Алюминий сернокислый

Химические свойства

Aluminum sulfate is a white powder, often used in water solution. The solution is a strong acid

Физические свойства

White powder; refractive index 1.47; density 2.71 g/cm³; mp 770°C (decomposes); hygroscopic; readily soluble in water (31% at 0°C; solubility increases with temperature 98% in boiling water); soluble in dilute mineral acids; slightly soluble in alcohol.

Вхождение

It occurs in nature in minerals; alunite, KAl₃(SO₄)₂(OH)₆and natroalunite, NaAl₃(SO₄)₂(OH)₆. The anhydrous salt is used in food applications.

Использование

Aluminum sulfate acts as a flocculating agent in the purification of drinking water, and in waste water treatment plants. It acts as a mordant in dyeing, printing, textiles and also used in paper manufacturing. It is a waterproofing agent and accelerator in concrete. Further, it is used as a foaming agent in fire fighting foam, photographic film and in photochemicals. It is also used in styptic pencils, pain relief and in dentistry for gingival retraction cords.

Подготовка

The anhydrous salt may be obtained by slow and progressive heating of commercial hydrated salt, Al₂(SO₄)₃ ?18H₂O. Most water molecules are lost at heating between 250 to 420°C. The last three water molecules are lost between 250 to 420°C at a heating rate of 10°C/min.

Определение

ChEBI: An aluminium sulfate that contains no water of crystallisation.

Общее описание

Anhydrous aluminum sulfate is a white crystalline solid. Aluminum sulfate is also obtained as an 18-hydrate Al2(SO4)3.18H2O. Both forms are soluble in water, noncombustible, and nontoxic. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. Aluminium sulfate is used in paper making, in firefighting foams, and in sewage treatment and water purification.

Реакции воздуха и воды

Dissolves in water with evolution of some heat. creates acidic solutions.

Профиль реактивности

Aqueous solutions of ALUMINUM SULFATE are acidic. The solid may corrode metals in presence of moisture.

Угроза здоровью

Inhalation of dust irritates nose and mouth. Ingestion of large doses causes gastric irritation, nausea, vomiting, and purging. Dust irritates eyes and skin.

Сельскохозяйственное использование

Alunogenite is a naturally occurring form of hydrated aluminum sulphate Al₂(SO₄)₃18 H₂O.

Промышленное использование

Aluminum chloride (AlCl₃) can be obtained by reacting carbon dioxide and chlorine with kaolin at high temperatures. It is highly hygroscopic with a specific gravity of 2.3. It is highly soluble in water and in organic solvents. Similar to aluminum sulfate, aluminum chloride is used as a co-depressant for calcite, fluorite and dolomite.

Профиль безопасности

Moderately toxic by ingestion and intraperitoneal routes. Experimental reproductive effects. Human mutation data reported. Hydrolyzes to form sulfuric acid, whch irritates tissue, especially lungs. When heated to decomposition it emits toxic fumes of SOx,.

Возможный контакт

Widely used in the paper industry, in waste and water treatment and treating sewage; in antiperspirants, deodorants; in flame-retardants; in tanning leather, sizing paper; mordant in dyeing, purifying water, waterproofing cloth, clarifying oils and fats; in agricultural pesticides; manufacturing aluminum salts and others

Перевозки

UN3264 Corrosive liquid, acidic, inorganic, n.o.s., Hazard class: 8; Labels: 8-Corrosive material, Technical Name Required. UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required

Методы очистки

It crystallises from hot dilute H2SO4 (l mL/g) on cooling in ice. When a solution of alumina (Al2O3) in conc H2SO4 is slowly cooled, Al2SO4 17 or 18H2O deposits as a crystalline mass. Al2SO4 17H2O is the stable form in equilibrium with its saturated aqueous solution at 25o [Smith J Am Chem Soc 64 41 1942]. This is purified by dissolving it in a small volume of H2O and adding EtOH until the sulfate readily crystallises from the oily supersaturated solution. It forms Al2O3 16H2O between 0-112o. On gradual heating, the hydrate melts, giving the anhydrous salt at ca 250o. Several hydrates up to 27H2O have been described. Further heating to red heat (~ 600-800o) causes decomposition to Al2O3 + SO3 + SO2 and O2 [Cobb J Soc Chem Ind 29 250 1910]. The ACS reagent is Al2O3 18H2O (98+%).

Несовместимости

In aqueous solution, aluminum sulfate forms sulfuric acid; reacts with bases and many other substances. Corrodes metals, some plastics and body tissues, especially in the presence of moisture.

Утилизация отходов

Pretreatment involves hydrolysis followed by neutralization with NaOH. The insoluble aluminum hydroxide formed is removed by filtration and can be heated to decomposition to yield alumina which has valuable industrial applications. The neutral solution of sodium sulfate can be discharged into sewers and waterways as long as its concentration is below the recommended provisional limit of 250 mg/L