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EC / List no.: 231-906-6
CAS no.: 7778-50-9
Mol. formula: Cr2H2O7.2K
Potassium Bichromate, K2Cr2O7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications.
As with all hexavalent chromium compounds, Potassium Bichromate is acutely and chronically harmful to health.
Potassium Bichromate is a crystalline ionic solid with a very bright, red-orange color.
The salt is popular in the laboratory because Potassium Bichromate is not deliquescent, in contrast to the more industrially relevant salt sodium dichromate.
Description: Soluble in water, and insoluble in alcohol.
Appearance: Orange yellow crystals.
Quality
K2Cr2O7 ≧ 99.7%
SO4 ≦ 0.05%
Cl ≦ 0.07%
Insolubles ≦ 0.05%
Na ≦ 0.5%
Applications: Inorganic pigments, dyestuffs/stain, oxidizing agents, firelighter →Mordant for dyeing,Dyestuffs,Tanning of leather,Pigments,Pyrotechnics,Explosives,Pharmaceutical preparation,Oxidizing agent in organic syntheses,Catalysts
Orange red crystals
Denser than water and soluble in water.
No distinctive odor.
May severely irritate the eyes and respiratory tract.
Avoid contact with organic materials. Noncombustible. Used in pyrotehnic displays with tungsten and iron.
Chemistry
Production
Potassium Bichromate is usually prepared by the reaction of potassium chloride on sodium dichromate. Alternatively, Potassium Bichromate can be also obtained from potassium chromate by roasting chromite ore with potassium hydroxide.
Reactions
Potassium Bichromate is an oxidising agent in organic chemistry, and is milder than potassium permanganate.
Potassium Bichromate is used to oxidize alcohols.
Potassium Bichromate converts primary alcohols into aldehydes and, under more forcing conditions, into carboxylic acids.
In contrast, potassium permanganate tends to give carboxylic acids as the sole products.
Secondary alcohols are converted into ketones. For example, menthone may be prepared by oxidation of menthol with acidified dichromate.
Tertiary alcohols cannot be oxidized.
In an aqueous solution the color change exhibited can be used to test for distinguishing aldehydes from ketones.
Aldehydes reduce dichromate from the +6 to the +3 oxidation state, changing color from orange to green.
This color change arises because the aldehyde can be oxidized to the corresponding carboxylic acid.
A ketone will show no such change because it cannot be oxidized further, and so the solution will remain orange.
When heated strongly, it decomposes with the evolution of oxygen.
4 K2Cr2O7 → 4 K2CrO4 + 2 Cr2O3 + 3 O2
When an alkali is added to an orange-red solution containing dichromate ions, a yellow solution is obtained due to the formation of chromate ions (CrO2−4).
For example, potassium chromate is produced industrially using potash:
K2Cr2O7 + K2CO3 → 2 K2CrO4 + CO2
The reaction is reversible.
Treatment with cold sulfuric acid gives red crystals of chromic anhydride (chromium trioxide, CrO3):
K2Cr2O7 + 2 H2SO4 → 2 CrO3 + 2 KHSO4 + H2O
On heating with concentrated acid, oxygen is evolved:
2 K2Cr2O7 + 8 H2SO4 → 2 K2SO4 + 2 Cr2(SO4)3 + 8 H2O + 3 O2
Uses:
Potassium Bichromate has few major applications, as the sodium salt is dominant industrially.
The main use is as a precursor to potassium chrome alum, used in leather tanning.
Cleaning
Like other chromium(VI) compounds (chromium trioxide, sodium dichromate), Potassium Bichromate has been used to prepare "chromic acid" for cleaning glassware and etching materials.
Because of safety concerns associated with hexavalent chromium, this practice has been largely discontinued.
Construction
Potassium Bichromate is used as an ingredient in cement in which it retards the setting of the mixture and improves its density and texture.
This usage commonly causes contact dermatitis in construction workers.
Photography and printing
In 1839, Mungo Ponton discovered that paper treated with a solution of Potassium Bichromate was visibly tanned by exposure to sunlight, the discoloration remaining after the Potassium Bichromate had been rinsed out.
In 1852, Henry Fox Talbot discovered that exposure to ultraviolet light in the presence of Potassium Bichromate hardened organic colloids such as gelatin and gum arabic, making them less soluble.
These discoveries soon led to the carbon print, gum bichromate, and other photographic printing processes based on differential hardening.
Typically, after exposure, the unhardened portion was rinsed away with warm water, leaving a thin relief that either contained a pigment included during manufacture or was subsequently stained with a dye.
Some processes depended on the hardening only, in combination with the differential absorption of certain dyes by the hardened or unhardened areas.
Because some of these processes allowed the use of highly stable dyes and pigments, such as carbon black, prints with an extremely high degree of archival permanence and resistance to fading from prolonged exposure to light could be produced.
Dichromated colloids were also used as photoresists in various industrial applications, most widely in the creation of metal printing plates for use in photomechanical printing processes.
Chromium intensification or Photochromos uses Potassium Bichromate together with equal parts of concentrated hydrochloric acid diluted down to approximately 10% v/v to treat weak and thin negatives of black and white photograph roll.
This solution reconverts the elemental silver particles in the film to silver chloride.
After thorough washing and exposure to actinic light, the film can be redeveloped to its end-point yielding a stronger negative which is able to produce a more satisfactory print.
A Potassium Bichromate solution in sulfuric acid can be used to produce a reversal negative (that is, a positive transparency from a negative film).
This is effected by developing a black and white film but allowing the development to proceed more or less to the end point.
The development is then stopped by copious washing and the film then treated in the acid dichromate solution.
This converts the silver metal to silver sulfate, a compound that is insensitive to light.
After thorough washing and exposure to actinic light, the film is developed again allowing the previously unexposed silver halide to be reduced to silver metal.
The results obtained can be unpredictable, but sometimes excellent results are obtained producing images that would otherwise be unobtainable.
This process can be coupled with solarisation so that the end product resembles a negative and is suitable for printing in the normal way.
Cr(VI) compounds have the property of tanning animal proteins when exposed to strong light.
This quality is used in photographic screen-printing.
In screen-printing a fine screen of bolting silk or similar material is stretched taut onto a frame similar to the way canvas is prepared before painting.
A colloid sensitized with a dichromate is applied evenly to the taut screen.
Once the dichromate mixture is dry, a full-size photographic positive is attached securely onto the surface of the screen, and the whole assembly exposed to strong light – times vary from 3 minutes to a half an hour in bright sunlight – hardening the exposed colloid.
When the positive is removed, the unexposed mixture on the screen can be washed off with warm water, leaving the hardened mixture intact, acting as a precise mask of the desired pattern, which can then be printed with the usual screen-printing process.
Analytical reagent
Because it is non-hygroscopic, Potassium Bichromate is a common reagent in classical "wet tests" in analytical chemistry.
Ethanol determination
The concentration of ethanol in a sample can be determined by back titration with acidified Potassium Bichromate.
Reacting the sample with an excess of Potassium Bichromate, all ethanol is oxidized to acetic acid:
CH3CH2OH + 2[O] → CH3COOH + H2O
Full reaction of converting ethanol to acetic acid:
3 C2H5OH + 2 K2Cr2O7 + 8 H2SO4 → 3 CH3COOH + 2 Cr2(SO4)3 + 2 K2SO4 + 11 H2O
The excess dichromate is not determined by titration against sodium thiosulfate.
Adding the amount of excess dichromate from the initial amount, gives the amount of ethanol present.
Accuracy can be improved by calibrating the dichromate solution against a blank.
One major application for this reaction is in old police breathalyzer tests.
When alcohol vapor makes contact with the orange dichromate-coated crystals, the color changes from Cr(VI) orange to Cr(III) green.
The degree of the color change is directly related to the level of alcohol in the suspect's breath.
Silver test
When dissolved in an approximately 35% nitric acid solution it is called Schwerter's solution and is used to test for the presence of various metals, notably for determination of silver purity.
Pure silver will turn the solution bright red, sterling silver will turn it dark red, low grade coin silver (0.800 fine) will turn brown (largely due to the presence of copper which turns the solution brown) and even green for 0.500 silver.
Brass turns dark brown, copper turns brown, lead and tin both turn yellow while gold and palladium do not change.
Sulfur dioxide test
Potassium Bichromate paper can be used to test for sulfur dioxide, as it turns distinctively from orange to green.
This is typical of all redox reactions where hexavalent chromium is reduced to trivalent chromium.
Therefore, it is not a conclusive test for sulfur dioxide.
The final product formed is Cr2(SO4)3.
Wood treatment
Potassium Bichromate is used to stain certain types of wood by darkening the tannins in the wood.
Potassium Bichromate produces deep, rich browns that cannot be achieved with modern color dyes.
Potassium Bichromate is a particularly effective treatment on mahogany.
Natural occurrence
Potassium Bichromate occurs naturally as the rare mineral lopezite.
Potassium Bichromate has only been reported as vug fillings in the nitrate deposits of the Atacama desert of Chile and in the Bushveld igneous complex of South Africa.
About Potassium Bichromate
Helpful information
Potassium Bichromate is registered under the REACH Regulation and is manufactured in and / or imported to the European Economic Area, at ≥ 100 to < 1 000 tonnes per annum.
Potassium Bichromate is used by professional workers (widespread uses), in formulation or re-packing, at industrial sites and in manufacturing.
Consumer Uses
ECHA has no public registered data indicating whether or in which chemical products the substance might be used.
ECHA has no public registered data on the routes by which Potassium Bichromate is most likely to be released to the environment.
Article service life
ECHA has no public registered data on the routes by which Potassium Bichromate is most likely to be released to the environment.
ECHA has no public registered data indicating whether or into which articles the substance might have been processed.
Widespread uses by professional workers
Potassium Bichromate is used in the following products: laboratory chemicals and pH regulators and water treatment products.
Potassium Bichromate has an industrial use resulting in manufacture of another substance (use of intermediates).
Potassium Bichromate is used in the following areas: scientific research and development.
Release to the environment of Potassium Bichromate can occur from industrial use: formulation of mixtures, as an intermediate step in further manufacturing of another substance (use of intermediates) and as processing aid.
Other release to the environment of Potassium Bichromate is likely to occur from: indoor use as reactive substance.
Formulation or re-packing
Potassium Bichromate is used in the following products: metal surface treatment products, laboratory chemicals, metals, non-metal-surface treatment products and pH regulators and water treatment products.
Potassium Bichromate has an industrial use resulting in manufacture of another substance (use of intermediates).
Release to the environment of Potassium Bichromate can occur from industrial use: formulation of mixtures, manufacturing of the substance, formulation in materials, in processing aids at industrial sites, as an intermediate step in further manufacturing of another substance (use of intermediates), as processing aid, of substances in closed systems with minimal release and in the production of articles.
Uses at industrial sites
Potassium Bichromate is used in the following products: metal surface treatment products, pharmaceuticals, textile treatment products and dyes and laboratory chemicals.
Potassium Bichromate has an industrial use resulting in manufacture of another substance (use of intermediates).
Potassium Bichromate is used in the following areas: formulation of mixtures and/or re-packaging.
Potassium Bichromate is used for the manufacture of: chemicals, machinery and vehicles, metals and fabricated metal products.
Release to the environment of Potassium Bichromate can occur from industrial use: in the production of articles, as an intermediate step in further manufacturing of another substance (use of intermediates), as processing aid, of substances in closed systems with minimal release, in processing aids at industrial sites, formulation of mixtures and manufacturing of the substance.
Manufacture
Release to the environment of Potassium Bichromate can occur from industrial use: manufacturing of the substance, formulation of mixtures, as an intermediate step in further manufacturing of another substance (use of intermediates), of substances in closed systems with minimal release, formulation in materials, in processing aids at industrial sites, as processing aid and in the production of articles.
General description
Potassium Bichromate (Formula K2Cr2O7) will be decomposed and releases oxygen under the white heat temperature.
Potassium Bichromate has strong oxidizing property, being a strongly toxic and carcinogenic oxidant.
Potassium Bichromate appears as orange-red solid at room temperature and plate crystal.
Potassium Bichromate has been classified as a Category I carcinogen by the International Agency for Research on Cancer (IARC), and may be combustible when come into contact with combustibles.
At temperature above 500 ° C, Potassium Bichromate can lead to oxidation to generate chromic acid and chromium oxide.
Potassium Bichromate has very small solubility at low temperature and does not contain crystal water.
Potassium Bichromate is easily purified through recrystallization; also not easy to have deliquescence and thus often being used as the reference standard in the analysis.
Owing to the strong oxidizing properties of Potassium Bichromate under acidic conditions, Potassium Bichromate is commonly used in the laboratory to formulate a chromic acid washing agent (a mixture of saturated Potassium Bichromate solution and concentrated sulfuric acid) for washing the chemical glassware in order to remove the reductive dirt in the glass wall.
After use, the washing agent changes from dark red to green color under which the washing agent becomes invalid.
Potassium Bichromate can also used be in analytical chemistry, commonly used to determine the reductive hydrogen sulfide, sulfurous acid, ferrous ions and so on.
Upon the heating, Potassium Bichromate can also oxidize concentrated hydrochloric acid to release chlorine.
As the raw materials for the production of leather hydrolysates are mainly from the corner of the tannery factory waste, and these wastes often contain Potassium Bichromate and sodium dichromate, during the production of hydrolyzed protein, Potassium Bichromate, sodium dichromate will be naturally brought into the dairy products.
Human drinking can lead to joint osteoporosis, swelling and other poisoning problems.
Chroming workers subjecting to repeated or long-term exposure to low concentrations of chromium compounds can get chronic upper respiratory tract inflammation, chrome rhinopathy, contact dermatitis and rash which mainly occur in naked places such as the face, neck, hands and forearm.
Potassium Bichromate can also cause kidney and liver damage as well as causing blood system changes.
The occurrence of lung cancer has a incubation period of 10-20 years.
Defination
Potassium bichromate is an odorless substance that can be found naturally occurring in the environment, for instance, in ash, sand, loam, and clay.
The chemical occurs in steel-made tools, and chrome-plated objects such as needles, silverware, handles, and bracelets.
Furthermore, Potassium Bichromate is used as a component of fur-tanning agents, leather, dark textile dyes, epoxy hardeners, chromium pigments, and photographic color developer.
The orange-red color powdered substance has a melting point of 398oC and a molecular weight of 294 gram (g)/mol. Notably, the chemical is soluble in water and ethyl alcohol.
Production
The production of potassium bichromate begins with the reaction of chromium trioxide and potassium hydroxide in a reactor generating a mother liquor.
2 CrO3 + 2 KOH = K2Cr2O7 + H2O
The next step is filtration of the mother liquor and the ensuing filter solids are put aside for disposal.
The remaining substance is then sent for precipitation of crystalline potassium bichromate through a centrifugation process.
Finally, the mother liquor from the centrifuge is sent back to the reactor.
Application Potassium bichromate is an inorganic oxidizing agent that has multiple scientific and industrial uses.
Photography
Potassium bichromate has significant uses in photographic screen-printing and photography where together with strong mineral acid, they can be used as an oxidizing agent.
In the 1850s, gum bichromate printing was largely used in the photographic printing processes.
Potassium Bichromate is worth noting that when exposed to ultraviolet light, a solution of potassium bichromate and gum Arabic will be dried and hardened.
Together with concentrated hydrochloric acid (HCL), photochromos and chromium uses potassium bichromate to treat thin and weak negatives of black and white photograph roll.
The solution of HCL together with potassium bichromate reconverts the particles of silver in the film to silver chloride.
The film is the exposed to actinic light and then redeveloped to its end product, giving out a more stronger negative and a acceptable print.
In sulfuric acid, potassium bichromate solution can be used to manufacture a reversal negative.
Industrial Uses
Manufacturers in the textile industry use the chemical in dying clothe fabrics and tanning leather.
In addition, potassium bichromate is normally used in decorative chromium plating as well as coating active metals such as steel and aluminum to prevent them from corrosion.
In science, the substance is used as a solvent and in the identification of certain elements in solutions.
In the furniture industry, the chemical is used in straining wood.
Chemical Properties
Also known as potassium bichromate and red potassium chromate, K2Cr2O7 is poisonous,yellowish-red crystals with a metallic taste that is soluble in water,insoluble in alcohol,that melt at 396℃ ;and decompose at 500℃.
Used as an oxidizing agent and analytical reagent,and in explosives, matches, and electroplating.
Potassium chromate(VI) is a yellow crystalline solid.
Uses:
Potassium bichromate is also known as Potassium Bichromate, this bright orange crystal was made by the acidification of potassium chromate.
Potassium Bichromate is toxic and an oxidant and is soluble in water but not in alcohol.
In 1839 Mungo Ponton sensitized paper with a solution of potassium bichromate to print-out images in the sun.
The most important use of potassium bichromate was used to make colloids sensitive to light for a variety of processes such as the photoglyphic engraving process, the carbon process, the gum bichromate process, and in the preparation of the gelatin relief used to make lead molds for the Woodburytype.
Potassium Bichromate uses in matches,
Potassium Bichromate uses in leather tanning and in the textile industry,
Potassium Bichromate uses as a source of chromate,
Potassium Bichromate uses in pyrotechnics,
Potassium Bichromate uses in colored glass,
Potassium Bichromate uses as an important laboratory reagent,
Potassium Bichromate uses in blueprint developing, and
Potassium Bichromate uses in wood preservation formulations.
Potassium Bichromate uses In tanning leather, dyeing, painting, decorating porcelain, printing, photolithography, pigment-prints, staining wood, pyrotechnics, safety matches, for bleaching palm oil, wax, and sponges, waterproofing fabrics, as oxidizer in the manufacture of organic chemicals, in electric batteries, as depolarizer for dry cells.
As corrosion inhibitor in preference to sodium dichromate where lower soly is advantageous. Pharmaceutic aid (oxidizing agent).
Definition
ChEBI: A potassium salt that is the dipotassium salt of dichromic acid.
General Description
Orange red crystals.
Denser than water and soluble in water.
No distinctive odor.
May severely irritate the eyes and respiratory tract.
Avoid contact with organic materials. Noncombustible.
Used in pyrotehnic displays with tungsten and iron.
Air & Water Reactions
Soluble in water.
Where is Potassium Bichromate found?
Potassium Bichromate is found naturally in our environment; in sand, ash, clay, and loam.
Potassium Bichromate can be found in tools made of steel, and chrome-plated objects (silverware, handles, bracelets, needles, etc.).
Chromium is also used as a component in leather (shoes, suede, upholstery) and fur tanning agents, wood preservatives, anti-corrosion paints, fire retardants, printing inks, color glazes, chromium pigments, dark textile dyes, concrete, epoxy hardeners, and photographic color developer.
Chromate is also found in cement (not dried) and metal plating and is a cause of occupational dermatitis in bricklayers, construction workers, and metal workers.
Potassium Bichromate is known by many names such as Potassium bichromate, bichromate of potash, dipotassium dichromate or as formula K2Cr2O7.
Potassium Bichromate is in our stock in the Netherlands. We are successfully exporting this product, as metal surface treatment to aerospace an defence industry world-wide.
Product information
Potassium bichromate(VI) is a fine, bright red crystalline.
As a result of its oxidizing properties, it can be used as an oxidizer in a variety of industries.
Examples are cleaning-, metal surface- and safety-match producers or as printing images in photography.
Potassium Bichromate is most often used as an oxidizing agent in laboratories and industries.
Potassium Bichromate is used as a precursor to prepare potassium chrome alum which finds application in leather finishing and tanning.
Potassium Bichromate is utilized in the preparation of chromic acid for cleaning glassware and etching materials.
Potassium Bichromate is an active ingredient in cement used for retards setting and improves its density and texture. Furthermore, it is used in photography and in photographic screen printing.
Potassium Bichromate is also used in wet test analysis as an analytical lab reagent and in ethanol determination.
Potassium Bichromate has important uses in photography, it is a common inorganic chemical reagent.
IUPAC NAMES:
dipotassium [(oxidodioxochromio)oxy]chromiumoylolate
DiPotassium Bichromate
DiPotassium Bichromate
diPotassium Bichromate
dipotassium oxido-(oxido(dioxo)chromio)oxy-dioxochromium
dipotassium;oxido-(oxido(dioxo)chromio)oxy-dioxochromium
Potassium Bichromate
Potassium dichromate
potassium dichromate
Potassium Dichromate
Potassium dichromate
potassium dichromate
potassium dichromate (VI)
Potassium dichromate(VI)
potassium dichromate(VI)
PotassiumDichromate
potassiumdichromate
sodium dichromate
SYNONYMS:
bichromateofpotash
chromicacid(h2cr2o7),dipotassiumsalt
chromicacid,dipotassiumsalt
chromicacid[h2cr2o7],dipotassiumsalt
dichromatedepotassium
Dichromicacid,dipotassiumsalt
dichromicacid[h2cr2o7],dipotassiumsalt
dichromicaciddipotassiumsalt
dipotassiumbichromate
dipotassiumdichromate
iopezite
kaliumdichromat
potassiumdichromate(vi)
potassiumdichromate[k2(cr2o7)]
potassiumdichromate6
Redpotassiumchromate
ELECTROLYTIC CHROMIUM
CHROMIUM STANDARD
CHROMIUM STANDARD SOLUTION
CHROMIUM SINGLE ELEMENT PLASMA STANDARD
CHROMIUM SINGLE ELEMENT STANDARD
CHROMIUM METAL
CHROMIUM METALLO-ORGANIC STANDARD
CHROMIUM PLASMA EMISSION SPECTROSCOPY STANDARD
CHROMIUM PLASMA EMISSION STANDARD
CHROMIUM, PLASMA STANDARD SOLUTION
CHROMIUM POWDER
CHROMIUM, OIL BASED STANDARD SOLUTION
CHROMIUM, ORGANIC AAS STANDARD SOLUTION
CHROMIUM ATOMIC ABSORPTION STANDARD
CHROMIUM ICP STANDARD
CHROMIUM(III) AA/ICP CALIBRATION/CHECK STANDARD
CHROMIUM AA SINGLE ELEMENT STANDARD
CHROMIUM, AAS STANDARD SOLUTION
CHROMIUM AA STANDARD
CHROMIUM AA STANDARD CONCENTRATE
Potassiumdichromate,99%
Potassium dichromate, 4 wt% solution in water, pure
Potassium dichromate, extra pure, 99.50%
Potassium dichromate, for analysis ACS, 99+%
Potassium dichromate, for analysis, 99.5%
POTASSIUM DICHROMATE CERTIFIED
POTASSIUM DICHROMATE REAGENT (ACS)
POTASSIUM DICHROMATE, 0.025 N SOLUTION
POTASSIUM DICHROMATE, 0.1 N SOLUTION
POTASSIUM DICHROMATE, 0.5 N SOLUTION
Potassiumdichromate,99+%(ACS)
potassium dichromate solution
potassium dichromate, primary standard, acs
POTASSIUMDICHROMATE,CRYSTAL,REAGENT,ACS
POTASSIUMDICHROMATE,CRYSTAL,REAGENTSPECIAL,ACS
POTASSIUMDICHROMATE,GRANULAR,TECHNICAL
POTASSIUMDICHROMATE,TECHNICAL(BULK
Potassium Dichromate, Acs Grade
Potassium dichromate, Acculute Standard Volumetric Solution, Final Concentration 0.1N
Potassium dichromate, primary standard, ACS, 99.0% min
Potassium dichromate, 0.025N Standardized Solution
Potassium dichromate, 0.25N Standardized Solution
