydroxide, soluble in a large excess of strong alkali. 

Nickel was first isolated in 1751, and a relatively pure metal was prepared in 1804. In nature, nickel is found primarily as oxide and sulfide ores (USPHS 1977). It has high electrical and thermal conductivities and is resistant to corrosion at environmental temperatures between -20°C and +30°C (Chau and Kulikovsky-Cordeiro 1995). Nickel, also known as carbonyl nickel powder or C.I. No. 77775, has a CAS number of 7440-02-0. Metallic nickel is a hard, lustrous, silvery white metal with a specific gravity of 8.9, a melting point of about 1455°C, and a boiling point at about 2732°C. It is insoluble in water and ammonium hydroxide, soluble in dilute nitric acid or aqua regia, and slightly soluble in hydrochloric and sulfuric acid. Nickel has an atomic weight of 58.71. Nickel is... 

The OH concentration increases (decreases) by one order of magnitude for every unit increase (decrease) in pH. This means that the formation of a metal hydroxide (whether as a colloid or as a precipitate) in aqueous solution will be strongly dependent on temperature when the product of the free metal ions and OH ions is close to the hydroxide solubility product, although increase in Ksp with temperature may partially offset this effect. 

NIOBIC ACID. Any hydrated form of Nb Os. It forms as a white, insoluble precipitate when a potassium hydrogen sulfate fusion of a niobium compound is leached with hot water or when niobium fluoride solutions are treated widi ammonium hydroxide. Soluble in concentrated sulfuric acid, concentrated hydrochloric acid, hydrogen fluoride, and bases. Important in analytical determination of niobium. See also Niobium. 

White precipitate of aluminum hydroxide soluble in excess sodium hydroxide... 

White precipitate of zinc hydroxide soluble in excess ammonia... 

Inevitably, corrosion is not a process that proceeds by straightforward, uncomplicated active dissolution, especially over extended exposure periods. Reactive materials (e.g., Fe, carbon steel, Cu, U02) corroding in neutral to slightly alkaline solutions (4 < pH < 9) when oxide/hydroxide solubilities are low, tend to accumulate corrosion product deposits. 

Kuma K, Nishioka J, Katsuhiko M (1996) Controls on iron(ni) hydroxide solubility in seawater the influence of pH and natural organic chelators. Limnol Oceanogr 41 396 107... 

Kuma K, Katsumoto A, Kawakami H, Takatori F, Matsunaga K (1998) Spatial variability of Fe(in) hydroxide solubility in the water column of the northern North Pacific Ocean. Deep-Sea Res Part I 45 91-113... 

Explain why calcium hydroxide (solubility 0.165 g per 100 g water at 20°C) is much more soluble than magnesium hydroxide (solubility 0.0009 g per 100 g water at 20°C). 

When a salt is introduced to water (e.g., A1C13s), the charged metal (Al3+) has a strong tendency to react with H20 or OH" and forms various Al-hydroxy species. Metal-hydroxide reactions in solution exert two types of influences on metal-hydroxide solubility, depending on the quantity of hydroxyl supplied. They either decrease or increase metal solubility. The solubility of a particular metal-hydroxide mineral depends on its Ksp, quantity of available hydroxyl, and solution pH of zero net charge. For example, aluminum (Al3+) forms a number of hydroxy species in water as shown below ... 

Commonly, different metals exhibit different solution pH of zero net charge. For this reason, different metals exhibit minimum solubility at different pH values, which makes it difficult to precipitate effectively two or more metals, as metal-hydroxides, simultaneously. Thus metal-hydroxide solubility as a function of pH displays a U-shaped behavior. The lowest point in the U-shaped figure signifies the solution pH of zero net charge and is demonstrated below. Consider the solid Fe(OH)2s,... 

Since pH = 14 - pOH" (where pOH" denotes the negative log of OH"), the pH of minimum solubility for Fe(OH)2s would be 11.21. The example above is only for demonstration purposes since only two of the many potentially forming Fe2+-hydroxy species were employed. A graphical representation of the solubility of Fe(OH)2s (Eq. 2.47) and Fe(OH)3s as a function of pH are shown in Figure 2.7. The data in Figure 2.9 show the solubility of various heavy metals as a function of pH, whereas the data in Figure 2.10 show the decrease in metal-hydroxide solubility as pH increases (common ion effect). They do not, however, show the expected increase in metal-hydroxide solubility as pH increases. 

Minimum metal-hydroxide solubility or metal solubility at the solution pH of zero net charge can be approximated using the K of the metal-hydroxide pair with zero charge (M(OH)° Consider,... 

One may plot Equations 2.69, 2.71, and 2.73 as pAlhydroxy species versus pH. This will produce three linear plots with different slopes. Equation 2.69 will produce a plot with slope 3, whereas Equations 2.71 and 2.73 will produce plots with slopes 2 and -1, respectively. The sum of all three aluminum species as a function of pH would give total dissolved aluminum. This is demonstrated in Figure 2.12, which describes the pH behavior of eight Al-hydroxy species. The following three points can be made based on Figure 2.12 (1) aluminum-hydroxide solubility exhibits a U-shaped behavior, (2) aluminum in solution never becomes zero, and (3) different aluminum species Predominate at different pH values. 

Metal-Hydroxides. Most heavy metals may precipitate via strong bases (e.g., NaOH and KOH) as metal-hydroxides [M(OH)n]. These precipitation reactions are described in Chapter 2. As noted, metal-hydroxide solubility exhibits U-shape behavior and ideally its lowest solubility point in the pH range allowed by law (e.g., pH 6-9) should be lower than the maximum contaminant level (MCL). However, not all heavy metal-hydroxides meet this condition. The data in Figure 12.1 show the various metal-hydroxide species in solution when in equilibrium with metal-hydroxide solid(s). In the case of Pb2+, its MCL is met in the pH range of 7.4-12, whereas the MCL of cadmium (Cd) the MCL is not met at any pH. Similar information is given by the solubility diagrams of Cu2+, Ni2+, Fe3+ and Al3+. 

The solubility of metal-hydroxide precipitates in water varies depending on ionic strength and number of pairs and/or complexes (Chapter 2). A practical approach to determining the pH of minimum metal-hydroxide solubility, in simple or complex solutions, is potentiometric titration, as demonstrated in Figure 12.3. The data show that potentiometric titration of a solution with a given heavy metal is represented by a sigmoidal plot. The long pH plateau represents pH values at which metals precipitate the equivalence point, or titration end point, indicates the pH at the lowest metal-... 

The substance is insoluble in water and in dilute mineral acids, but dissolves in oxalic acid, yielding a blue solution at one time largely used for ink. When dried, the salt contains 9-10 molecules of water, and if heated strongly m air it bums, leaving a residue of ferric oxide. Alkalies decompose it, precipitating ferric hydroxide, soluble ferrocyanides passing into solution —... 

TAPPI Standard T212 os-76, One Per Cent Sodium Hydroxide Solubility of Wood and Pulp ... 

Benzyltriethylammonium chloride functions as a phase-transfer catalyst. The chloride is soluble in the basic aqueous phase and is converted into bcnzyltricthyl-ammonium hydroxide, soluble in the organic phase. The hydroxide ion reacts with chloroform to give dichlorocarbene with regeneration of benzyltriethylammonium chloride. 

Kuma K., Katsumoto A., Nishioka J., and Matsunaga K. (1998b) Size-fractionated iron concentrations and Fe(III) hydroxide solubilities in various coastal waters. Estuar. Coast. Shelf Set 47, 275-283. 

Baes and Mesmer (1976) provide a critical evaluation of the extensive information on the identity of metal-ion species and their hydrolysis products in solutions, as well as the solid oxides and hydroxides they produce. They provide a critical compilation of hydrolysis equilibrium and oxide and hydroxide solubility constants. 

Melting point melts above 220°C, with decomposition. Solubility soluble in solutions of alkali hydroxides soluble 1 in 500 of water. 

The data for TUB hydroxide solubility in different media have recently receive a great deal of attention due to their importance for development of clean-up technologies, etc. It is known that the Pu(OH)3 solubility in water and 5M ammonium solution is equal to 7.5 10 M and 3.8 10 " M, respectively [12]. The solubility product of the Pu(III) hydroxide is about 2 10 ° [13,14]. According to the data of different authors, the solubility products of Pu(OH)3 and Am(OH)3 hydroxides are equal to about 10 [15]. The solubility of Pu(III) hydroxide in 5M NH4OH is 3.8 10"" M [16], and the solubility of Am(III) in 0.01-5M NH4OH is 1.6 10" M [17]. The suggested chemical form of these alkali-dissolved hydroxides is a neutral Am(OH)3-type molecule, which does not tend to have an amphoteric nature or to form complexes with OH" ions. Despite the low solubility of TUE(III) hydroxides, in the crystalline form they can be easily dissolved. Thus, the concentration of the Am(OH)3 and Cm(OH)3 colloid solutions may exceed more than 100 g/L [4]. 

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