МЫШЬЯК химические свойства, назначение, производство
Описание
Arsenic is a metalloid of the nitrogen group. Two allotrope forms of elemental arsenic have been reported:
yellow arsenic and grey arsenic, the latter being usually the more stable form. Arsenic readily oxidises in
air to arsenic trioxide (As2O3). Arsenic is mostly found either in its native state or as arsenic sulfide in the
form of realgar (As4S4) or orpiment (As2S3). Arsenic can exist in three different valence states (zerovalent,
trivalent and pentavalent). Arsenic forms covalent bonds with carbon, oxygen and hydrogen. The toxicity
varies widely and depends on the physical state of the compound and its absorption/elimination rate.
Trivalent arsenics (As(III)) are derivatives of the arsenous acid (H2AsO3-arsenite) and arsenic trioxide
(AsO3). Examples of pentavalent arsenic (As(V)) include derivatives of the arsenic acid (H3AsO4 -arsenate).
Organic arsenic-based compounds, that is, compounds containing arsenic-carbon bonds, are usually less
toxic than their inorganic counterparts. This is mainly due to their quicker excretion from the human body.
Arsenic is known to be one of the most toxic heavy metals. Compounds containing arsenic have a long
history of use as poisons, but they also have a long historical medicinal use.
Химические свойства
Arsenic (As) is the third element in Group VA of the periodic table. Elemental arsenic can be found in two solid forms: yellow and gray or metallic, with specific gravities of 1.97 and 5.73, respectively (CRC, 1999). Gray arsenic is the ordinary stable form. Arsenic compounds can be categorized as inorganic and organic. Inorganic compounds do not contain an arsenic–carbon bond while organic compounds do.
Физические свойства
Arsenic is classed as a semimetal, meaning that it is neither a metal like aluminum or lead,nor quite a nonmetal such as oxygen, sulfur, or chlorine. Arsenic’s main allotrope is a silverygray,brittle, metal-like substance. Its other two isotopes are unstable crystalline substances.
Gray arsenic exhibits an unusual property in that its boiling point (614°C) is lower than itsmelting point (817°C). As its temperature changes, it sublimates, which means it goes fromthe solid state, skipping the liquid state, into a vapor state. Cooling the vapor of sublimation,the black allotrope condenses out and in turn changes from the black to the gray allotrope. Ifyellow arsenic is rapidly cooled from its sublimation point, yellow arsenic will condense outand will not revert back to gray arsenic upon cooling.
The following information is for the gray semimetal form of arsenic only. Its melting pointis 817°C, its sublimation point varies between 613°C and 814°C depending on the atmosphericpressure, and its density is 5.776 g/cm3.
Изотопы
There are a total of 35 isotopes of arsenic, ranging from As-60 to As-92, withhalf-lives spanning from a few nanoseconds to 80 days. Although some references claimthere are no stable isotopes of arsenic, arsenic-75 is classed as a stable isotope thatmakes up 100% of arsenic found in the Earth’s crust.
Происхождение имени
Derived either from the Latin word arsenicum or the Greek word arsenikon,
both meaning a yellow pigment. It is possible that the Arabic word azzernikh was
also an ancient name for arsenic.
Вхождение
Arsenic is the 53rd most abundant element and is widely distributed in the Earth’s crust.It occurs naturally in several minerals, but high-grade deposits are rare. Most of the mineralsand ores that contain arsenic also contain other metals. Some major sources of arsenic are theminerals orpiment, scherbenkobalt, arsenopyrite, niccolite, realgar, gersdorffite, and smaltite.In addition, most sulfide ores of other metals also contain some arsenic. The three major mineralsthat produce arsenic are: realgar (arsenic monosulfide, AsS), orpiment (arsenic trisulfide,As2S2), and arsenopyrite (iron arsenosulfide, FeAsS).
Today, most arsenic is recovered as a by-product from the smelting of nickel, copper, iron,and tin. It is also recovered from the flue dust of copper- and lead-smelting furnaces.
Характеристики
Arsenic in the elemental form is a brittle, grayish crystal that becomes darker when exposedto air. It is seldom found in the pure elemental form but rather in minerals (compounds). Ithas a long history of use as a poison, and many alchemists were poisoned when using it intheir attempts to produce gold from base metals.
Arsenic has limited commercial use.
Использование
Arsenic is a brittle solid with a metallic coloring that ranges from silver to gray. It is a naturally occurring element found in the earth’s crust, and it cycles rapidly through water, land, air, and living systems. Exposure to it occurs through ingestion, inhalation, and dermal contact.
The arsenic metalloid is used for hardening copper and lead alloys (HSDB, 2005). It is also used in glass manufacturing as a decolorizing and refining agent, as a component of electrical devices in the semiconductor industry, and as a catalyst in the production of ethylene oxide. Arsenic compounds are used as a mordant in the textile industry, for preserving hides, as medicinals, pesticides, pigments, and wood preservatives. The production of chromate copper arsenate (CCA), a wood preservative, accounts for approximately 90% of the domestic arsenic consumption (ATSDR, 2007). However, production of this preservative is being phased out. The uses of inorganic arsenical compounds (e.g., lead arsenate) as pesticides were voluntarily cancelled by the industry during late 1980s and early 1990s. A majority of organoarsenicals are used on cotton and turf as herbicides. disodium methanearsenate (DSMA), monosodium methanearsenate (MSMA), and calcium methanearsenate (CAMA) continue to be used as contact herbicides.
Определение
A toxic metalloid element existing in
several allotropic forms; the most stable is
a brittle gray metal. It belongs to group 15
(formerly VA) of the periodic table. Arsenic
is found native and in several ores including
mispickel (FeSAs), realgar (As4S3),
and orpiment (As2S3). The element reacts
with hot acids and molten sodium hydroxide
but is unaffected by water and acids
and alkalis at normal temperatures. It is
used in semiconductor devices, alloys, and
gun shot. Various compounds are used in
medicines and agricultural insecticides and
poisons.
Symbol: As; m.p. 817°C (gray) at 3
MPa pressure; sublimes at 616°C (gray);
r.d. 5.78 (gray at 20°C); p.n. 33; r.a.m.
74.92159.
Общее описание
A grayish metallic solid that turns black upon exposure to air. Insoluble in water. Toxic by ingestion.
Реакции воздуха и воды
Turns black on exposure to air. Insoluble in water.
Профиль реактивности
Arsenic reacts incandescently with bromine trifluoride, even at 10°C [Mellor 2:113 1946-47]. Causes bromoazide to explode upon contact. Ignites if ground up together with solid potassium permanganate [Mellor 12:322 1946-47]. Is oxidized by sodium peroxide with incandescence [Mellor 2:490-93 1946-47]. A combination of finely divided Arsenic with finely divided bromates (also chlorates and iodates) of barium, calcium, magnesium, potassium, sodium, or zinc can explode by heat, percussion, and friction [Mellor 2:310 1946-47]. Bromine pentafluoride reacts readily in the cold with Arsenic. Ignition usually occurs. Reacts vigorously with fluorine at ordinary temperatures [Mellor 9:34 1946-47].
Опасность
Most of the compounds of arsenic are toxic when in contact with the skin, when inhaled,or when ingested. As with arsenic’s cousin phosphorus above it in group 15 of the periodictable, care must be taken when using arsenic. The compound arsenic trioxide (As2O3), anexcellent weed-killer, is also carcinogenic. Copper acetoarsenite, known as Paris green, is usedto spray cotton for boll weevils. A poisonous dose of arsenic as small as 60 milligrams can bedetected within the body by using the Marsh test.
Промышленное использование
Arsenic (symbol As) is a soft, brittle, poisonouselement of steel-gray color and metallic luster.In atomic structure it is a semimetal, lackingplasticity, and is used only in alloys and incompounds. The bulk of the arsenic used isemployed in insecticides, rat poisons, and weedkillers, but it has many industrial uses, especiallyin pigments. It is also used in poisongases for chemical warfare.Metallic arsenic is stable in dry air. Whenexposed to humid or moistened air, the surfacefirst becomes coated with a superficial goldenbronze tarnish, which on further exposure turnsblack. On heating in air arsenic will vaporizeand burn to As2O3.
Профиль безопасности
Confirmed human
carcinogen producing liver tumors. Poison
by subcutaneous, intramuscular, and
intraperitoneal routes. Human systemic skin
and gastrointestinal effects by ingestion. An
experimental teratogen. Other experimental
reproductive effects. Mutation data
reported. Flammable in the form of dust
when exposed to heat or flame or by
chemical reaction with powerful oxidizers
such as bromates, chlorates, iodates,
peroxides, lithium, NC4, m 0 3 , Khfn04,
Rb2C2, AgN04, NOCl, IF5, CrO3, CIF3,
Cl0, BrF3, BrFj, BrN3, RbGBCH,
CsC3BCH. Slightly explosive in the form of
dust when exposed to flame. When heated
or on contact with acid or acid fumes, it
emits highly toxic fumes; can react
vigorously on contact with oxidizing
materials. Incompatible with bromine azide,
dirubidium acetylide, halogens, palladium,
zinc, platinum, NCh, AgNO3, CrO3, Na2O2,
hexafluoroisopropylideneamino lithum.
Возможный контакт
Arsenic compounds have a variety of
uses. Arsenic and its compounds are used as an alloy additive,
in electronic devices; in veterinary medicines; in agriculture
as insecticides, herbicides, larvicides, and
pesticides. Some arsenic compounds are used in pigment
production; the manufacture of glass as a bronzing or
decolorizing agent; the manufacture of opal glass and
enamels, textile printing; tanning, taxidermy, antifouling
paints; to control sludge formation in lubricating oils.
Metallic arsenic is used as an alloying agent for heavy
metals; and in solders, medicines, herbicides. EPA has estimated
that more than 6 million people living within 12 mi
of major sources of copper, zinc, and lead smelters-may be
exposed to 10 times the average United States atmospheric
levels of arsenic. The agency says that 40,000 people living
near some copper smelters may be exposed to 100 times
the national atmospheric average.
Канцерогенность
Arsenic and inorganic arsenic compounds are known to be human carcinogens based on sufficient evidence of carcinogenicity in humans.
Экологическая судьба
Trivalent arsenic exerts its toxic effects mainly by disrupting
ATP production by inhibiting lipoic acid, which is a cofactor for
pyruvate as well by replacing phosphate which uncouples
oxidation phosphorylation. This inhibits the electron transport
chain in the mitochondria and the ultimate synthesis of ATP.
Hydrogen peroxide production is also increased, which, it is
speculated, has potential to form reactive oxygen species and
oxidative stress. These metabolic interferences lead to death
from multisystem cell death and organ failure. The activity of
enzymes is due to the functional groups on amino acids such as
the sulfhydryl group on cysteine or coenzymes such as lipoic
acid, which has vicinal thiol groups. Trivalent inorganic
arsenicals readily react with sulfhydryl groups such as cysteine
creating a strong complex between arsenic and vicinal sulfhydryl
reagents. These actions inhibit not only the formation of
Acetyl-CoA but also the enzymes succinic dehydrogenase and
pyruvate. Arsenite inhibits the binding of steroids to the
glucocorticoid receptor, but not other steroid receptors. The
probable mechanism of toxicity of pentavalent inorganic
arsenate is its reduction to a trivalent form, arsenite, which is
more toxic than the arsenate. Thus, a variety of mechanisms
lead arsenic to impair cell respiration and subsequently
diminish ATP formation.
Перевозки
UN1558 Arsenic, Hazard Class: 6.1; Labels:
6.1-Poisonous materials.
Несовместимости
Incompatible with strong acids; strong
oxidizers; peroxides, bromine azide, bromine pentafluoride,
bromine trifluoride; cesium acetylene carbide, chromium
trioxide; nitrogen trichloride, silver nitrate. Can react vigorously
with strong oxidizers (chlorine, dichromate, permanganate).
Forms highly toxic fumes on contact with acids or
active metals (iron, aluminum, zinc). Hydrogen gas can
react with inorganic arsenic to form highly toxic arsine gas.
Утилизация отходов
Elemental arsenic wastes
should be placed in long-term storage or returned to
suppliers or manufacturers for reprocessing. Arsenic
pentaselenide-wastes should be placed in long-term storage
or returned to suppliers or manufacturers for reprocessing.
Arsenic trichloride: hydrolyze to arsenic trioxide utilizing
scrubbers for hydrogen chloride abatement. The trioxide
may then be placed in long-term storage. Arsenic trioxide:
long-term storage in large shiftproof and weatherproof
silos. This compound may also be dissolved, precipitated as
the sulfide and returned to the suppliers. Arsenic-containing
sewage may be decontaminated by pyrolusite treatment.
Consult with environmental regulatory agencies for guidance
on acceptable disposal practices. Generators of waste
containing this contaminant (≥100 kg/mo) must conform
with EPA regulations governing storage, transportation,
treatment, and waste disposal. In accordance with
40CFR165, follow recommendations for the disposal of
pesticides and pesticide containers. Must be disposed properly
by following package label directions or by contacting
your local or federal environmental control agency, or by
contacting your regional EPA office.
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