CHROMIC ACID
CHROMIC ACID
Chromic acid is an inorganic acid composed of the elements chromium, oxygen, and hydrogen.
Chromic acid is a dark, purplish red, odorless, sand-like solid powder.
When dissolved in water, Chromic acid is a strong acid.
CAS Number: 7738-94-5
EC Number: 231-801-5
Chemical Formula: H2CrO4
Molecular Weight: 118.010 g/mol
Synonyms: CHROMIC ACID, Chromic(VI) acid, 7738-94-5, dihydroxy(dioxo)chromium, Acide chromique, Caswell No. 221, Chromic acid (H2CrO4), tetraoxochromic acid, CCRIS 8994, HSDB 6769, UNII-SA8VOV0V7Q, SA8VOV0V7Q, EINECS 231-801-5, EPA Pesticide Chemical Code 021101, AI3-51760, dihydroxidodioxidochromium, dihydrogen(tetraaoxidochromate), DTXSID8034455, CHEBI:33143, J34.508C, CHROMIUM HYDROXIDE OXIDE (CR(OH)2O2), (CrO2(OH)2), [CrO2(OH)2], Acide chromique [French], Chromium hydrogen oxide, Pesticide Code: 021101, DTXCID6014455, KRVSOGSZCMJSLX-UHFFFAOYSA-L, AMY22327, AKOS025243247, Q422642, Chromic acid [Wiki], 231-801-5 [EINECS], 7738-94-5 [RN], chromic acid (H2CrO4), Chromium, dihydroxydioxo- [ACD/Index Name], Dihydroxy(dioxo)chrom [German] [ACD/IUPAC Name], Dihydroxy(dioxo)chrome [French] [ACD/IUPAC Name], Dihydroxy(dioxo)chromium [ACD/IUPAC Name], SA8VOV0V7Q, [CrO2(OH)2], 11115-74-5 [RN], 1333-82-0 [RN], 13530-68-2 [RN], 13765-19-0 [RN], 199384-58-2 [RN], 237391-94-5 [RN], 24934-60-9 [RN], 9044-10-4 [RN], Acide chromique [French], chromate [Wiki], Chromatite syn, CHROMIC ACID|DIOXOCHROMIUMDIOL, CHROMIC ANHYDRIDE, chromic(VI) acid, Chromium hydroxide oxide, Chromium trioxide [Wiki], dihydrogen(tetraaoxidochromate), dihydrogen(tetraaoxidochromate); dihydroxidodioxidochromium, dihydroxidodioxidochromium, dihydroxy-dioxochromium, dihydroxy-dioxo-chromium, Gelbin, H2CrO4, SOLID CHROMIC ACID, tetraoxochromic acid, UNII:SA8VOV0V7Q, UNII-SA8VOV0V7Q, Yellow ultramarine, 铬酸 [Chinese]
Chromic acid is a very weak acid and Chromic acid salts can be dissociated event by acetic acid.
Chromic acid has a strong oxidising action and is itself reduced to CrO3; because of this, Chromic acid should never be used in combination with alcohol or formalin.
Chromic acid is an inorganic acid composed of the elements chromium, oxygen, and hydrogen.
Chromic acid is a dark, purplish red, odorless, sand-like solid powder.
When dissolved in water, Chromic acid is a strong acid.
There are 2 types of chromic acid: molecular chromic acid with the formula H2CrO4 and dichromic acid with the formula H2Cr2O7.
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.
Chromic acid is formed when chromium trioxide reacts with water.
Chromium trioxide is crystalline, light red or brown in color and is deliquescent and fully soluble in water.
In a number of fixing fluids, however, chromic acid is used together with formalin–the reducing action being slow, the fixation is completed before the acid is fully reduced.
Chromic acid is a strong precipitant of protein but Berg (1927) found Chromic acid to be a very weak precipitant of nuclein.
The dissociation of chromic acid in water may result in H+ and HCrO4− or 2H+ and CrO4− ions.
According to Berg (1927), protein undergoes denaturation and precipitation by the primary action of chromic acid, and the secondary action results in hardening.
He holds that the ion HCrO4− is responsible for the secondary action.
Chemical reaction probably occurs between protein and chromic acid, but the exact steps are not precisely known.
However, the principal affinity of chromium is for the carboxyl and hydroxyl groups.
Green (1953) suggested that coordinates with –OH and –NH2 are formed after reaction with carboxyl groups.
Proteins, acted upon by chromic acid, are resistant to the action of pepsin and trypsin.
Chromic acid penetrates the tissues slowly and the hardening induced by this acid makes the tissue resistant to hardening by ethanol in subsequent processing.
Chromic acid does not cause excessive shrinkage of the tissue.
Materials fixed in this acid require thorough washing in water, at least overnight, otherwise the deposition of chromic crystals not only hinders staining but also hampers the observation of chromosomes.
Because of Chromic acid slight hardening action Chromic acid is difficult to use this fluid as a fixative for squash preparations, unless softened by some strong acid, which may hamper staining.
Chromic acid should never be used alone, as then heavy precipitates are formed causing shrinkage of nucleus and cytoplasm.
Materials treated in chromic acid should not be kept in strong sunlight due to the chance of breakdown of proteins.
Basic dyes adhere closely to tissue fixed in chromic acid.
In general, chromic acid is considered an essential ingredient of several fixing mixtures.
Chromic acid imparts a better consistency to the tissue and aids staining better than osmium tetroxide.
Synonymous with concentrated sulfuric acid, the term chromic acid refers to a mixture formed by adding concentrated sulfuric acid to a dichromate solution that contains a variety of compounds, including solid chromium trioxide.
Chromic acid is possible to use this type of chromic acid to clean glass with a cleaning solution.
Chromic acid is an inorganic compound with the chemical formula H2CrO4 and is a compound compound.
Tetraoxo Chromic acid, also known as Chromic(VI) acid, is another name for chromic acid.
This article discusses the structure, preparation, properties, and various applications of chromic acid.
Chromic acid has a +6 (or VI) chromium oxidation state, which is also known as the hexavalent chromium oxidation state.
Chromium can exist in a number of different oxidation states, with +6 being the most extreme.
Chromic acid is used to oxidise a wide range of organic compounds, the most common of which are alcohols.
Chromic acid is a powerful oxidising agent that is effective against a wide range of organic compounds.
Using chromic acid as an oxidant, there are two basic principles that can be applied to any alcohol.
The oxidation of any alcohol containing approximately one alpha hydrogen occurs in the presence of chromic acid, which means that tertiary alcohols do not undergo oxidation in the presence of the acid.
The oxidation of any organic product formed, whose molecule contains at least one hydrogen atom bound to the carbonyl carbon, is further enhanced by chromic acid.
Chromic Acid is also called Tetraoxochromic acid or Chromic(VI) acid.
Chromic acid is usually a mixture made by adding concentrated sulphuric acid (H2SO4) to a dichromate which consists of a variety of compounds and solid chromium trioxide.
The term chromic acid is generally used for a mixture made by the addition of concentrated sulfuric acid in a dichromate that may contain various compounds, including solid chromium trioxide.
This type of chromic acid can be used as a cleaning mixture for glass.
Chromic acid can also be related to a molecular species, H2CrO4, which is the trioxide anhydride.
Chromic acid contains chromium in the +6 (or VI) oxidation state.
Chromic acid is a strong and corrosive oxidizing agent.
The anhydride of chromic acid is chromium trioxide (CrO3).
Therefore, when chromic acid is mentioned, CrO3 comes to mind.
Here chromium has (6+) valency.
Chromic acid is an unstable compound and turns into di(bi) chromatic acid (H2Cr2O7) by reacting with itself.
Chromic acid anhydride (CrO3) is a red-pink crystal and Chromic acid specific gravity is between 2.67 and 2.82 g/cm3.
Chromic acid melts at 197°C and slowly decomposes after melting.
Chromic acid draws moisture from the air.
Chromic acid is very soluble in water and organic solvents such as acetic acid, pyridine and ether.
Crude CrO3 is separated by precipitation from a mixture of saturated sulfate acid and saturated sodium bichromate.
This precipitate is purified by crystallization or melting.
Chromic acid is a strong acid and is also a strong oxidizing agent.
Chromic acid is highly destructive to plant and animal cells.
If Chromic acid is brought into contact with an organic compound or by reduction, a serious explosion may occur.
Chromic acid is a chromium oxoacid.
Chromic acid has a role as an oxidising agent.
Chromic acid is a conjugate acid of a hydrogenchromate.
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 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 Chromic acid 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.
Also known as Tetraoxochromic or Chromic (VI) acid, Chromic acid is a dark red purplish solid with Chromic acid solution being corrosive to tissue and metals.
Chromic acid is a naturally occurring oxide but can also be made by adding concentrated sulphuric acid to a dichromate which may contain a mixture of compounds such as the solid chromium trioxide.
Chromic Acid usually refers to a collection of compounds formed via the dissolution of Chromium Trioxide in Sulfuric Acid, or via the acidification of Chromate/Dichromate solutions.
Chromic acid is a dark red, strongly corrosive liquid.
Since Chromic acid contains chromium in Chromic acid +6 oxidation state, Chromic acid has strong oxidizing properties and a high redox potential.
Hence, Chromic Acid has been used as a cleaning reagent for lab glassware, textiles, and metals, and an oxidizing agent in organic chemistry reactions.
For a time, Chromic acid was commonly used in musical instrument repair to brighten brass, and as a bleach in photograph development.
The properties that lend this compound to these applications also increase Chromic acid toxicity due to Chromic acid increased ability to enter cells, so some industries have phased in out in favor of alternatives.
Chromic acid is generally available in relatively dilute solutions.
Chromic acid solution is a type of acid that consists of a mixture of concentrated sulfuric acid with dichromate and can contain many different compounds such as solid chromium trioxide.
Chromic acid is a very good cleaner for windows.
Chromic acid can also refer to the molecular species H2CrO4 where the trioxide is anhydride.
Chromic acid contains chromium in the +6-valent oxidation state, which is a strong and corrosive oxidizing agent.
Since Chromic acid is not a stable compound, Chromic acid reacts with itself and turns into dichromatic acid.
Chromic acid has a melting point of 197 degrees and due to Chromic acid chemical properties, Chromic acid absorbs moisture from the air and decomposes slowly when Chromic acid melts.
Chromic acid is very soluble in organic solvents such as chromic acid, pyridine, ether, acetic acid and water.
Chromic acid is a strong acid solution that can also be used for oxidation.
Chromic acid can be corrosive and harmful to living species such as animals and plants.
There is a possibility of creating a massive explosion if Chromic acid comes into contact with an organic compound or through reduction.
Chromic acid should be stored in a dry and cool environment.
Chromic acid should be protected from heat and direct sunlight.
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 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 Chromic acid 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.
Dichromic acid:
Dichromic acid, H2Cr2O7 is the fully protonated form of the dichromate ion and also can be seen as Chromic acid of adding chromium trioxide to molecular chromic acid.
Dichromic acid will behave the same exact way when reacting with a primary or secondary alcohol.
The caveat to this statement is that a secondary alcohol will be oxidized no further than a ketone, whereas a primary alcohol will be oxidized to a aldehyde for the first step of the mechanism and then oxidized again to a carboxylic acid, contingent on no significant steric hindrance impeding this reaction.
Dichromic acid undergoes the following reaction:
[Cr2O7]2− + 2H+ ⇌ H2Cr2O7 ⇌ H2CrO4 + CrO3
Chromic acid is probably present in chromic acid cleaning mixtures along with the mixed chromosulfuric acid H2CrSO7.
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
The pK value for this reaction shows that Chromic acid 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 (cf. manufacture of sulfuric acid).
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 (Collins reagent).
Chromic acid is a strong oxidizing agent.
Chromic acid is formed when chromium trioxide reacts with water.
Chromic acid chemical formula is H2CrO4.
Chromic acid is used to oxidize many classes of organic compounds.
Chromic acid is an intermediate in chromium plating.
Chromic acid generally refers to a collection of compounds generated by the acidification of solutions containing chromate and dichromate anions.
Chromic acid forms dark purplish red crystals.
Chromic acid and Chromic acid salts are used in electroplating.
Applications of Chromic acid:
In chemistry trade, chromic acid is used in chromate, which is salt of chromic acid, production.
A large portion of chromic acid’s production is used for chrome coating.
Chromic acid is used as burner in medical fields due to Chromic acid being a good oxidizing agent.
Chromic acid is also efficient in cleaning organic filth from glasses in labs but this method is not preferred because of Chromic acid harm to environment.
Chromic acid is also used as rubber pigment in carving processes, salt glaze making, colorizing glasses, cleaning metals, ink and dye productions.
Chromic acid is acquired from adding additive chemicals to chrome trioxide’s aquenous solution.
Chrome trioxde is generally produced by putting 2,4 mol sodium dichromate and 2,8 mol sulphuric acid.
Chromic acid is an intermediate in chromium plating and is also used in ceramic glazes, and colored glass.
Chromic acid can be used to clean laboratory glass ware, particularly of otherwise insoluble organic residues
Chromic acid has also been widely used in the band instrument repair industry, due to Chromic acid ability to “brighten” raw brass.
Chromic acid is used as wood preservative
Chromic acid is a strong oxidizing agent finding application in organic synthesis.
Chromic acid is used for preparation of other chrome chemicals of analytical grades.
Chromic acid is used in chemicals (chromates, oxidizing agents, catalysts), chrome plating, intermediates, pharmaceuticals (caustic), process engraving, anodizing, ceramic glazes, colored glass, metal cleaning, inks, tanning, dyes, textile mordant and plastics.
Chromic acid is used in coating agents, surface treatment agents and surfactants.
Uses of Chromic acid:
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.
This is especially the case for NMR tubes.
Piranha solution can be used for the same task, without leaving metallic residues behind.
Chromic acid was widely used in the musical instrument repair industry, due to Chromic acid 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 electroplating, metal cleaning, leather tanning, and photography.
Chromic acid is an intermediate in chromium plating, and is also used in ceramic glazes, and colored glass.
Chromic acid is used in ceramic glazes.
Chromic acid is used as a photographic chemical.
Chromic acid is used as an oxidizing agent.
Chromic acid is used as a cleaner in the laboratory.
Chromic acid is used in the metal finishing industry.
Chromic acid is used in the leather tanning, electroplating, and anticorrosive metal treatment industries.
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 Chromic acid is used in the instrument repair industry.
In the year 1940, Chromic acid was used in hair dye.
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.
Chromic acid converts to the corresponding aldehydes (R-CHO) primary alcohols.
Chromic acid was used to repair musical instruments due to Chromic acid ability to “brighten” raw brass.
Chromic Acid is used in to manufacture metal and plastic coatings to produce a strong, tarnish-resistant, chrome finish.
Chromic acid finds applications in many industries including in the manufacture of appliances and automobiles.
Chromic acid is also used as a wood preservative for marine pilings, telephone poles, landscape timbers and other industrial wood applications.
Being a strong oxidizing agent, Chromic acid also finds applications in organic synthesis and for preparation of other chrome chemicals of analytical grades.
Usage areas:
Chromic acid is used in the chemical industry to manufacture chromates, which are salts of chromic acid.
Most chromic acid is produced for use in chrome plating.
Chromic acid is used as a caustic in medicine,
Chromic acid is used in carving processes,
Chromic acid is used in making ceramic glaze,
Chromic acid is used in tinting windows,
Chromic acid is used in cleaning metals,
Chromic acid is used in ink and paint manufacturing
Chromic acid is used as rubber pigment.
In the chemical industry, chromic acid is used for the manufacture of chromates, the salt form of Chromic acid.
The area where chromic acid is used most in the market is the chrome plating process.
Chromic acid is used as a caustic agent in the medical industry.
Chromic acid is used during the glazing process during the production stages of handicrafts such as carving and ceramics.
Chromic acid is used in the coloring phase of the glass production process.
Chromic acid is used in the cleaning of metals.
Chromic acid is used in paint and ink production.
Chromic acid is used as a pigment in the production of rubber material.
Industrial Processes with risk of exposure:
Acid and Alkali Cleaning of Metals
Electroplating
Leather Tanning and Processing
Photographic Processing
Textiles (Printing, Dyeing, or Finishing)
Activities with risk of exposure:
Textile arts
General Properties of Chromic acid:
Chromic acid generally refers to a mixture produced by adding concentrated sulphuric acid to a dichromate.
Dichromate may contain several other compounds such as solid chromium trioxide.
Chromic acid is a very good chemical for glass cleaning.
Anhydrous form of trioxide(H2CrO4) can also be called chromic acid.
Chromic acid is a strong and abrasive oxidizing agent.
Chemically, Chromic acid bear may remeblance to sulphuric acid and acts simlarly when yielding hydrogen.
Only sulphuric acid yields first proton much easier than chromic acid.
Additionally, chromic acid slowly disintigrates while reaching boiling point and, in proper environments, Chromic acid becomes dessicant.
Formula of Chromic acid:
Hydrogen is a chemical element with the symbol H and Chromic acid atomic number is 1 and Chromic acid electron configuration is 1s.
Chromic acid is the lightest element.
Chromic acid is colorless, odorless, tasteless, non-toxic, and highly combustible.
Chromic acid is an extremely flammable gas, Chromic acid burns in the air and oxygen to produce water.
Chromic acid is used in the synthesis of Ammonia and the manufacturing of Nitrogenous fertilizers.
Chromic acid is used as rocket fuel and is used in the production of hydrochloric acid.
Chromium is a chemical element with the symbol Cr.
Chromic acid atomic number is 24 and Chromic acid electronic configuration is [Ar]3d5 4s.
Chromic acid is a steely gray, lustrous, hard, and brittle transition metal.
Chromic acid is not found as a free element in nature but is found in the form of ores.
The main ore of chromium is Chromite.
Oxygen is a chemical element with the symbol O and the atomic number is 8.
Chromic acid is a colorless, odorless, tasteless gas essential to living organisms.
Chromic acid is a reactive element that is found in water, in most rocks and minerals, and in numerous organic compounds.
Chromic acid is the most abundant element in the earth’s crust.
Chromic acid is life-supporting gas and highly combustible.
Structure of Chromic acid:
Chromic Acid is a strong oxidizing agent.
Chromic acid is an acid so Chromic acid begins with H.
Next, we look at the name there is no prefix in front of the chromic acid.
Acids all contain hydrogen.
In this structure hydrogen bonded with chromate.
The structure of chromic acid starts with four oxygen atoms bonded to chromium.
Two of them have double bonds, and two have single bonds.
They singly bonded oxygen atoms each have a hydrogen bonded to them.
Reactions of Chromic acid:
Chromic acid is capable of oxidizing many kinds of organic compounds and many variations on this reagent have been developed:
Chromic acid in aqueous sulfuric acid and acetone is known as the Jones reagent, which will oxidize primary and secondary alcohols to carboxylic acids and ketones respectively, while rarely affecting unsaturated bonds.
Pyridinium chlorochromate is generated from chromium trioxide and pyridinium chloride.
This reagent converts primary alcohols to the corresponding aldehydes (R–CHO).
Collins reagent is an adduct of chromium trioxide and pyridine used for diverse oxidations.
Chromyl chloride, CrO2Cl2 is a well-defined molecular compound that is generated from chromic acid.
Illustrative transformations:
Oxidation of methylbenzenes to benzoic acids.
Oxidative scission of indene to homophthalic acid.
Oxidation of secondary alcohol to ketone (cyclooctanone) and nortricyclanone.
Use in qualitative organic analysis:
In organic chemistry, dilute solutions of chromic acid can be used to oxidize primary or secondary alcohols to the corresponding aldehydes and ketones.
Similarly, Chromic acid can also be used to oxidize an aldehyde to Chromic acid corresponding carboxylic acid.
Tertiary alcohols and ketones are unaffected.
Because the oxidation is signaled by a color change from orange to brownish green (indicating chromium being reduced from oxidation state +6 to +3), chromic acid is commonly used as a lab reagent in high school or undergraduate college chemistry as a qualitative analytical test for the presence of primary or secondary alcohols, or aldehydes.[9]
Alternative reagents:
In oxidations of alcohols or aldehydes into carboxylic acids, chromic acid is one of several reagents, including several that are catalytic.
For example, nickel(II) salts catalyze oxidations by bleach (hypochlorite).
Aldehydes are relatively easily oxidised to carboxylic acids, and mild oxidising agents are sufficient.
Silver(I) compounds have been used for this purpose.
Each oxidant offers advantages and disadvantages.
Instead of using chemical oxidants, electrochemical oxidation is often possible.
Handling and Storage of Chromic acid:
Store containers upright & tightly closed in a dry and well-ventilated place.
Containers holding chromic acid and dichromates need to be stored below eye level.
Each container’s label should include a skull-and-crossbones pictogram, the word “Danger”, and identify Chromic acid as both acutely toxic and carcinogenic.
Containers of chromic acid and dichromate salts must be stored in leak-proof secondary containment within a Designated Area.
The secondary container’s label should include a skull-and-crossbones pictogram, the word “Danger”, and identify Chromic acid as both acutely toxic and carcinogenic.
Incompatibles: acids, bases, powdered metals, hydrazine, phosphorous, and all organic chemicals.
Storage Conditions:
Storage site should be as close as practical to lab in which carcinogens are to be used, so that only small quantities required for expt need to be carried.
Carcinogens should be kept in only one section of cupboard, an explosion-proof refrigerator or freezer (depending on chemicophysical properties) that bears appropriate label.
An inventory should be kept, showing quantity of carcinogen & date Chromic acid was acquired.
Facilities for dispensing should be contiguous to storage area.
Reactivity Profile of Chromic acid:
Chromic acid reacts rapidly with many materials including common combustibles, often causing ignition.
Mixing with reducing reagents can cause explosions.
Dangerously reactive with acetone, alcohols, alkali metals (sodium, potassium), ammonia, arsenic, dimethylformamide, hydrogen sulfide, phosphorus, peroxyformic acid, pyridine, selenium, sulfur, and many other chemicals.
Often mixed with sulfuric acid and used to clean glass (“cleaning solution”).
Closed containers for used cleaning solution may explode from the internal pressure of carbon dioxide generated by oxidation of carbon compounds removed from the glass.
Safety of Chromic acid:
Hexavalent chromium compounds (including chromium trioxide, chromic acids, chromates, chlorochromates) are toxic and carcinogenic.
For this reason, chromic acid oxidation is not used on an industrial scale except in the aerospace industry.
Chromium trioxide and chromic acids are strong oxidisers and may react violently if mixed with easily oxidisable organic substances.
Fires or explosions may result.
Chromic acid burns are treated with a dilute sodium thiosulfate solution.
First Aid Measures of Chromic acid:
Call 911 or emergency medical service.
Ensure that medical personnel are aware of Chromic acid(s) involved and take precautions to protect themselves.
Move victim to fresh air if Chromic acid can be done safely.
Give artificial respiration if victim is not breathing.
Do not perform mouth-to-mouth resuscitation if victim ingested or inhaled Chromic acid; wash face and mouth before giving artificial respiration.
Use a pocket mask equipped with a one-way valve or other proper respiratory medical device.
Administer oxygen if breathing is difficult.
Remove and isolate contaminated clothing and shoes.
In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes.
For minor skin contact, avoid spreading material on unaffected skin.
Keep victim calm and warm.
Effects of exposure (inhalation, ingestion or skin contact) to substance may be delayed.
Skin Contact:
Immediately remove contaminated clothing and accessories; flush the skin with water for at least 15 minutes.
Seek medical attention immediately.
Eye Contact:
Check for and remove contact lenses.
Immediately flush eyes with water for at least 15 minutes.
Seek medical attention immediately.
Inhalation:
Move affected individual(s) into fresh air.
Seek medical attention immediately.
Ingestion:
Do not induce vomiting or give anything by mouth to an unconscious person.
Rinse mouth with water.
Seek medical attention.
Isolation and Evacuation:
IMMEDIATE PRECAUTIONARY MEASURE:
Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids.
SPILL:
Increase the immediate precautionary measure distance, in the downwind direction, as necessary.
FIRE:
If tank, rail car or tank truck is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2020)
Firefighting Measures of Chromic acid:
SMALL FIRE:
Dry chemical, CO2 or water spray.
LARGE FIRE:
Dry chemical, CO2, alcohol-resistant foam or water spray.
If Chromic acid can be done safely, move undamaged containers away from the area around the fire.
Dike runoff from fire control for later disposal.
FIRE INVOLVING TANKS OR CAR/TRAILER LOADS:
Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles.
Do not get water inside containers.
Cool containers with flooding quantities of water until well after fire is out.
Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank.
ALWAYS stay away from tanks engulfed in fire.
Non-Fire Response:
ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area.
Do not touch damaged containers or spilled material unless wearing appropriate protective clothing.
Stop leak if you can do Chromic acid without risk.
Prevent entry into waterways, sewers, basements or confined areas.
Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers.
DO NOT GET WATER INSIDE CONTAINERS.
Protective Clothing:
Wear positive pressure self-contained breathing apparatus (SCBA).
Wear chemical protective clothing that is specifically recommended by the manufacturer when there is NO RISK OF FIRE.
Structural firefighters’ protective clothing provides thermal protection but only limited chemical protection.
Disposal Methods of Chromic acid:
Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number D007, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste.
The following wastewater treatment technologies have been investigated for chromic acid:
Concentration process: Reverse Osmosis.
SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations.
Concentrations shall be lower than applicable environmental discharge or disposal criteria.
Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that “pass through” violations will not occur.
Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal.
If Chromic acid is not practicable to manage the chemical in this fashion, Chromic acid must be evaluated in accordance with EPA 40 CFR Part 261, specifically Subpart B, in order to determine the appropriate local, state and federal requirements for disposal.
PRECAUTIONS FOR “CARCINOGENS”: There is no universal method of disposal that has been proved satisfactory for all carcinogenic compounds & specific methods of chem destruction published have not been tested on all kinds of carcinogen-containing waste.
Preventive Measures of Chromic acid:
If employees’ clothing may have become contaminated with solids or liquids containing chromic acid or chromates, employees should change into uncontaminated clothing before leaving the work premises.
Clothing contaminated with chromic acid or chromates should be placed in closed containers for storage until Chromic acid can be discarded or until provision is made for the removal of substance from the clothing. If the clothing is to be laundered or otherwise cleaned to remove the chromic acid or chromates, the person performing the operation should be informed of chromic acid or chromates hazardous properties.
Where there is any possibility of exposure of an employee’s body to solids or liquids containing chromic acid or chromates, facilities for quick drenching of the body should be provided within the immediate work area for emergency use.
Non-impervious clothing which becomes contaminated with chromic acid or chromates should be removed immediately and not reworn until Chromic acid is removed from the clothing.
Identifiers of Chromic acid:
CAS Number: 7738-94-5
ChEBI: CHEBI:33143
ChemSpider: 22834
ECHA InfoCard: 100.028.910
EC Number: 231-801-5
Gmelin Reference: 25982
PubChem CID: 24425
UNII: SA8VOV0V7Q
UN number: 1755 1463
CompTox Dashboard (EPA): DTXSID8034455
InChI: InChI=1S/Cr.2H2O.2O/h;2*1H2;;/q+2;;;;/p-2
Key: KRVSOGSZCMJSLX-UHFFFAOYSA-L check
InChI=1/Cr.2H2O.2O/h;2*1H2;;/q+2;;;;/p-2/rCrH2O4/c2-1(3,4)5/h2-3H
Key: KRVSOGSZCMJSLX-OOUCQFSRAZ
SMILES:
O[Cr](O)(=O)=O
O=[Cr](=O)(O)O
Properties of Chromic acid:
Chemical formula: Chromic acid: H2CrO4
Dichromic acid: H2Cr2O7
Appearance: Dark red crystals
Density: 1.201 g cm−3
Melting point: 197 °C (387 °F; 470 K)
Boiling point: 250 °C (482 °F; 523 K) (decomposes)
Solubility in water: 169 g/100 mL
Acidity (pKa): -0.8 to 1.6
Conjugate base: Chromate and dichromate
Molecular Weight: 118.010 g/mol
Hydrogen Bond Donor Count: 2
Hydrogen Bond Acceptor Count: 4
Rotatable Bond Count: 0
Exact Mass: 117.935813 g/mol
Monoisotopic Mass: 117.935813 g/mol
Topological Polar Surface Area: 74.6Ų
Heavy Atom Count: 5
Complexity: 81.3
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes
Related Products of Chromic acid:
Diphenyltin Dichloride
Dipotassium Hydrogen Phosphite
1,1′-Diisooctyl Ester 2,2′-[(Dioctylstannylene)bis(thio)]bis-acetic Acid (Technical Grade)
Diphenylsilane-D2
4-ethynyl-α,α-diphenyl-Benzenemethanol
Names of Chromic acid:
IUPAC names:
Chromic acid
Dichromic acid
Systematic IUPAC name:
Dihydroxidodioxidochromium
Other names:
Chromic(VI) acid
Tetraoxochromic acid