Водорода пероксид

Описание

Hydrogen peroxide (H2O2) is a strong oxidizing agent that is used extensively in industry and medicine. It is usually available as aqueous solutions in concentrations of 3, 30 or 90 percent by weight. The 3 percent solution is used as a topical antiseptic and cleansing agent, and as a constituent in mouthwashes, dentifrices and sanitary lotions; the 30 percent as an effective bleaching agent and for other industrial uses; and the 90 percent as a vigorous oxidizer of rocket fuels. The anhydrous form is a colorless, bittertasting liquid with an ozone-like odor. In the absence of stabilizing agents (e.g., phosphates, tin), hydrogen peroxide solutions are unstable and decompose upon standing, agitation, exposure to light, or heating. Hydrogen peroxide reacts vigorously with many oxidizing as well as reducing agents. Concentrated solutions are highly caustic to the skin. In addition to its effectiveness as a bleach, hydrogen peroxide has proved to be a useful antimicrobial agent. This latter property has been utilized in some countries as a preservative of milk and whey.

Химические свойства

Colorless liquid; pure compound or 90% solution unstable; bitter taste; density 1.463 g/mL; boils at 150.2°C; freezes at –0.43°C; vapor pressure 9.9 torr at 50°C and 121.5 torr at 100°C; viscosity 1.245 centipoise at 20°C; surface tension 80.4 dyn/cm at 20°C; miscible with water in all proportions; soluble in ether; densities of 30%, 70%, and 90% H2O2 solutions are 1.1081, 1.2839 and 1.3867 g/mL, respectively, at 25°C; freezing points at these concentrations are –25.7°C, –40.3°C and –11.5°C, respectively; and their boiling points are 106.2°C, 125.5°C and 141.3°C, respectively; decomposed by many organic solvents; pKa at 25°C is 11.62.

Физические свойства

Colorless liquid; pure compound or 90% solution unstable; bitter taste; den-sity 1.463 g/mL; boils at 150.2°C; freezes at -0.43°C; vapor pressure 9.9 torrat 50°C and 121.5 torr at 100°C; viscosity 1.245 centipoise at 20°C; surfacetension 80.4 dyn/cm at 20°C; miscible with water in all proportions; soluble inether; densities of 30%, 70%, and 90% H₂O₂solutions are 1.1081, 1.2839 and1.3867 g/mL, respectively, at 25°C; freezing points at these concentrations are-25.7°C, -40.3°C and -11.5°C, respectively; and their boiling points are106.2°C, 125.5°C and 141.3°C, respectively; decomposed by many organic sol-vents; pKaat 25°C is 11.62.

История

Hydrogen peroxide was prepared first by Thenard in 1818. It has many industrial applications. Aqueous solutions at varying concentrations are used for bleaching fabrics, silks, furs, feathers and hair; as a dough conditioner; and a bleaching and oxidizing agent in foods; for cleaning metals; as a laboratory reagent for oxidation; as an antiseptic; in sewage and wastewater treatment; and in preparation of inorganic and organic peroxides. An 80% concentrated solution is used in rocket propulsion.

Использование

hydrogen peroxide is a bleaching and oxidizing agent, detergent, and antiseptic. It is generally recognized as a safe preservative, germ killer, and skin bleacher in cosmetics. If used undiluted, it can cause burns of the skin and mucous membranes.

Определение

hydrogen peroxide: A colourlessor pale blue viscous unstable liquid,H₂O₂; r.d. 1.44; m.p. –0.41°C; b.p.150.2°C. As with water, there is considerablehydrogen bonding in theliquid, which has a high dielectricconstant. It can be made in the laboratoryby adding dilute acid to bariumperoxide at 0°C. Large quantitiesare made commercially by electrolysisof KHSO₄.H₂SO₄ solutions. Anotherindustrial process involvescatalytic oxidation (using nickel, palladium,or platinum with an anthraquinone)of hydrogen and waterin the presence of oxygen. Hydrogenperoxide readily decomposes in lightor in the presence of metal ions togive water and oxygen. It is usuallysupplied in solutions designated byvolume strength. For example, 20-volume hydrogen peroxide wouldyield 20 volumes of oxygen per volumeof solution. Although the peroxidesare formally salts of H2O2, thecompound is essentially neutral.Thus, the acidity constant of the ionizationH₂O₂ + H₂O ?H₃O⁺ + HO_2–is 1.5 × 10^-12 mol dm^-3. It is a strongoxidizing agent, hence its use as amild antiseptic and as a bleachingagent for cloth, hair, etc. It has alsobeen used as an oxidant in rocketfuels.

Методы производства

From 1920 to 1950, the primary method of production was electrolysis. One process involved passing electric current through sulfuric acid to produce the peroxydisulfate ion (S2O8 2-), which was then hydrolyzed to H2O2: 2H₂O + S₂O₈^2- (aq) 2H₂SO₄^-(aq) + H₂O₂(aq).the relatively high cost of electricity of this method encouraged a search for a more economical production process. Hydrogen peroxide is currently produced on a large scale using the anthraquinone autooxidation procedure, which was developed in the 1940s. In this process, an anthraquinone, typically 2-ethyl-anthraquinone, is hydrogenated to a hydroquinone (2-ethyl-anthrahydroquinone) then reoxidized back to the anthraquinone (2-ethyl-anthraquinone) while forming hydrogen peroxide . A metal palladium or nickel catalyst is used to convert the anthraquinone to the hydroquinone, followed by autooxidation in air to generate hydrogen peroxide. The anthraquinone and hydrogen peroxide are separated; the former is recycled to repeat the process while the hydrogen peroxide is purified.

Реакции

Hydrogen peroxide reacts with many compounds, such as borates, carbonates, pyrophosphates, sulfates, silicates, and a variety of organic carboxylic acids, esters, and anhydrides to give peroxy compounds or peroxyhydrates. A number of these compounds are stable solids that hydrolyze readily to give hydrogen peroxide in solution.

Общее описание

A colorless liquid dissolved in water. Vapors may irritate the eyes and mucous membranes. May violently decompose on contact with most common metals and their compounds. Contact with combustible material may result in spontaneous ignition. Corrosive to tissue. Under exposure to fire or heat containers may violently rupture due to decomposition. Used to bleach textiles and wood pulp, in chemical manufacturing, food processing, and in water purification.

Реакции воздуха и воды

Water soluble.

Профиль реактивности

The hazards associated with the use of HYDROGEN PEROXIDE(especially highly concentrated solutions) are well documented. There is a release of enough energy during the catalytic decomposition of 65% peroxide to evaporate all water and ignite nearby combustible materials. Most cellulose materials contain enough catalyst to cause spontaneous ignition with 90% peroxide. Contamination of concentrated peroxide causes the possibility of explosion. Readily oxidizable materials, or alkaline substances containing heavy metals may react violently. Solvents(acetone, ethanol, glycerol) will detonate on mixture with peroxide of over 30% concentration, the violence increasing with concentration. Concentrated peroxide may decompose violently in contact with iron, copper, chromium, and most other metals or their salts, and dust(which frequently contain rust). During concentration under vacuum of aqueous or of aqueous-alcoholic solutions of hydrogen peroxide, violent explosions occurred when the concentration was sufficiently high(>90%), [Bretherick 2nd ed., 1979]. Hydrogen selenide and hydrogen peroxide undergo a very rapid decomposition, [Mellor 1:941(1946-1947)].

Опасность

Hydrogen peroxide is a strong oxidizing agent. Concentrated solutions, even a 30% aqueous solution, should be handled carefully. The compound decomposes violently in the presence of trace impurities. Inhibitors are, therefore, added at trace levels to prevent decomposition. Explosion can occur when concentrated solutions are heated or brought in contact with a number of organic substances that are readily oxidizable or that form organic peroxides, such as alcohols, aldehydes, ketones, anhydrides, and carboxylic acids (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd ed. New York: John Wiley & Sons). Also, reactions with metals, metal alloys, a number of metal salts and oxides, and concentrated mineral acids can proceed to explosive violence.

Угроза здоровью

Contact with aqueous concentrations of less than 50% cause skin irritation, but more concentrated solutions of H202 are corrosive to the skin. At greater than 10% concentration, hydrogen peroxide is corrosive to the eyes and can cause severe irreversible damage and possibly blindness. Hydrogen peroxide is moderately toxic by ingestion and slightly toxic by inhalation. This substance is not considered to have adequate warning properties. Hydrogen peroxide has not been found to be carcinogenic in humans. Repeated inhalation exposures produced nasal discharge, bleached hair, and respiratory tract congestion, with some deaths occurring in rats and mice exposed to concentrations greater than 67 ppm

Пожароопасность

Hydrogen peroxide is not flammable, but concentrated solutions may undergo violent decomposition in the presence of trace impurities or upon heating

Воспламеняемость и взрывоопасность

Hydrogen peroxide is not flammable, but concentrated solutions may undergo violent decomposition in the presence of trace impurities or upon heating.

Контактные аллергены

Hydrogen peroxide is an oxidizing agent used as a topi- cal antiseptic, and as part of permanent hair-dyes and color-removing preparations, and as a neutralizing agent in permanent waving. The concentration of the hydrogen peroxyde solution is expressed in volume or percentage: Ten volumes correspond to 3%. It is an irritant.

Токсикология

Hydrogen peroxide is used as an agent to reduce the number of bacteria in dairy products or other foodstuffs. In the dairy industry, hydrogen peroxide also has been used as a substitute for heat pasteurization in the treatment of milk and as a direct preservative in keeping the quality of the milk. In Japan, it has been used as a preservative for fish-paste products. Hydrogen peroxide also has a bleaching effect. The use of highly pure hydrogen peroxide in manufactured cheese has been approved by the United States Food and Drug Administration (industrial grade hydrogen peroxide is usually a 3–35% aqueous solution; a commercial home product is a 3% aqueous solution).
Acute toxicities (LD50) of hydrogen peroxide for rats are 700 mg/kg/b.w. and 21 mg/kg/b.w. by subcutaneous injection and intravenous injection, respectively. When large amounts of hydrogen peroxide were injected directly into the stomachs of rats, weight and blood protein concentrations were changed slightly. When hydrogen peroxide was mixed with feed, however, no abnormalities were observed. The use of bactericides has been limited due to their toxicity to humans, and only hydrogen peroxide currently is recognized for use.

Канцерогенность

Chronic studies in mice found adenomas and carcinomas of the duodenum after oral administration. The IARC has determined that there is limited evidence in experimental animals for the carcinogenicity of hydrogen peroxide and inadequate evidence in humans.

хранилище

Use extreme care when carrying out reactions with hydrogen peroxide because of the fire and explosion potential (immediate or delayed). The use of safety shields is advisable, and is essential for experiments involving concentrated (>50%) solutions of hydrogen peroxide. Sealed containers of hydrogen peroxide can build up dangerous pressures of oxygen, owing to slow decomposition.

Методы очистки

The 30% material has been steam distilled using distilled water. Gross and Taylor [J Am Chem Soc 72 2075 1950] made 90% H2O2 approximately 0.001M in NaOH and then distilled it under its own vapour pressure, keeping the temperature below 40o, the receiver being cooled with a Dry-ice/isopropyl alcohol slush. The 98% material has been rendered anhydrous by repeated fractional crystallisation in all-quartz vessels. EXPLOSIVE IN CONTACT WITH ORGANIC MATERIAL.

Несовместимости

Contact with many organic compounds can lead to immediate fires or violent explosions (consult Bretherick for references and examples). Hydrogen peroxide reacts with certain organic functional groups (ethers, acetals, etc.) to form peroxides, which may explode upon concentration. Reaction with acetone generates explosive cyclic dimeric and trimeric peroxides. Explosions may also occur on exposure of hydrogen peroxide to metals such as sodium, potassium, magnesium, copper, iron, and nickel.

Утилизация отходов

Excess hydrogen peroxide and waste material containing this substance should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines. For more information on disposal procedures, see Chapter 7 of this volume.