Гидроксид натрия химические свойства, назначение, производство
Химические свойства
Sodium hydroxide, NaOH,also referred to as caustic soda or sodium hydrate(and formerly known as lye), is a white,massive, deliquescent crystalline solid that is soluble in water,alcohol, and glycerol. It melts at 318°C (606 OF) and is the most widely used and available alkaline chemical. Most sodium hydroxide is produced as a coproduct of chlorine through the use of electrolytic cells;the cells are of the diaphragm, mercury, or membrane type. Some sodium hydroxide is marked as produced in the cells;most is evaporated and sold as 50% and 73% solutions or as anhydrous beads. Most caustic end uses require solutions of relatively low concentrations. Caustic soda is used as an analytical reagent and chemical intermediate, in scouring and cleaning baths,in rubber reclaiming and petroleum refining, in quenching baths for heat treating of steel,in cutting and soluble oils,in soaps and detergents, and in a wide variety of other applications.
Физические свойства
White orthorhombic crystals, produced in the form of pellets, lumps, sticks, beads, chips, flakes or solutions; hygroscopic; very corrosive; rapidly absorbs CO2 and water from the air; density 2.13 g/cm3; melts at 323°C; vaporizes at 1388°C; vapor pressure 1 torr at 739°C and 5 torr at 843°C; very soluble in water (110 g/100mL at room temperature), generating heat on dissolution; aqueous solutions highly alkaline, pH of 0.5% solution about 13 and 0.05% solution about 12; soluble in methanol, ethanol and glycerol (23.8 g/100 mL methanol and 13.9 g/100 mL ethanol at ambient temperatures.).
Использование
Sodium hydroxide is one of the most important industrial chemicals. In volume, it is in the top ten chemicals produced in the United States. It is used in manufacturing a large number of compounds including several sodium salts, in treating cellulose for producing rayon and cellophane, and in manufacturing soaps, detergents, pulp, and paper. Sodium hydroxide is a common neutralizing agent for acids in acid-base titrations and petroleum refining. Another major application is extracting metals from their ores where alkali fusion, such as fusion with caustic soda, often is applied to open the ores. Additionally, sodium hydroxide is used to precipitate metals as hydroxides. Other uses are in reclaiming rubber, dissolving casein in plastics production, refining vegetable oils, processing textiles, as an eluant in ion chromatography, etching and electroplating, and as a laboratory reagent. Sodium hydroxide also is used as a strong base in many organic synthesis and base-catalyzed reactions.
Определение
The most important commercial
caustic.
Методы производства
Sodium hydroxide is manufactured by electrolysis of brine using
inert electrodes. Chlorine is evolved as a gas at the anode and
hydrogen is evolved as a gas at the cathode. The removal of chloride
and hydrogen ions leaves sodium and hydroxide ions in solution.
The solution is dried to produce the solid sodium hydroxide.
A second method uses the Kellner–Solvay cell. Saturated sodium
chloride solution is electrolyzed between a carbon anode and a
flowing mercury cathode. In this case the sodium is produced at the
cathode rather than the hydrogen because of the readiness of
sodium to dissolve in the mercury. The sodium–mercury amalgam is
then exposed to water and a sodium hydroxide solution is
produced.
Реакции
Общее описание
A white solid. Corrosive to metals and tissue. Used in chemical manufacturing, petroleum refining, cleaning compounds, drain cleaners.
Реакции воздуха и воды
Soluble in water. Dissolution can liberate enough heat to cause steaming and spattering and ignite adjacent combustible material [Haz. Chem. Data 1966].
Опасность
Corrosive to tissue in presence of mois-
ture, strong irritant to tissue (eyes, skin, mucous
membranes, and upper respiratory tract), poison by
ingestion.
Угроза здоровью
Sodium hydroxide is a highly corrosive substancethat causes damage to human tissues.Its action on the skin is somewhat differentfrom acid burns. There is no immediate pain,but it penetrates the skin. It does not coagulateprotein to prevent its further penetration,and thus the caustic burn can become severeand slow healing. Spilling of its concentratedsolutions into the eyes can result in severeirritation or permanent injury.
It is toxic by ingestion as well as inhalationof its dust. Although the oral toxicity ofa 5–10% solution of caustic soda was foundto be low in test animals, high dosages atgreater concentrations can cause vomiting,prostration, and collapse. The oral lethal dosein rabbits is 500 mg/kg (NIOSH 1986).
Sodium hydroxide dusts or aerosols areirritating to the eyes, nose, and throat. Prolongedexposure to high concentrations in airmay produce ulceration of the nasal passage.
Пожароопасность
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.
Воспламеняемость и взрывоопасность
Sodium hydroxide and potassium hydroxide are not flammable as solids or aqueous
solutions.
Фармацевтические приложения
Sodium hydroxide is widely used in pharmaceutical formulations to
adjust the pH of solutions. It can also be used to react with weak
acids to form salts.
Промышленное использование
Caustic soda (NaOH) is regarded as the strongest alkaline pH regulator. Caustic soda
is a very active substance and is highly corrosive. The bulk of caustic soda is manufactured
by electrolysis of saturated brines (NaCl). Caustic soda has a very strong pHregulating
capability (i.e. from pH 7 to pH 14) at a relatively low dosage compared to
other alkaline substances. Commercially, caustic soda is available in anhydrous form,
but in most mining applications the caustic soda is supplied as a 50% solution.
In the mineral processing industry, sodium hydroxide is mostly used for alkalinity control
during the processing of non-metallic minerals. In base metal flotation, the use of
sodium hydroxide is rare.
Профиль безопасности
Poison by intraperitoneal route. Moderately toxic by ingestion. Mutation data reported. A corrosive irritant to skin, eyes, and mucous membranes. When heated to decomposition it emits toxic fumes of NanO.
Безопасность
Sodium hydroxide is widely used in the pharmaceutical and food
industries and is generally regarded as a nontoxic material at low
concentrations. At high concentrations it is a corrosive irritant to
the skin, eyes, and mucous membranes.
LD50 (mouse, IP): 0.04 g/kg
LD50 (rabbit, oral): 0.5 g/kg
Возможный контакт
NaOH is utilized to neutralize acids and make sodium salts in petroleum refining, viscose rayon; cellophane, plastic production; and in the reclamation of solutions of their salts. It is used in the manufacture of mercerized cotton, paper, explosives, and dyestuffs in metal cleaning; electrolytic extraction of zinc; tin plating; oxide coating; laundering, bleaching, dishwashing; and it is used in the chemical industries.
Описание
Гидроксид натрия представляет собой основание, состоящее из двух частей, соединённых ионной связью: щелочного активного металла натрия – Na и гидроксильной группировки – OH.
Чистое вещество имеет вид твёрдых гранул сферообразной формы либо мелких мыльных чешуек белого цвета. Запах отсутствует, вкус напоминает мыло, разъедающий, горький.
Химические свойства
Белое твёрдое веществон.у.. Хорошо растворяется в воде с выделением тепла.
Концентрированные растворы опасны, при попадании на кожу оставляют ожоги, отсюда и название «едкий натр».
При кристаллизации из водных растворов при н.у. выделяется в виде кристаллогидрата NaOH·H2O.
Безводный гидроксид натрия очень гигроскопичен, на воздухе «расплывается», активно поглощая пары воды и углекислый газ (образуются кристаллогидрат и карбонат).
Применение
В наше время широко используется в разных отраслях жизнедеятельности, в том числе медицине, фармакологии, пищевой индустрии. В сельском хозяйстве, например, каустическую соду используют для проверки коровьего молока на наличие примесей.
В косметологии едкий натр добавляют в шампуни, мыло, жидкости для снятия лака, кремы, а также в средства для избавления от ороговевшей кожи. Кроме того, гидроксид натрия – незаменимое вещество в нефтеперерабатывающей, целлюлозно-бумажной промышленности и в производстве дизельного топлива.
Производство
Химический метод – термическое разложение соды до оксида натрия, углекислого газа и воды, оксид натрия далее с водой дает гидроксид.
Электрохимический метод (основной) – электролиз хлорида натрия.
хранилище
Sodium hydroxide should be stored in an airtight nonmetallic
container in a cool, dry place. When exposed to air, sodium
hydroxide rapidly absorbs moisture and liquefies, but subsequently
becomes solid again owing to absorption of carbon dioxide and
formation of sodium carbonate.
Перевозки
UN1823 NaOH, solid, Hazard class: 8; Labels: 8-Corrosive material. UN1824 NaOH, solution, Hazard class: 8; Labels: 8-Corrosive material
Несовместимости
Sodium hydroxide is a strong base and is incompatible with any
compound that readily undergoes hydrolysis or oxidation. It will
react with acids, esters, and ethers, especially in aqueous solution.
Утилизация отходов
Discharge into tank containing water, neutralize, then flush to sewer with water.
Регуляторный статус
GRAS listed. Accepted for use as a food additive in Europe.
Included in the FDA Inactive Ingredients Database (dental
preparations; injections; inhalations; nasal, ophthalmic, oral, otic,
rectal, topical, and vaginal preparations). Included in nonparenteral
and parenteral medicines licensed in the UK. Included in the
Canadian List of Acceptable Non-medicinal Ingredients.
Гидроксид натрия препаратная продукция и сырье
сырьё
препарат