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Chromic acid, CrO3, is composed of dark, purplish-red, odorless crystals that are soluble in water.
The specific gravity is 2.7, which is heavier than water.
Chromic acid is a powerful oxidizing agent and may explode on contact with organic materials.
CAS: 7738-94-5
MF: H2CrO4
MW: 118.01
EINECS: 231-801-5
Chromic acid is a poison, corrosive to the skin, and has a TLV of 0.05 mg/m3 of air.
Chromic acid 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 Chromic acid is an oxidizer.
Chromic acid 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.
Chromic acid 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 Chromic acid's greater ability to enter cells and a higher redox potential.
Molecular chromic acid, H2CrO4, has much in common with sulfuric acid, H2SO4 as both are classified as strong acids.
Chromic acid was widely used in the instrument repair industry, due to its ability to "brighten" raw brass.
A chromic acid 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 chromic acid sold or available as a 10% aqueous solution.
Chromic acid is a dark purplish red solid, exists only in solution.
The hydrate of chromiumoxide, Chromic acid is used in electroplating baths.
Chromic acid is soluble in water with the release of heat.
The material itself is noncombustible but Chromic acid will accelerate the burning of combustible materials.
Chromic acid'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.
Chromic acid is a powerful oxidzer.
Chromic acid is a powerful irritant of skin, eyes, and mucous membranes.
Can cause a dermatitis, bronchoasthma, “chrome holes,” damage to the eyes.
Chromic acid 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 chromic acid 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 chromic acid may be used as a cleaning mixture for glass.
Chromic acid may also refer to the molecular species, H2CrO4 of which the trioxide is the anhydride.
Chromic acid features chromium in an oxidation state of +6 (or VI).
Chromic acid is a strong and corrosive oxidising agent and a moderate carcinogen.
The completely protonated form of the dichromate ion is dichromic acid, H2Cr2O7 and can also be seen as the result of adding chromium trioxide to molecular chromic acid.
When reacting with an aldehyde or ketone, dichromic acid exactly the same way.
In organic chemistry, the chromic acid 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 chromic acid changes from orange to brownish green.
Chromic acid is capable of oxidising many forms of organic compounds, and many variants have been created for this reagent.
Chromic acid 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 chromic acid.
Chromium trioxide and pyridinium chloride produce pyridinium chlorochromate.
This reagent converts to the corresponding aldehydes (R-CHO) primary alcohols.
Chromic acid was used to repair musical instruments due to its ability to “brighten” raw brass.
Molecular Chromic acid
Molecular chromic acid, 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.
Chromic acid 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[4]
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 chromic acid could in principle be made by adding chromium trioxide to water.
CrO3 + H2O ⇌ H2CrO4
but in practice the reverse reaction occurs when molecular chromic acid 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 (chromic acid) 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 chromic acid.
Chromic acid is a Lewis acid and can react with a Lewis base, such as pyridine in a non-aqueous medium such as dichloromethane.
Chromic acid Chemical Properties
Melting point: 196°C
Density: 2.290
Form: Liquid
Color: Clear, orange
PH: 3.03(1 mM solution);2.33(10 mM solution);2.06(100 mM solution)
Water Solubility: HIGHLY Soluble
EPA Substance Registry System: Chromic(VI) acid (7738-94-5)
Chromic acid 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.
Chromic acid'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.
Chromic acid is an intermediate in chromium plating, and is also used in ceramic glazes, and colored glass.
Because a solution of chromic acid in sulfuric acid (also known as a sulfochromic mixture or chromosulfuric acid) is a powerful oxidizing agent, Chromic acid 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.
Chromic acid is especially the case for NMR tubes.
Chromic acid was widely used in the musical instrument repair industry, due to its ability to "brighten" raw brass.
A chromic acid 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.
Chromic acid was used in hair dye in the 1940s, under the name Melereon.
Chromic acid is used as a bleach in black and white photographic reversal processing.
Chromic Acid 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 chromic acid ingestion.
Chromic acid acts as an intermediate in chromium plating.
Chromic acid 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.
Chromic acid has the ability to brighten raw brass and therefore it is used in the instrument repair industry.
In the year 1940, Chromic acid was used in hair dye.
Reactivity Profile
A very powerful oxidizing agent, confirmed human carcinogen.
Upon contact with reducing reagents Chromic acid can cause a violent explosion, in contact with organic matter Chromic acid 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.
Chromic acid is a poison.
Chromic acid 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 chromic acid can cause redness, pain, and severe skin burns.
Chromic acid 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 chromic acid is swallowed.
Symptoms include burning, choking, nausea, vomiting and severe pain.
Chronic exposure to low levels of chromic acid 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.
Chromic acid 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 chromic acid is swallowed.
Symptoms include burning, choking, nausea, vomiting and severe pain.
Synonyms
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
