| IUPAC name |
copper hydrogen arsenite
|Other names |
3D model (JSmol)
|US health exposure limits (NIOSH):|
|[1910.1018] TWA 0.010 mg/m3|
|Ca C 0.002 mg/m3 [15-minute]|
IDLH (Immediate danger)
|Ca [5 mg/m3 (as As)]|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Scheele's Green, also called Schloss Green, is chemically a cupric hydrogen arsenite (also called copper arsenite or acidic copper arsenite), CuHAsO
3. It is chemically related to Paris Green. It is a yellowish-green pigment which in the past was used in some paints, but has since fallen out of use because of its toxicity and the instability of its color in the presence of sulfides and various chemical pollutants.
Copper is a chemical element with symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.
In chemistry, an arsenite is a chemical compound containing an arsenic oxoanion where arsenic has oxidation state +3. Note that in fields that commonly deal with groundwater chemistry, arsenite is used generically to identify soluble AsIII anions. IUPAC have recommended that arsenite compounds are to be named as arsenate(III), for example ortho-arsenatite is called trioxidoarsenate(III). Ortho-arsenite contrasts to the corresponding anions of the lighter members of group 15, phosphite which has the structure HPO2−
3 and nitrite, NO−
2 which is bent.
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light. Most materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have special properties that make them useful for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors. It must be stable in solid form at ambient temperatures.
Scheele's Green was invented in 1775 by Carl Wilhelm Scheele.By the end of the 19th century, it had virtually replaced the older green pigments based on copper carbonate.
Carl Wilhelm Scheele was a Swedish Pomeranian and German pharmaceutical chemist. Isaac Asimov called him "hard-luck Scheele" because he made a number of chemical discoveries before others who are generally given the credit. For example, Scheele discovered oxygen, and identified molybdenum, tungsten, barium, hydrogen, and chlorine before Humphry Davy, among others. Scheele discovered organic acids tartaric, oxalic, uric, lactic, and citric, as well as hydrofluoric, hydrocyanic, and arsenic acids. He preferred speaking German to Swedish his whole life, as German was commonly spoken among Swedish pharmacists.
Basic copper carbonate is a chemical compound, more properly called copper(II) carbonate hydroxide. It is an ionic compound consisting of the ions copper(II) Cu2+
, carbonate CO2−
3, and hydroxide HO−
The pigment was originally prepared by making a solution of sodium carbonate at a temperature of around 90 °C, then slowly adding arsenious oxide, while constantly stirring until everything had dissolved. This produced a sodium arsenite solution. Added to a copper sulfate solution, it produced a green precipitate of effectively insoluble copper arsenite. After filtration the product was dried at about 43 °C. To enhance the color, the salt was subsequently heated to 60–70 °C. The intensity of the color depends on the copper : arsenic ratio, which in turn was affected by the ratio of the starting materials, as well as the temperature.
Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, water-soluble salts. All forms have a strongly alkaline taste and give moderately alkaline solutions in water. Historically it was extracted from the ashes of plants growing in sodium-rich soils. Because the ashes of these sodium-rich plants were noticeably different from ashes of wood (once used to produce potash), sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process.
Arsenic trioxide is an inorganic compound with the formula As
3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tonnes are produced annually. Many applications are controversial given the high toxicity of arsenic compounds.
Sodium arsenite usually refers to the inorganic compound with the formula NaAsO2. Also called sodium meta-arsenite, it is the sodium salt of arsenous acid. Sodium ortho-arsenite is Na3AsO3. The compounds are colourless solids.
It has been found that Scheele's green was composed of a variety of different compounds, including copper metaarsenite (CuO·As
3), copper arsenite salt (CuHAsO
3 and Cu(AsO
2O)), neutral copper orthoarsenite (3CuO·As
2O), copper arsenate (CuAsO
2 and Cu(AsO
2), and copper diarsenite (2CuO·As
Scheele's Green was used as a color for paper, e.g. for wallpapers and paper hangings, and in paints, wax candles, and even on some children's toys.It was also used to dye cotton and linen. Scheele's Green is more brilliant and durable than the then-used copper carbonate pigments. However, because of its copper content it tends to fade and blacken when exposed to sulfides, whether in the form of atmospheric hydrogen sulfide or in pigment mixtures based on or containing sulfur.
Sulfide (British English sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. Sulfide also refers to chemical compounds large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH-) are the conjugate acids of sulfide.
Hydrogen sulfide is the chemical compound with the formula H
2S. It is a colorless chalcogen hydride gas with the characteristic foul odor of rotten eggs. It is very poisonous, corrosive, and flammable.
Sulfur or sulphur is a chemical element with symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature.
Emerald green, also known as Paris Green, was developed later in an attempt to improve Scheele's Green. It had the same tendency to blacken, but was more durable. By the end of the 19th century, both greens were made obsolete by cobalt green, also known as zinc green, which is far less toxic.
Paris green is an inorganic compound. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment, despite its toxicity. It is also used as a blue colorant for fireworks. The color of Paris green is said to range from a pale blue green when very finely ground, to a deeper green when coarsely ground.
Cobalt green is an ambiguous term for either of two families of green inorganic pigments. Both are obtained by doping cobalt(II) oxide into colorless host oxides.
Scheele's Green was used as an insecticide in the 1930s, together with Paris Green.
Despite evidence of its high toxicity, Scheele's Green was also used as a food dye for sweets such as green blancmange,a fondness of traders in 19th-century Greenock; this led to a long-standing Scottish prejudice against green sweets.
In the 19th century, the toxicity of arsenic compounds was not readily known. Nineteenth-century journals contained reports of children wasting away in bright green rooms, of ladies in green dresses swooning and newspaper printers being overcome by arsenic vapors. There is one example of an acute poisoning of children attending a Christmas party where dyed candles were burned.
Two main theories on the cause of wallpaper poisoning events have been proposed: dust particles caused by pigment and paper flaking, and toxic gas production. Tiny particles of the pigment can flake off and become airborne, and then are absorbed by the lungs. Alternatively, toxic gas can be released from compounds containing arsenic following certain chemical processes, such as heating, or metabolism by an organism. When the wallpaper becomes damp and moldy, the pigment may be metabolised, causing the release of poisonous arsine gas (AsH
3). Fungi genera such as Scopulariopsis or Paecilomyces release arsine gas, when they are growing on a substance containing arsenic. The Italian physician Bartolomeo Gosio published in 1893 his results on "Gosio gas", that was subsequently shown to contain trimethylarsine. Under wet conditions, the mold Scopulariopsis brevicaulis produced significant amounts of methyl arsines via methylation of arsenic-containing inorganic pigments, especially Paris green and Scheele's Green.
In these compounds, the arsenic is either pentavalent or trivalent (arsenic is in group 15), depending on the compound. In humans, arsenic of these valences is readily absorbed by the gastrointestinal tract, which accounts for its high toxicity. Pentavalent arsenic tends to be reduced to trivalent arsenic and trivalent arsenic tends to proceed via oxidative methylation in which the trivalent arsenic is made into mono, di and trimethylated products by methyltransferases and an S-adenosyl-methionine methyl donating cofactor.However, newer studies indicate that trimethylarsine has a low toxicity, and could therefore not account for the death and the severe health problems observed in the 19th century.
Arsenic is not only toxic, but it also has carcinogenic effects.
During Napoleon's exile in St. Helena, he resided in a house in which the rooms were painted bright green, his favorite color. The cause of his death is generally believed to be stomach cancer, and arsenic exposure has been linked to an increased risk of gastric carcinoma. Analysis of samples of his hair revealed significant amounts of arsenic. As St. Helena has a rather damp climate, it is likely that fungus grew on the walls. It has also been suggested that the presence of such abnormally high levels of arsenic might be due to attempts at preserving his body.
The Marsh test is a highly sensitive method in the detection of arsenic, especially useful in the field of forensic toxicology when arsenic was used as a poison. It was developed by the chemist James Marsh and first published in 1836.
Arsine (IUPAC name: arsane) is an inorganic compound with the formula AsH3. This flammable, pyrophoric, and highly toxic pnictogen hydride gas is one of the simplest compounds of arsenic. Despite its lethality, it finds some applications in the semiconductor industry and for the synthesis of organoarsenic compounds. The term arsine is commonly used to describe a class of organoarsenic compounds of the formula AsH3−xRx, where R = aryl or alkyl. For example, As(C6H5)3, called triphenylarsine, is referred to as "an arsine".
A blood agent is a toxic chemical agent that affects the body by being absorbed into the blood. Blood agents are fast-acting, potentially lethal poisons that typically manifest at room temperature as volatile colorless gases with a faint odor. They are either cyanide- or arsenic-based.
Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over time. It is usually a basic copper carbonate, but near the sea will be a basic copper chloride. If acetic acid is present at the time of weathering, it may consist of copper(II) acetate.
Stibine (IUPAC name: stibane) is a chemical compound with the formula SbH3. A pnictogen hydride, this colourless gas is the principal covalent hydride of antimony, and a heavy analogue of ammonia. The molecule is pyramidal with H–Sb–H angles of 91.7° and Sb–H distances of 170.7 pm (1.707 Å). This gas has an offensive smell like hydrogen sulfide (rotten eggs).
Arsenic pentoxide is the inorganic compound with the formula As2O5. This glassy, white, deliquescent solid is relatively unstable, consistent with the rarity of the As(V) oxidation state. More common, and far more important commercially, is arsenic(III) oxide (As2O3). All arsenic compounds are highly toxic and thus find only limited commercial applications.
Copper arsenate (Cu3(AsO4)2.4H2O, or Cu5H2(AsO4)4.2H2O), also called copper orthoarsenate, tricopper arsenate, cupric arsenate, or tricopper orthoarsenate, is a blue or bluish-green powder insoluble in water and alcohol and soluble in aqueous ammonium and dilute acids. Its CAS number isor .
Trimethylarsine (abbreviated TMA or TMAs) is the chemical compound with the formula (CH3)3As, commonly abbreviated AsMe3 or TMAs. This organic derivative of arsine has been used as a source of arsenic in microelectronics industry, a building block to other organoarsenic compounds, and serves as a ligand in coordination chemistry. It has distinct "garlic"-like smell. Trimethylarsine had been discovered as early as 1854.
Potassium arsenite (KAsO2) is an inorganic compound that exists in two forms, potassium meta-arsenite (KAsO2) and potassium ortho-arsenite (K3AsO3). It is composed of arsenite ions (AsO33− or AsO2−) with arsenic always existing in the +3 oxidation state, and potassium existing in the +1 oxidation state. Like many other arsenic containing compounds, potassium arsenite is highly toxic and carcinogenic to humans. Potassium arsenite forms the basis of Fowler’s solution, which was historically used as a medicinal tonic, but due to its toxic nature its use was discontinued. Potassium arsenite is still, however, used as a rodenticide.
Organoarsenic chemistry is the chemistry of compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herbicides, and fungicides. In general these applications are declining in step with growing concerns about their impact on the environment and human health. The parent compounds are arsine and arsenic acid. Despite their toxicity, organoarsenic biomolecules are well known.
Pietro Biginelli was an Italian chemist, who discovered a three-component reaction between urea, acetoacetic ester and aldehydes. He also was studying various aspects of sanitation chemistry and chemical products' quality control.
Methyldichloroarsine, sometimes abbreviated "MD", is an organoarsenic compound with the formula CH3AsCl2. This colourless volatile liquid is a highly toxic vesicant that has been used in chemical warfare.
Arsenic biochemistry refers to biochemical processes that can use arsenic or its compounds, such as arsenate. Arsenic is a moderately abundant element in Earth's crust, and although many arsenic compounds are often considered highly toxic to most life, a wide variety of organoarsenic compounds are produced biologically and various organic and inorganic arsenic compounds are metabolized by numerous organisms. This pattern is general for other related elements, including selenium, which can exhibit both beneficial and deleterious effects. Arsenic biochemistry has become topical since many toxic arsenic compounds are found in some aquifers, potentially affecting many millions of people via biochemical processes.
Bartolomeo Gosio was an Italian medical scientist. He discovered a toxic fume, eponymously named "Gosio gas", which is produced by microorganisms, that killed many people. He identified the chemical nature of the gas as an arsenic compound (arsine), but incorrectly named it as diethylarsine. He also discovered an antibacterial compound called mycophenolic acid from the mould Penicillium brevicompactum. He demonstrated that the novel compound was effective against the deadly anthrax bacterium, Bacillus anthracis. This was the first antibiotic compound isolated in pure and crystallised form. Though the original compound was abandoned in clinical practice due to its adverse effects, its chemical derivative mycophenolate mofetil became the drug of choice as an immunosuppressant in kidney, heart, and liver transplantations.