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DIHYDROXIDODIOXIDOCHROMIUM

Dihydroxidodioxidochromium is composed of dark, purplish-red, odorless crystals that are soluble in water.
The specific gravity is 2.7, which is heavier than water.
Dihydroxidodioxidochromium is a powerful oxidizing agent and may explode on contact with organic materials.

CAS Number: 7738-94-5
EC Number: 231-801-5
IUPAC Names: Dihydroxidodioxidochromium
Chemical Formula: H2CrO4

Other names: CHROMIC ACID, Chromic(VI) acid, 7738-94-5, dihydroxy(dioxo)chromium, Chromic acid (H2CrO4), SA8VOV0V7Q, Caswell No. 221, Acide chromique, Acide chromique [French], tetraoxochromic acid, CCRIS 8994, HSDB 6769, EINECS 231-801-5, UNII-SA8VOV0V7Q, EPA Pesticide Chemical Code 021101, AI3-51760, dihydroxidodioxidochromic, dihydrogen(tetraaoxidochromate), [CrO2(OH)2], DTXSID80344, CHEBI:33143, AMY22327, AKOS025243247, J34.508C, CHROMIUM HYDROXIDE OXIDE (CR(OH)2O2), 738C945, Q422642, AI3-51760, HSDB 6769, CCRIS 8994, Cromic acid, CHROMIC ACID, Chromic Acid, Chromic(VI) acid, Chromic acid (H2CrO4), TIANFU-CHEM Chromic acid, dihydroxy(diketo)chromium, EPA Pesticide Chemical Code 021101,

Dihydroxidodioxidochromium is a poison, corrosive to the skin, and has a TLV of 0.05 mg/m3 of air.
Dihydroxidodioxidochromium is a known human carcinogen.
The four-digit UN identification number is 1463.
The NFPA 704 designation is health 3, flammability 0, and reactivity 1.
The white section at the bottom of the 704 diamond has an “oxy” prefix, indicating that Dihydroxidodioxidochromium is an oxidizer.

Hexavalent chromium refers to chromium in the +6 oxidation state, and is more toxic than other oxidation states of the chromium atom because of Dihydroxidodioxidochromium's greater ability to enter cells and a higher redox potential.
Molecular Dihydroxidodioxidochromium, H2CrO4, has much in common with sulfuric acid, H2SO4 as both are classified as strong acids.

Dihydroxidodioxidochromium was widely used in the instrument repair industry, due to its ability to "brighten" raw brass.
A Dihydroxidodioxidochromium dip leaves behind a bright yellow patina on the brass.
Due to growing health and environmental concerns, many have discontinued use of this chemical in their repair shops.
Most Dihydroxidodioxidochromium sold or available as a 10% aqueous solution.

Molecular Weight: 118.010 g/mol
Hydrogen Bond Donor Count: 2
Hydrogen Bond Acceptor Count: 4
Exact Mass: 117.935813 g/mol

Monoisotopic Mass: 117.935813 g/mol
Topological Polar Surface Area: 74.6Å²
Heavy Atom Count: 5
Complexity: 81.3
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes

Dihydroxidodioxidochromium generally refers to a collection of compounds generated by the acidification of solutions containing chromate and dichromate anions or the dissolving of chromium trioxide in sulfuric acid. Dihydroxidodioxidochromium contains hexavalent chromium. Hexavalent chromium refers to chromium in the +6 oxidation state, and is more toxic than other oxidation states of the chromium atom because of its greater ability to enter cells and a higher redox potential.

Molecular Dihydroxidodioxidochromium, H2CrO4, has much in common with sulfuric acid, H2SO4 as both are classified as strong acids. Dihydroxidodioxidochromium was widely used in the instrument repair industry, due to its ability to "brighten" raw brass. A Dihydroxidodioxidochromium dip leaves behind a bright yellow patina on the brass. Due to growing health and environmental concerns, many have discontinued use of this chemical in their repair shops. Most Dihydroxidodioxidochromium sold or available as a 10% aqueous solution.

Dihydroxidodioxidochromium is a dark purplish red solid, exists only in solution.
The hydrate of chromiumoxide, Dihydroxidodioxidochromium is used in electroplating baths.
Dihydroxidodioxidochromium is soluble in water with the release of heat.
The material itself is noncombustible but Dihydroxidodioxidochromium will accelerate the burning of combustible materials.
Dihydroxidodioxidochromium's solution is corrosive to metals and tissue.
A hypothetical acid, H2CrO4, known only in chromatesalts.

Confirmed human carcinogen.
Poison by subcutaneous route.
Mutation data reported.
Dihydroxidodioxidochromium is a powerful oxidzer.
Dihydroxidodioxidochromium is a powerful irritant of skin, eyes, and mucous membranes.
Can cause a dermatitis, bronchoasthma, “chrome holes,” damage to the eyes.

Dihydroxidodioxidochromium is dangerously reactive.
Incompatible with acetic acid, acetic anhydride, tetrahydronaphthalene, acetone, alcohols, alkali metals, ammonia, arsenic, bromine penta fluoride, butyric acid, n,ndimethylformamide, hydrogen sulfide, peroxyformic acid, phosphorus, potassium hexacyanoferrate, pyridme, selenium.

The term Dihydroxidodioxidochromium is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of Dihydroxidodioxidochromium may be used as a cleaning mixture for glass.
Dihydroxidodioxidochromium may also refer to the molecular species, H2CrO4 of which the trioxide is the anhydride.
Dihydroxidodioxidochromium features chromium in an oxidation state of +6 (or VI).
Dihydroxidodioxidochromium is a strong and corrosive oxidising agent and a moderate carcinogen.

The completely protonated form of the dichromate ion is diDihydroxidodioxidochromium, H2Cr2O7 and can also be seen as the result of adding chromium trioxide to molecular Dihydroxidodioxidochromium.
When reacting with an aldehyde or ketone, diDihydroxidodioxidochromium exactly the same way.
In organic chemistry, the Dihydroxidodioxidochromium solution can oxidize primary alcohols to aldehyde and secondary alcohol to a ketone.
but the tertiary alcohols and ketones are unaffected.
During oxidation, the colour of Dihydroxidodioxidochromium changes from orange to brownish green.

Dihydroxidodioxidochromium is capable of oxidising many forms of organic compounds, and many variants have been created for this reagent.
Dihydroxidodioxidochromium is referred to as the Jones reagent in aqueous sulfuric acid and acetone, which oxidises primary and secondary alcohols into carboxylic acids and ketones, respectively, though rarely affecting unsaturated bonds.

Cromyl chloride which is used to test the presence of chloride ions in inorganic chemistry, is derived from Dihydroxidodioxidochromium.
Chromium trioxide and pyridinium chloride produce pyridinium chlorochromate.
This reagent converts to the corresponding aldehydes (R-CHO) primary alcohols.
Dihydroxidodioxidochromium was used to repair musical instruments due to its ability to “brighten” raw brass.

Molecular Dihydroxidodioxidochromium
Molecular Dihydroxidodioxidochromium, H2CrO4, has much in common with sulfuric acid, H2SO4.
Only sulfuric acid can be classified as part of the 7 strong acids list.
Due to the laws pertinent to the concept of "first order ionization energy", the first proton is lost most easily.
Dihydroxidodioxidochromium behaves extremely similarly to sulfuric acid deprotonation.
Since the process of polyvalent acid-base titrations have more than one proton (especially when the acid is starting substance and the base is the titrant), protons can only leave an acid one at a time.

Hence the first step is as follows:

H2CrO4 ⇌ [HCrO4]− + H+
The pKa for the equilibrium is not well characterized.
Reported values vary between about −0.8 to 1.6.
The value at zero ionic strength is difficult to determine because half dissociation only occurs in very acidic solution, at about pH 0, that is, with an acid concentration of about 1 mol dm−3.
A further complication is that the ion [HCrO4]− has a marked tendency to dimerize, with the loss of a water molecule, to form the dichromate ion, [Cr2O7]2−:
2 [HCrO4]− ⇌ [Cr2O7]2− + H2O log KD = 2.05

Furthermore, the dichromate can be protonated:
[HCr2O7]− ⇌ [Cr2O7]2− + H+ pK = 1.8

The pK value for this reaction shows that it can be ignored at pH > 4.

Loss of the second proton occurs in the pH range 4–8, making the ion [HCrO4]− a weak acid.
Molecular Dihydroxidodioxidochromium could in principle be made by adding chromium trioxide to water.

CrO3 + H2O ⇌ H2CrO4
but in practice the reverse reaction occurs when molecular Dihydroxidodioxidochromium is dehydrated.
This is what happens when concentrated sulfuric acid is added to a dichromate solution.
At first the colour changes from orange (dichromate) to red (Dihydroxidodioxidochromium) and then deep red crystals of chromium trioxide precipitate from the mixture, without further colour change.

The colours are due to LMCT transitions.
Chromium trioxide is the anhydride of molecular Dihydroxidodioxidochromium.
Dihydroxidodioxidochromium is a Lewis acid and can react with a Lewis base, such as pyridine in a non-aqueous medium such as dichloromethane.

Dihydroxidodioxidochromium is a dark purplish-red odorless flakes or crystalline powder
The properties are only known to be present in solution.
Obtained by dissolving chromium trioxide in water.
Dihydroxidodioxidochromium's solution is used for chromium plating.

Uses
Chemicals (chromates, oxidizing agents, catalysts), chromium-plating intermediate, medicine (caustic), process engraving, anodizing, ceramic glazes, colored glass, metal cleaning, inks, tanning, paints, textile mordant, etchant for plastics.
Dihydroxidodioxidochromium is an intermediate in chromium plating, and is also used in ceramic glazes, and colored glass.

Because a solution of Dihydroxidodioxidochromium in sulfuric acid (also known as a sulfochromic mixture or chromosulfuric acid) is a powerful oxidizing agent, Dihydroxidodioxidochromium can be used to clean laboratory glassware, particularly of otherwise insoluble organic residues.
This application has declined due to environmental concerns.
Furthermore, the acid leaves trace amounts of paramagnetic chromic ions (Cr3+) that can interfere with certain applications, such as NMR spectroscopy.
Dihydroxidodioxidochromium is especially the case for NMR tubes.

Dihydroxidodioxidochromium was widely used in the musical instrument repair industry, due to its ability to "brighten" raw brass.
A Dihydroxidodioxidochromium dip leaves behind a bright yellow patina on the brass.
Due to growing health and environmental concerns, many have discontinued use of this chemical in their repair shops.

Dihydroxidodioxidochromium was used in hair dye in the 1940s, under the name Melereon.
Dihydroxidodioxidochromium is used as a bleach in black and white photographic reversal processing.
Dihydroxidodioxidochromium is used in the assay for the causes of DNA single-strand breaks during reduction of chromate by glutathione in vitro and in cells.
Also used in the chromium determination in a case of Dihydroxidodioxidochromium ingestion.

Dihydroxidodioxidochromium acts as an intermediate in chromium plating.
Dihydroxidodioxidochromium is used in ceramic glazes and coloured glass.
Chromosulfuric acid or sulfochromic mixture is a strong oxidizing agent that is used to clean laboratory glassware.
Dihydroxidodioxidochromium has the ability to brighten raw brass and therefore it is used in the instrument repair industry.
In the year 1940, Dihydroxidodioxidochromium was used in hair dye.

Reactivity Profile
A very powerful oxidizing agent, confirmed human carcinogen.
Upon contact with reducing reagents Dihydroxidodioxidochromium can cause a violent explosion, in contact with organic matter Dihydroxidodioxidochromium may cause a violent oxidation leading to ignition.
Dangerously reactive with acetone, alcohols, alkali metals (sodium, potassium), ammonia, arsenic, dimethylformamide, hydrogen sulfide, phosphorus, peroxyformic acid, pyridine, selenium, sulfur, and many other chemicals.
When mixed with sulfuric acid for glass cleaning operations, used solution in closed bottle may explode due to internal pressure of carbon dioxide arising from contamination by carbon compounds.

Health Hazard
Very irritating to eyes and respiratory tract.
Ingestion causes severe gastrointestinal symptoms.
Contact with eyes or skin causes burns; prolonged contact produces dermatitis.
A human carcinogen.

Dihydroxidodioxidochromium is a poison.
Dihydroxidodioxidochromium corrosive to skin.
Powerful oxidizing agent, may explode on contact with reducing agents, may ignite on contact with organic materials.
Upper respiratory tract irritant.

Metabolism
Skin contact with Dihydroxidodioxidochromium can cause redness, pain, and severe skin burns.
Dihydroxidodioxidochromium may cause severe burns to the eye and permanent eye damage.
Severe and rapid corrosive burns of the mouth, gullet and gastrointestinal tract will result if Dihydroxidodioxidochromium is swallowed.
Symptoms include burning, choking, nausea, vomiting and severe pain.

Chronic exposure to low levels of Dihydroxidodioxidochromium can lead to chronic exposure to hexavalent chromium.
Hexavalent chromium is a known carcinogen.
Chronic inhalation especially has been linked to lung cancer.
Hexavalent chromium is also known to cause reproductive and developmental defects.

Skin contact can cause redness, pain, and severe skin burns.
Dihydroxidodioxidochromium may cause severe burns to the eye and permanent eye damage.
Severe and rapid corrosive burns of the mouth, gullet and gastrointestinal tract will result if Dihydroxidodioxidochromium is swallowed.
Symptoms include burning, choking, nausea, vomiting and severe pain.