Precipitate, aluminium hydroxide solubility

Aluminates are for the most part crystalline, soluble compounds, obtained by the action of metallic oxids or hydroxids upon alumina. Potassium aluminate, KaAlaOa-fSAq, is formed by dissolving recently precipitated aluminium hydroxid in potash solution. It forms white crystals very soluble in HaO, insoluble in alcohol caustic and alkaline. By a large quantity of HaO it is decomposed into aluminium hydroxid, and a more alkaline salt, KgAltOa. 

Aqueous ammonia can also behave as a weak base giving hydroxide ions in solution. However, addition of aqueous ammonia to a solution of a cation which normally forms an insoluble hydroxide may not always precipitate the latter, because (a) the ammonia may form a complex ammine with the cation and (b) because the concentration of hydroxide ions available in aqueous ammonia may be insufficient to exceed the solubility product of the cation hydroxide. Effects (a) and (b) may operate simultaneously. The hydroxyl ion concentration of aqueous ammonia can be further reduced by the addition of ammonium chloride hence this mixture can be used to precipitate the hydroxides of, for example, aluminium and chrom-ium(III) but not nickel(II) or cobalt(II). 

Historically, lakes refered to the first type of synthetic organic pigments made from water soluble dyes by precipitation onto alumina hydrate (aluminium hydroxide). 

Ammonium solution white gelatinous precipitate of aluminium hydroxide, Al(OH)3, slightly soluble in excess of the reagent. The solubility is decreased in the presence of ammonium salts owing to the common ion effect (Section 1.27). 

The precipitation of aluminium hydroxide by solutions of sodium hydroxide and ammonia does not take place in the presence of tartaric acid, citric acid, sulphosalicylic acid, malic acid, sugars, and other organic hydroxy compounds, because of the formation of soluble complex salts. These organic substances must therefore be decomposed by gentle ignition or by evaporating with concentrated sulphuric or nitric acid before aluminium can be precipitated in the ordinary course of qualitative analysis. 

Ammonia or ammonium sulphide solution white precipitate of beryllium hydroxide, Be(OH)2, similar in appearance to aluminium hydroxide, insoluble in excess of the reagent, but readily soluble in dilute hydrochloric acid, forming a colourless solution. Precipitation is prevented by tartrates and citrates. 

Sodium hydroxide solution white gelatinous precipitate of beryllium hydroxide, readily soluble in excess of the precipitant, forming tetrahydroxo-beryllate ion, [Be(OH)4]2 on boiling the latter solution (best when largely diluted), beryllium hydroxide is reprecipitated (distinction from aluminium). The precipitate is also soluble in 10 per cent sodium hydrogen carbonate solution (distinction from aluminium). 

Lake colours are made by precipitating a water soluble colour with an aluminium, calcium or magnesium salt on to aluminium hydroxide. The dye content can be varied from 10 to 40%. The particle size of the finished product must be small enough to give a speck-free but economical coverage. 

Abundant yellow or white salt crusts are present on waste rock and at the surface of the soil. The crusts comprise alum-like sulfate minerals containing variable amounts of sodium, potassium, iron and aluminium, such as the mineral jarosite. They are often very soluble in water, releasing acid and precipitating ferric hydroxides. 

Aluminium and Precipitator Ash. In some Victorian brown coals significant quantities of acid-soluble aluminium are found. This is believed to be present as aluminium hydroxide which is dispersed throughout the water phase of the coal. During combustion of this coal, the refractory aluminium oxide formed takes the shape of the relics of the plant material present in the coal, thus forming an extremely low density ash (approximately 100 kg/m ). Whilst the collection of these particles by electrostatic precipitation is possible, the problem of reentrainment on rapping has necessitated the use of larger sized units than would otherwise be required. It is therefore important to determine the acid soluble aluminium fraction in the coal to determine if precipitation of fly ash is likely to be a problem. 

However, while oxidization may not change, interaction with the media may yield more soluble forms. A sparingly soluble metal compound can be considered as one for which a solubility product can be calculated, and which will yield a small amount of the available form by dissolution. However, it should be recognized that the final solution concentration may be influenced by a number of factors, including the solubility product of some metal compounds precipitated during the transformation/dissolution test, e.g. aluminium hydroxide. 

Hp + 3Na,C03 + Al3(SOJ3 2A1(0H)3 + 3Na,SO + 3CO, + H,0 as an assistant floculant. If additional alkali is not added, the total alkalinity is reduced and part of aluminium sulphate, being water soluble may pass through the filter. As aluminium hydroxide and metals precipitate downwards, clear water arrives at the top and is decanted. 

Alumina was synthesized from precipitated gel of aluminium hydroxide which was extruded to cylindrical pellets and activated under controlled conditions to yield high surface area. Chromia was loaded on alumina by soaking alumina in soluble chromates salts and activated in muffle furnace at about 600 C (4 to 10)... 

Aluminium. Ammonium chloride and ammonium hydroxide give a white precipitate of aluminium hydroxide, insoluble in excess soluble in sodium hydroxide. 

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 cooled product is ground and extracted with water. The soluble sodium aluminate is removed as a filtrate from the dicalcium silicate and insoluble matter. Injection of carbon dioxide into the filtrate produces a precipitate of aluminium hydroxide and sodium carbonate liquor (11.10), which is recycled to the initial stage. The aluminium hydroxide is heated to above 300 °C to produce pure alumina which is dissolved in fused cryolite (NaAIp4) at about 900 °C and electrolysed between carbon electrodes to produce molten aluminium. 

Fluoride can be precipitated by lime as the calcium salt. At pH 10, the residual level is in the range 10 to 20 mg/1 (as F) [28.2]. The precipitate should be removed by adsorption on magnesium hydroxide, calcium phosphate, or activated alumina, but not on aluminium hydroxide, as alum and aluminate form a soluble complex with fluoride. 

Formation of the scale nature of inorganic deposits is caused by precipitation of a salt from the water phase of the system. This form of deposit, called scale, is the most common form of inorganic deposits. There are several different types of scales found in the paper industry. Examples are calcium carbonate, calcium sulphate, barium sulphate, aluminium hydroxide and calcium oxalate. All these precipitates are formed because the water solubility of the respective ion pairs is exceeded. 

Discovery.—In 1797 L. N. Vauquelin undertook to prove the chemical identity of the emerald and beryl, -which had already been suspected by Haiiy, and in the course of his analytical research, discovered that a portion of the precipitate which had previously been supposed to be aluminium hydroxide, was thrown out of its solution in potassium hydroxide on boiling. He also found that this new hydroxide was soluble in ammonium carbonate, formed no alum and was in many ways different from aluminum. These observations led him to announce in a paper read before the Institute on Peb. 14, 1898 (1798 i), the discovery of a new earth. ... 

Uneertain. One suggestion is that magnesium sulfate changes ferrous sulfate into less easily absorbed salts, or increases its polymerisation. Carbonates possibly cause the formation of poorly soluble iron complexes. Aluminium hydroxide is believed to precipitate iron as the hydroxide and ferrie ions can become intercalated into the aluminium hydroxide crystal lattice, leaving less available for absorption. 

Von Weimarn experimented mainly on the formation of precipitates of slightly insoluble inorganic compounds like silver sulphate, barium sulphate, aluminium hydroxide, which he prepared by double decomposition of other salts, added together under varying conditions of concentration and temperature and with or without addition of other liquids, like alkohol, to influence solubility and medium conditions. The essential result of his experiments may be cast into the form of the following equation ... 

---