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Chromium binds to the stainless steel surface and protects it from acid-causing rust that is contained in many types of food.

Source
Americankitchencookware.com 1/4
Not a lot of information. A lot of ads. Not organized.

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If you've spent any time shopping for cookware, you've likely run across an 18/10 stainless steel label. At American Kitchen Cookware, we are proud that our tri-ply stainless steel construction includes a layer of 18/10 stainless steel. But what does it mean? 18 points out of 10 sounds extraordinary! We think our products are exceptional, but let's clear up this quandary and understand what is behind those numbers.

What is 18/10 (18/8 and 18/0) Stainless Steel?

18/10 stainless steel, as well as 18/8 and 18/0, are fractions explaining the percentages of chromium and nickel alloys, respectively, added to stainless steel to reduce rust and enhance shine and durability. 18/0 contains limited nickel and is therefore, slightly less resistant to oxidation, while 18/10 provides the highest amount of nickel producing the greatest resistance to rust, and longest held polish.

Why does 18/10 Stainless Steel Matter in Cookware?

As stated above, 18 and 10 are the percentages of chromium and nickel alloys that are added to stainless steel cookware to enhance performance. But what do they do? Chromium binds to the stainless steel surface and protects it from acid-causing rust that is contained in many types of food. Nickel, meanwhile, prevents corrosion while adding luster on the steel's surface.

Stainless steel alone doesn't provide optimal heating, so alloys are necessary to produce the best cookware. The 18/10 mix combined with American Kitchen's tri-ply construction (an 18/10 stainless steel interior with an aluminum core and magnetic stainless steel exterior), results in an even distribution of heat across the cookware while your food remains protected from a reaction with the aluminum.

The result of that little bit of chemistry is durable, easy-to-clean, rust-resistant cookware!

At American Kitchen Cookware we are proud of to offer 18/10 stainless steel cookware sets and individual products, so that you can cook with confidence. Once you've tasted the benefits of our meticulously crafted tri-ply construction, you'll understand why 18/10 is exceptional in our (cook) book!

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If you've spent any time shopping for cookware, you've likely run across an 18/10 stainless steel label. At American Kitchen Cookware, we are proud that our tri-ply stainless steel construction includes a layer of 18/10 stainless steel. But what does it mean? 18 points out of 10 sounds extraordinary!

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Chromium dipped fishing line floats in the water and is strong as strong gets. Light as a feather.

Source
Colvilleoutfitters.com 3/4
Lots of info on it. No ads at all. Well organized.

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Description

Chromium Float Line 5 Different Lbs, All Smoke Color, All 300 Yards, All $29.99 So if you want to drop down box for 5? "Chromium Float Centerpin Main Line" Exclusively Designed For Colville Outfitters, State of the art camouflage design, lowest stretch currently on the market today, Incredible abrasion resistant, superior knot strength, superlight design allows for easy mending and solid hook sets on super hero drifts and line will not absorb water and become saturated during those long days spent fishing.

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Hitena Float Chromium Line - Colville Outfitters

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Chromium Float Line 5 Different Lbs, All Smoke Color, All 300 Yards, All $29.99 So if you want to drop down box for 5?

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Chromium also oxidizes, but unlike iron, the oxides of chromium are very hard.

Source
Archive.boston.com 2/4
A lot of information. A lot of unnecessary info. A couple ads on the side.

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The key to understanding chromium coating and how it protects steel lies in understanding the nature of rust. Rust is a combination of various oxides of iron and water, which arise when the iron in steel is exposed to oxygen and water. The main reason rust is a problem is that it's mechanically quite fragile. It easily flakes off or breaks, exposing the metal below so that it, too, can turn to rust. Eventually, an unprotected steel or iron object just rusts away.

Chromium also oxidizes, but unlike iron, the oxides of chromium are very hard. A chromium coating rapidly gets a very thin layer of very hard chromium oxide (the chromium version of rust), which protects the surface from further damage.

A similar phenomenon happens with aluminum. If you file a piece of aluminum, you can expose the shiny metal underneath the oxide. With time it will oxidize to the dull color of aluminum you are more used to seeing, forming a protective layer again.

Chromium's oxidation layer is so shallow that it is transparent and you see what looks like unoxidized metal.

Chromium is also an ingredient in so-called stainless steels, which are made with at least 11 percent chromium by weight. These steels are also protected from corrosion by a thin layer of chromium oxide on the surface - good enough coverage, despite not being pure chromium, that the iron component of the metal does not rust.
Ask Dr. Knowledge is written by a physicist at Northeastern University, John Swain. E-mail questions to drknowledge@globe.com or write to Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819.

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What makes chromium good for protecting car bumpers?

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The key to understanding chromium coating and how it protects steel lies in understanding the nature of rust. Rust is a combination of various oxides of iron and water, which arise when the iron in steel is exposed to oxygen and water. The main reason rust is a problem is that it's mechanically quite fragile.

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Of the lead materials used for bike frames, ranging from aluminum to titanium and even carbon fiber, Chromoly offers the best cost-benefit ratio.

Source
Detroitbikes.com 3/4
Lots of information. Nicely organized. Lots of different types of frames on there.

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More bikes are made out of steel than any other material, but not all steel is created equal. Our bicycles at Detroit Bikes are made out of American chromium molybdenum steel, commonly known as Chromoly. Chromoly is a chrome-alloy steel with a medium carbon content and .8% - 1.1% molybdenum for strength. It is a steel that is stronger than carbon steel (more commonly used in bike manufacturing), so we can use thin wall tubing, giving you a lightweight frame that will last through years of riding.

Of the lead materials used for bike frames, ranging from aluminum to titanium and even carbon fiber, Chromoly offers the best cost-benefit ratio.

Chromoly vs Aluminum

Aluminum is the second most commonly used material for bicycle manufacturing. It's lighter and stiffer than steel, but it's also more brittle and easily damaged. Chromoly is slightly heavier than aluminum, but the frame can be thinner and has reduced stiffness, which provides a smoother ride.

Steel is ductile, unlike aluminum, which makes it possible to offer stronger seamless steel tubes. Also, steel is reliable: it fails in a predictable way, bending before it breaks. Aluminum, on the other hand, is more like glass, which breaks before it bends.

Chromoly vs Titanium or Carbon Fiber

Far higher in price than steel or aluminum are more exotic materials, such as titanium and carbon fiber. These are great materials for bicycles, offering their own advantages. We choose high-quality steel because it offers the best bang for your buck when it comes to leading quality options. Titanium has been used for several decades now. Its strength is comparable to steel, but it's lighter. Compared to Chromoly, titanium is not only a more expensive material but also requires a more meticulous manufacturing process because it can be easily contaminated, which results in a significantly more expensive bike.

Carbon fiber is strong and light, but it can be brittle if stressed in the wrong way. This type of material can be easily molded compared to the others, so it's popular for bicycles of unconventional shapes. A high-quality carbon frame bicycle with a high strength to weight ratio costs thousands of dollars.

Made In The U.S.A.

While Chromoly itself is arguably one of the best materials for a bicycle, the way the material is used to create a bike matters, as well. In addition to sourcing our Chromoly steel from US manufacturers, Detroit Bikes produces our USC line of bike frames right in our Detroit factory, where we also paint, assemble, wheel build, and package our products.

If you're looking for a high-quality urban commuter bike, consider one of our Chromoly steel bikes. They're durable and classic, and they provide a wonderful to ride. Even if a Chromoly bike hasn't been on your radar, we encourage you to find a retailer near you to test out the best Chromoly bikes and feel the difference.

Also in The Bike Blog

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More bikes are made out of steel than any other material, but not all steel is created equal. Our bicycles at Detroit Bikes are made out of American chromium molybdenum steel, commonly known as Chromoly. Chromoly is a chrome-alloy steel with a medium carbon content and .8% - 1.1% molybdenum for strength.

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By adding chromium to the steel it increases the resistance to oxidation and corrosion in general.

Source
Knifeinformer.com 2/4
Pretty organized. Lots of information. A few ads came up.

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As an extension of our Guide to the Best Knife Steel, we've compiled the reference table below showing the most popular types of knife steel and their composition of the various elements. You can click on the column to sort the data accordingly.
>>See knives with our favorite premium steel at BladeHQ<<
Below the table you'll find a summary of the most commonly used elements in steel production and their impact on the properties and overall quality of the steel.

Summary of key elements

Here is a useful summary of the alloying elements that are vital in knife production together with a brief description of their impact on the resulting steel's properties.

Carbon (C)

Contributes: Hardness, Edge Retention. You'll find carbon in every form of steel. Essentially, it's the element that turns the basic metal iron into steel and plays a huge part in the hardening process. Generally with increased levels of carbon you get a harder steel, improved tensile strength, edge retention and overall resistance to wear. Knife steels are typically described as "high carbon" if they contain more than 0.5% carbon and these generally what you want to look for in a knife steel. However, if manufacturers go over the top with too much carbon it can make the steel brittle and also increases proneness to corrosion.

Chromium (Cr)

Contributes: Corrosion Resistance. By adding chromium to the steel it increases the resistance to oxidation and corrosion in general. To be classified as "Stainless Steel" there should be at least 13% chromium (you'll see others quote 11% or 12% but 13% is a safe bet). Chromium is the key driver for carbide formation which lowers brittleness but also adversely impacts edge retention. In addition to improving the resistance to corrosion, chromium also improves hardenability and tensile strength. Still, every steel is going to corrode if left out in the elements for a prolonged period. Note also that too much chromium can reduce toughness.

Molybdenum (Mo)

Contributes: Toughness. Molybdenum will increase toughness which reduces the liklihood of chipping. It also allows the steel to maintain its strength at high temperatures which helps with how easy a blade is to produce in the factory. Like chromium it is a driver of carbide formation but is used typically in small relative quantities.

Nickel (Ni)

Contributes: Toughness. Some manufacturers have chosen to add small quantities of Nickel to increase toughness and strength especially at low temperatures which basically limits distortion and cracking during the quenching phase of heat treatment. Many knife makers claim it also reduces corrosion but that is often disputed.

Vanadium (V)

Contributes: Toughness, Wear Resistance. Vanadium is another element similar to Molybdenum that promotes carbide formation (the hardest of all) and it adds wear resisting properties to steels. Perhaps more importantly, vanadium produces a very fine grain during the steel's heat treatment process which improves overall toughness. Some of the ultra-premium steels contain relatively high levels of vanadium and allow for a super sharp edge.

Cobalt (Co)

Contributes: Hardness. Adding very small amounts of cobalt can allow for quenching (i.e. rapid cooling to achieve hardness) at higher temperatures and tends to boost the effects of other elements in the more complicated steels. It is not a carbide former in itself but certainly does promote the achievement of overall hardness.

Manganese (Mn)

Contributes: Hardenability, Strength, Wear Resistance. Another key element which assists with the hot working properties making the knife more stable during quenching. Manganese will contribute to increased hardness as well as tensile strength and resistance to wear and tear. As with anything that increases hardness, too much and the steel will be too brittle.

Silicon (Si)

Contributes: Hardenability, Strength. Silicon adds to overall strength similar to the effects of Manganese, making the manufacture of the steel far more stable. However, the real value of Silicon is in de-oxidation and de-gasifying to remove oxygen. Oxygen is unwelcomed in steel production because it leads to blowholes or pitting.

Niobium (Nb)

Contributes: Toughness, Wear Resistance, Corrosion Resistance. Niobium is a grain refiner and powerful carbide former. It is used to aid fine grain structure which helps to improve the wear resistance and prevent chipping. Arguably the best known knife steel that capitalized on Niobium is CPM-S35VN which combined with carbon, introduced niobium carbides to aid wear resistance and edge chipping. The result is formidable edge retention.

Tungsten (W)

Contributes: Toughness, Wear Resistance . Tungsten forms carbides and will tend to improve resistance to wear and tear. It is usually added in conjunction with chromium or molybdenum for best results.

Sulfur (S)

Contributes: Machinability. Sulfur is often regarded as an impurity in steel. However, in small amounts, Sulfur improves machinability and chip formation. Sulfur additions are made in proportion to Manganese concentration to control the shape of the Manganese/sulfur formation.

Phosphorus (P)

Contributes: Hardness, Corrosion Resistance. Phosphorous is generally considered to be an impurity in steels. It can be found in amounts up to 0.04% in carbon steels. In hardened steels it can create brittleness. In higher-strength, lower-alloy steels phosphorus can be added up to 0.10% for improving strength, hardness and resistance to corrosion.

Nitrogen (N)

Contributes: Corrosion Resistance. Nitrogen can be used in place of carbon in the steel matrix. It increases resistance to localized corrosion, especially in combination with molybdenum. The Nitrogen atom will function in a similar manner to the carbon atom but offers unusual advantages in corrosion resistance.

Copper (Cu)

Contributes: Corrosion Resistance, Hardness. Copper enhances corrosion resistance and may promote precipitation hardening properties. It can be added to lower work-hardening in steels designed for improved machinability and to improve formability.

Other elements used less frequently include Aluminium (Al), Boron (B), Lead (Pb).

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As an extension of our Guide to the Best Knife Steel, we've compiled the reference table below showing the most popular types of knife steel and their composition of the various elements. You can click on the column to sort the data accordingly.

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Calcium chromate is a yellow powder. It is slightly soluble in water. The primary hazard is the threat to the environment.

Source
Cameochemicals.noaa.gov 3/4
Very reliable.
Disorganized site.
No ads popped up.

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Chemical Identifiers | Hazards | Response Recommendations | Physical Properties | Regulatory Information | Alternate Chemical Names

Chemical Identifiers

The Chemical Identifier fields include common identification numbers, the NFPA diamond U.S. Department of Transportation hazard labels, and a general description of the chemical. The information in CAMEO Chemicals comes from a variety of data sources.

Calcium chromate is a yellow powder. It is slightly soluble in water. The primary hazard is the threat to the environment. Immediate steps should be taken to prevent its spread to the environment.

Hazards

Special Hazards of Combustion Products: Toxic chromium fume may be formed in fires.

Behavior in Fire: The hydrated salt loses water when hot and changes color, but no increase in hazard occurs. (USCG, 1999)

Inhalation causes irritation of nose and throat. Ingestion causes severe circulatory collapse and chronic nephritis. Contact with eyes causes irritation. Contact with skin may cause dermatitis and ulcers. (USCG, 1999)

CALCIUM CHROMATE is a strong oxidizer and reacts with acids and ethanol. (NTP, 1992)

Belongs to the Following Reactive Group(s)

Potentially Incompatible Absorbents

Use caution: Liquids with this reactive group classification have been known to react with the absorbents listed below. More info about absorbents, including situations to watch out for...

Cellulose-Based Absorbents

Expanded Polymeric Absorbents

Response Recommendations

The Response Recommendation fields include isolation and evacuation distances, as well as recommendations for firefighting, non-fire response, protective clothing, and first aid. The information in CAMEO Chemicals comes from a variety of data sources.

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]:

As an 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, in the downwind direction, as necessary, the isolation distance shown above.

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, 2016)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]:

SMALL FIRE: Dry chemical, CO2 or water spray.

LARGE FIRE: Water spray, fog or regular foam. Move containers from fire area if you can do it without risk. Dike fire-control water for later disposal; do not scatter the material. Use water spray or fog; do not use straight streams.

FIRE INVOLVING TANKS OR CAR/TRAILER LOADS: Fight fire from maximum distance or use unmanned hose holders 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. For massive fire, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from area and let fire burn. (ERG, 2016)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]:

Do not touch damaged containers or spilled material unless wearing appropriate protective clothing. Stop leak if you can do it without risk. Prevent entry into waterways, sewers, basements or confined areas. Cover with plastic sheet to prevent spreading. Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. DO NOT GET WATER INSIDE CONTAINERS. (ERG, 2016)

Dust mask; goggles or face shield; protective gloves (USCG, 1999)

DuPont Tychem® Suit Fabrics

No information available.

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

SKIN: IMMEDIATELY flood affected skin with water while removing and isolating all contaminated clothing. Gently wash all affected skin areas thoroughly with soap and water. IMMEDIATELY call a hospital or poison control center even if no symptoms (such as redness or irritation) develop. IMMEDIATELY transport the victim to a hospital for treatment after washing the affected areas.

INHALATION: IMMEDIATELY leave the contaminated area; take deep breaths of fresh air. IMMEDIATELY call a physician and be prepared to transport the victim to a hospital even if no symptoms (such as wheezing, coughing, shortness of breath, or burning in the mouth, throat, or chest) develop. Provide proper respiratory protection to rescuers entering an unknown atmosphere. Whenever possible, Self-Contained Breathing Apparatus (SCBA) should be used; if not available, use a level of protection greater than or equal to that advised under Protective Clothing.

INGESTION: Some heavy metals are VERY TOXIC POISONS, especially if their salts are very soluble in water (e.g., lead, chromium, mercury, bismuth, osmium, and arsenic). IMMEDIATELY call a hospital or poison control center and locate activated charcoal, egg whites, or milk in case the medical advisor recommends administering one of them. Also locate Ipecac syrup or a glass of salt water in case the medical advisor recommends inducing vomiting. Usually, this is NOT RECOMMENDED outside of a physician's care. If advice from a physician is not readily available and the victim is conscious and not convulsing, give the victim a glass of activated charcoal slurry in water or, if this is not available, a glass of milk, or beaten egg whites and IMMEDIATELY transport victim to a hospital. If the victim is convulsing or unconscious, do not give anything by mouth, assure that the victim's airway is open and lay the victim on his/her side with the head lower than the body. DO NOT INDUCE VOMITING. IMMEDIATELY transport the victim to a hospital.

OTHER: Since this chemical is a known or suspected carcinogen you should contact a physician for advice regarding the possible long term health effects and potential recommendation for medical monitoring. Recommendations from the physician will depend upon the specific compound, its chemical, physical and toxicity properties, the exposure level, length of exposure, and the route of exposure. (NTP, 1992)

Physical Properties

Flash Point: data unavailable

Lower Explosive Limit (LEL): data unavailable

Upper Explosive Limit (UEL): data unavailable

Autoignition Temperature: data unavailable

Melting Point: data unavailable

Vapor Pressure: data unavailable

Vapor Density (Relative to Air): data unavailable

Specific Gravity: greater than 1 at 68 ° F (USCG, 1999)

Boiling Point: data unavailable

Molecular Weight: 156.08 (NTP, 1992)

Water Solubility: less than 0.1 mg/mL at 72° F (NTP, 1992)

Ionization Potential: data unavailable

IDLH: 15 mg/m3 As Cr(VI); A potential occupational carcinogen. (NIOSH, 2016)

AEGLs (Acute Exposure Guideline Levels)

No AEGL information available.

ERPGs (Emergency Response Planning Guidelines)

No ERPG information available.

PACs (Protective Action Criteria)

Regulatory Information

The Regulatory Information fields include information from the U.S. Environmental Protection Agency's Title III Consolidated List of Lists, the U.S. Department of Homeland Security's Chemical Facility Anti-Terrorism Standards, and the U.S. Occupational Safety and Health Administration's Process Safety Management of Highly Hazardous Chemicals Standard List (see more about these data sources).

EPA Consolidated List of Lists

(EPA List of Lists, 2015)

DHS Chemical Facility Anti-Terrorism Standards (CFATS)

No regulatory information available.

OSHA Process Safety Management (PSM) Standard List

No regulatory information available.

Alternate Chemical Names

This section provides a listing of alternate names for this chemical, including trade names and synonyms.

C.I. 77223

C.I. PIGMENT YELLOW 33

CALCIUM CHROMATE

CALCIUM CHROMATE (CACRO4)

CALCIUM CHROMATE (VI)

CALCIUM CHROMATE DIHYDRATE

CALCIUM CHROMATE(CACRO4)

CALCIUM CHROMATE(VI) (CACRO4)

CALCIUM CHROME YELLOW

CALCIUM CHROMIUM OXIDE (CACRO4)

CALCIUM CHROMIUM OXIDE(CACRO4)

CALCIUM MONOCHROMATE

CHROMIC ACID, CALCIUM SALT (1:1)

GELBIN

GELBIN YELLOW ULTRAMARINE

STEINBUHL YELLOW

YELLOW ULTRAMARINE

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NOAA Office of Response and Restoration, US GOV

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Chemical Identifiers | Hazards | Response Recommendations | Physical Properties | Regulatory Information | Alternate Chemical Names The Chemical Identifier fields include common identification numbers, the NFPA diamond U.S. Department of Transportation hazard labels, and a general description of the chemical. The information in CAMEO Chemicals comes from a variety of data sources.

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Hexavalent chromium is a form of the metallic element chromium. Chromium is a naturally occurring element found in rocks, animals, plants, soil, and volcanic dust and gases.

Source
Niehs.nih.gov 4/4
Very reliable source.
Very well organized.
No ads popped up.

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Chromic acid reacts with alcohols to form a chromic ester in which the alcohol oxygen atom bridges the carbon and chromium atoms.

Source
Sciencedirect.com 3/4
Very descriptive site. No ads popping up. Information very organized, super easy to find.

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Mechanism of Oxidation by Chromium(VI)

Chromic acid (H ₂CrO ₄) reacts with alcohols to form a chromic ester in which the alcohol oxygen atom bridges the carbon and chromium atoms. The ester forms by nucleophilic attack of the alcohol oxygen atom on the chromium atom. This reaction is analogous to an S N 2 reaction with a─OH group of chromic acid as the leaving group.

In the second step of the reaction, water extracts a hydrogen atom from the alcohol carbon, the electron pair in the C─H bond acts as a nucleophile, and the O─Cr bond in the chromic ester breaks to form a carbon-carbon double bond.

In an aqueous acid solution, chromic acid converts aldehydes to carboxylic acids. Before this second occurs, the aldehyde reacts with water to give a 1, 1-diol, called a gem-diol. gem-diols result from an addition reaction to the carbonyl group, a process that we will discuss in Chapter 18.

The gem-diol is an alcohol. One of its hydroxyl groups is oxidized by way of a chromic half-ester in the same manner as alcohols. The resulting compound retains the hydroxyl group of the original chromic half-ester and is a carboxylic acid.

gem-diols form in low concentration in equilibrium with the aldehyde. However, when they are converted into chromic acid half-esters and oxidized, they continue to form until the oxidation is complete. When a primary alcohol is oxidized by PCC, water is absent. So, a gem-diol cannot form, and the aldehyde is not further oxidized.

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URL: https://www.sciencedirect.com/science/article/pii/B9780128007808000152

Mechanism of Oxidation by Chromium(VI)

Chromic acid (H ₂CrO ₄) oxidizes alcohols in aqueous solutions of sodium dichromate. It reacts with alcohols to form a chromic ester in which the alcohol oxygen atom bridges the carbon and chromium atoms. Thus, the ester forms by nucleophilic attack of the alcohol's oxygen atom on the chromium atom.

In the second step, the chromic ester undergoes an α-elimination reaction. Most of the elimination processes discussed in prior chapters have been β-elimination reactions, which form a carbon-carbon double bond. In this oxidation step, a carbon-oxygen double bond forms.

In an aqueous acid solution, chromic acid converts aldehydes to carboxylic acids. Before this second reaction occurs, the aldehyde reacts with water to give a 1,1-diol, called a gem-diol. gem-Diols result from an addition reaction to the carbonyl group, a process that we will discuss in Chapter 20.

The gem-diol is an alcohol. One of its hydroxyl groups is oxidized by way of a chromic half-ester in the same manner as alcohols. The resulting compound retains the hydroxyl group of the original chromic half-ester and is a carboxylic acid.

gem-diols form in low concentration in equilibrium with the aldehyde. However, when they are converted into chromic acid half-esters and oxidized, they continue to form until the oxidation is complete. When a primary alcohol is oxidized by PCC, water is absent. So, a gem-diol cannot form, and the aldehyde is not further oxidized.

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URL: https://www.sciencedirect.com/science/article/pii/B9780128128381500165

2.7.5.2 On Resins/Polymers

Gelbard et al. have prepared a number of neutral and acidic supported ammonium chromates. Neutral resins were found to be generally more effective than acidic resins. The large differences in reactivity between different unbound, soluble alkylammonium chromates (Section 2.7.6.1) are not so pronounced with the polymer-supported oxidants. Some comments about the reactivity of these supported oxidants were made: (i) quaternary ammonium salts are more reactive than the tertiary pyridinium chromates; (ii) the reactivity of a complex chromate XCrO ₃− was found to increase as the basicity of X − decreases. Best results were obtained with trifluoroacetatochromates; and (iii) nonpolar solvents, such as cyclohexane, enhance reactivity by promoting the diffusion of substrates into the resin. For similar reasons, macroporous resins are preferred to gel types, even when well swollen.

The reagents prepared by Gelbard et al. were found to be selective for saturated alcohols, since the oxidation of allylic or benzylic alcohols requires either a vast excess of oxidant or prolonged reaction times.

To overcome the problems of toxicity and work-up associated with many inorganic oxidants, it would be advantageous to develop a catalytic supported oxidant. Towards this aim, chromium(III)-impregnated Nafion 511 (NAFK) has been used as a catalytic oxidant in the presence of t-butyl hydroperoxide. This reagent gives good yields of ketones (80-100%), but unfortunately oxidation of primary alcohols leads to the formation of complex mixtures.

Poly(vinylpyridinium chlorochromate) (PVPCC) is a mild oxidant for primary, secondary, allylic and benzylic alcohols. Unfortunately, optimum conditions require the use of very nonpolar solvents (best is cyclohexane) at 80 °C. More polar solvents (that would be more generally useful in synthesis) severely retard the rate of oxidation, thus necessitating an increase in the amount of oxidant used. Oxidations were found to have high inital rates, but were very slow to go to completion due to the inaccessibility of the chromium. This can be overcome by using a lower loading of oxidant or by an alternative preparation of the polymer, where the addition of 1-5% divinylbenzene gives a much more porous resin.

Poly(vinylpyridinium dichromate) can be prepared in a similar way to PVPCC. To be effective it must be used in the presence of water and in the most nonpolar solvent possible. It gives moderate to good yields, but long reaction times may be required for the reaction to proceed to completion. Even with the long reaction times, very little overoxidation is observed. Up to five oxidation-regeneration cycles may be completed without significant loss of activity.

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URL: https://www.sciencedirect.com/science/article/pii/B9780080523491001906

7.09.2 Oxidation Using Metal-Based Oxidants

7.09.2.1 Chromium(VI) in Sulfuric Acid in Water (Jones Reagent)

Chromic acid combined with sulfuric acid in water, which is referred to as the Jones reagent, has been widely used as a convenient oxidizing reagent of ethers. Oxidation of 6-hydroxy-2-(4-methoxyphenyl)-2-methyl-2 H-pyran-3(6 H)-ones with the Jones reagent affords diones (equation 1), which are intermediates in the synthesis of substituted pyrrolidinones and oxaspiro derivatives.

7.09.2.2 PCC

PCC is a good oxidant in allylic oxidation of activated methylene compounds. For example, 3,6-dihydro-4-methyl-2 H-pyran is oxidized by PCC to the corresponding lactones in good yield (equation 2).

Phenyloxiranes are cleaved by the reaction with PCC in the presence of 4 Å molecular sieves to lead to carbonyl compounds (75%) (equation 3). Under similar reaction conditions, alkyl-substituted oxiranes are converted into α-hydroxy ketones as a major product (equation 4).

PCC can behave as a good oxidizing agent for oxidation of CåC double bond activated by oxygen atom. Thus, PCC oxidizes dihydrofuran to the corresponding lactone in 85% yield (equation 5). The oxidation reaction involves a 1,2-hydride shift from the α-carbon to the β-carbon of the ether.

Alternatively, in the case of α,α′-disubstituted enol ethers having no hydrogens such as 3,4,5,6,7,8-hexahydro-2 H-1-benzopyran, oxidative cleavage of the CåC double bond takes place, giving keto lactones in good yield (equation 6).

Selective oxidation of 1,4-dioxene derivatives can be achieved by PCC. Thus, the reaction of 2-alkynoyl-1,4-cyclodioxene with PCC followed by treatment with NaOH provides an α-keto acid (54%) (equation 7).

PCC has been employed toward the oxidation of furan derivatives. Thus, 5-methyl-2-furylcarbinol undergoes oxidative ring enlargement to form hexenulose (equation 8).

By the use of PCC, 2,5-dialkylfurans are easily oxidized to trans-α,β-unsaturated 1,4-dicarbonyl compounds through oxidative ring fission. The reaction is accompanied by isomerisation of the double bond to form the trans-product exclusively (equation 9).

PCC shows high reactivity toward nucleophilic furans such as 2-alkylthiofurans, which are rapidly converted into methyl ( Z)-4-oxo-2-pentenoate by the action of the reagent in dichloromethane. Here, rapid cis/ trans isomerization is based on the acidic character of PCC, and the cis-isomer is obtained exclusively (equation 10).

Both cyclic and linear silyl enol ethers can be easily converted into α-iodocarbonyl compounds by using PCC in the presence of iodine in dichloromethane (equation 11). The reaction of dihydropyran is reported to form the α-iodolactone in 52% yield (equation 12).

7.09.2.3 Pyridinium Dichromate

Pyridinium dichromate (PDC) combined with chlorotrimethylsilane (TMSCl) serves as a selective deprotection-oxidation reagent of silyl ethers and silyl enol ethers. For example, tert-butyldimethylsilyl ethers are subject to the deprotection-oxidation reaction, affording the corresponding ketones in high yields (equation 13). The combination of PDC and TMSCl is employed as an effective oxidant for the preparation of quinines from hydroquinone silyl ethers (equation 14).

The PDC/ t-BuOOH system is used for the conversion of dihydropyran into 5,6-dihydro-2 H-pyran-2-ones together with the formation of a small amount of tert-butylperoxy derivative as a byproduct (equation 15).

7.09.2.4 Ruthenium-Based Oxidants

RuO ₄ acts as an effective simultaneous oxidant of both the C-H bond of an ether moiety to generate a lactone and the CåC bond to create an epoxide. Thus, the oxidation of a pregnenolone derivative involving both a cyclic ether and a CåC double bond affords an epoxy lactone as a major product (equation 16).

The oxidation of 2,5-dimethylfuran with RuO ₂ and NaIO ₄ leads to a carbon-oxygen bond cleaved product, 2,5-hexanedione (equation 17).

In general, carbonyl groups are inert under the oxidation conditions created by Ru (equation 18), but a Baeyer-Villiger reaction can be induced in preference to an oxidation of the ether moiety when sodium hypochlorite is employed as a cooxidant (equations 18 and 19).

The oxidation using RuCl ₃-NaIO ₄ system is successfully extended to the lactonization of a bicyclic ether/lactone to a bicyclic lactone which is an intermediate for the synthesis of drugs displaying antibacterial activity (equation 20).

7.09.2.5 CAN

CAN has been used for the oxidation of ethers. Thus, catechol methyl ethers are readily oxidized to quinines by CAN. Partial demethylation is induced to convert these materials into intramolecular quinhydrones (equation 21), which are intermediates of daunomycinones.

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URL: https://www.sciencedirect.com/science/article/pii/B9780080977423007102

A OXIDATION OF A COMMERCIAL MIXTURE OF cis- AND trans-4-t-BUTYLCYCLOHEXANOL

The chromic acid oxidizing reagent is prepared by dissolving 13.4 g of chromium trioxide in 25 ml of water. To this solution is added 12 ml of concentrated sulfuric acid. An additional minimum quantity of water is added if necessary to dissolve any precipitated salts.

A solution of 15.6 g (0.1 mole) of 4- t-butylcyclohexanol in 250 ml of acetone is placed in a 500-ml three-necked flask fitted with a dropping funnel, a thermometer, and a mechanical stirrer. The stirred solution is cooled in a water bath to 20°, and the chromic acid oxidizing solution is added from the dropping funnel slowly, so that the temperature of the reaction mixture does not exceed 35°. The addition is continued until the orange color of the reagent persists for about 20 minutes. The excess oxidizing agent is destroyed by the addition of a small quantity of isopropyl alcohol (1 ml is usually sufficient).

The mixture is decanted into an Erlenmeyer flask, the residual green salts are washed with two 15-ml portions of acetone, and the washings are added to the main acetone solution. Cautiously, sodium bicarbonate (approx. 13 g) is added to the solution with swirling until the pH of the reaction mixture is neutral. The suspension is filtered, and the residue is washed with 10-15 ml of acetone. The filtrate is transferred to a round-bottom flask and concentrated on a rotary evaporator under an aspirator while the flask temperature is maintained at about 50°. The flask is cooled and the residue transferred to a separatory funnel. (If solidification occurs, the residue may be dissolved in ether to effect the transfer.) To the funnel is added 100 ml of saturated sodium chloride solution, and the mixture is extracted with two 50-ml portions of ether. The ether extracts are combined, washed with several 5-ml portions of water, dried over anhydrous magnesium sulfate, and filtered into a round-bottom flask. The ether may be distilled away at atmospheric pressure (steam bath) or evaporated on a rotary evaporator. On cooling, the residue should crystallize. If it does not, it may be treated with 5 ml of 30-60° petroleum ether, and crystallization may be induced by cooling and scratching. The crystalline product is collected by filtration and recrystallized from aqueous methanol. 4- t-Butylcyclohexanone has mp 48-49° (yield 60-90%).

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URL: https://www.sciencedirect.com/science/article/pii/B9780125049504500046

3.3.5 Other inorganic acids

Zirconium resists chromic acid up to 30% at temperatures to 100 °C but it is not suitable for handling certain chrome-plating solutions that contain fluoride catalysts. Zirconium is also resistant to certain mixed acids that include sulfuric-nitric, sulfuric-hydrochloric, and phosphoric-nitric mixtures. The sulfuric acid concentration must be below 70%. Zirconium is aggressively attacked in 1:3 volume mixtures of nitric and hydrochloric acids (aqua regia). In the volume mixture, zirconium is attacked more slowly than in the aqua regia. In mixtures greater than the 3:1 ratio, zirconium becomes resistant. Data for some mixed acid systems are given in Table 10.

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5.1.8 Chromic Acid Regeneration

In many industrial processes using chromic acid, a spent acid stream containing trivalent chromium and/or cationic contaminants is obtained. Disposal of this stream would require chemical reduction of any remaining hexavalent chromium followed by precipitation of chromium hydroxide and filtration. Electrochemical regeneration is an attractive alternative. It is used on spent acid streams generated in three applications:

(1)

Chromic acid used in the oxidation of some organic compounds.

(2)

Chromic acid used in surface etching of plastic parts prior to metallizing.

(3)

Chromic acid plating solutions.

In all these cases, anodic oxidation of trivalent to hexavalent chromium is the main desired reaction. To achieve high anodic CE, selection of the anode material is most important. Lead dioxide is the material of choice. Low anodic CD and high anolyte turbulence also contribute to high CE, even as the concentration of trivalent chromium is reduced to low levels. At the membrane, removal of cationic contaminants is desired; however, because their concentration is typically low, poor membrane CE is to be expected with most of the current carried by hydrogen ions. If these cationic contaminants have sufficiently noble characteristics, such as copper, they may plate out on the cathode, but again at poor CE. Contact of the membrane with the cathode should, therefore, be avoided. The main cathodic reaction is the evolution of hydrogen.

The catholyte for the first two cases is dilute sulfuric acid. In the last case, the choice of catholyte is more limited, because in chrome plating, the content of sulfate ions in the plating bath must be controlled within narrow limits. Because the anion rejection of the membrane is not absolute, sulfuric acid of the typical concentration range 10-20% may result in excessive sulfate contamination of the plating bath. To avoid this problem, anions such as carbonate, formate, or citrate have been used in the catholyte.

For this application, a cylindrical cell design offers several advantages:

(1)

The cell is installed in a corrosion-proof container without any external gaskets; the possibility of a chromic acid spill is, therefore, greatly reduced.

(2)

The external anode has more area than the membrane and the cathode. This results in low anodic CD, which promotes high anode efficiency.

(3)

The centrally located cathode can be pulled easily for cleaning.

(A diagram of such a cylindrical cell is shown in Fig. 5.46.)

The components of the cathode compartment are shown in Fig. 5.45. On the left of is the entire cathode compartment consisting of an outer titanium cage supporting the conical bottom closure made of Teflon. The three components of the top closure, designed very similarly to the bottom closure, are shown in the center of the bottom of the picture. An outer sleeve made of Teflon has a conical inner opening. The conical Teflon plug, with its three VITON O-rings, has a diameter and taper that matches the conical opening of the outer sleeve. For assembly, the top of the cylindrical membrane is inserted from the bottom into the opening of the outer sleeve. The plug is then inserted into the inside of the tubular membrane and forced into the taper of the outer sleeve by bolting the titanium ring to the top of the sleeve. The dimensions of the tubular membrane are 7.6 cm diameter × 1.2 m length. Two examples of an inner support to prevent membrane-cathode contact are shown on the right of the picture. A schematic and a picture showing an installation of three of these cells in connection with a shared catholyte tank is shown in Appendix A.

Ahmed has developed a mathematical model to estimate contaminant fluxes due to migration, diffusion, and convection in the electrolytic regeneration of contaminated hard chrome plating baths using Nafion 117 as the separator.

The ionic mobilities of Cu, Fe, and Ni through Nafion 117 were found to be 5.4 × 10 ⁻¹⁰, 1.7 × 10 ⁻¹⁰, and 5.2 × 10 ⁻¹⁰ cm ²/Vs, respectively [12].

Trace contaminants, such as copper, may plate out on the cathode. If the membrane touches the cathode under these circumstances, dendrites growing on the cathode may grow through the membrane. If the tip of a dendrite comes close to the anolyte, rapid plating of chromium metal may occur. It appears that the chromium plates out in nodules on the anolyte surface of the membrane. As in many other electrolytic applications, contact of the membrane with the cathode should be avoided.

Hexavalent chrome plating will not resume after a short (<1 second) interruption of current. If the current is interrupted once per hour, small dentrites which have perforated the membrane will be prevented from causing major membrane destruction. The tip of the dentrite will reduce chromic acid to Cr+++ instead, but that will be reoxidized at the anode.

A chromic acid regeneration system incorporating three of these cells is shown in Appendix A.

A laboratory scale cell for chromic acid regeneration is shown in Fig. 9.11.

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Chromic acid (H 2CrO 4) reacts with alcohols to form a chromic ester in which the alcohol oxygen atom bridges the carbon and chromium atoms. The ester forms by nucleophilic attack of the alcohol oxygen atom on the chromium atom. This reaction is analogous to an S N 2 reaction with a─OH group of chromic acid as the leaving group.

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Chromium(|||) Oxide is a Chromium source suitable for glass, optic and ceramic applications.

Source
Americanelements.com 2/4
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SECTION 1. IDENTIFICATION

Product Name: Chromium(III) Oxide

Product Number: All applicable American Elements product codes, e.g. CR3-OX-02 , CR3-OX-03 , CR3-OX-04 , CR3-OX-05

CAS #: 1308-38-9

Relevant identified uses of the substance: Scientific research and development

Supplier details:
American Elements
10884 Weyburn Ave.
Los Angeles, CA 90024
Tel: +1 310-208-0551
Fax: +1 310-208-0351

Emergency telephone number:
Domestic, North America: +1 800-424-9300
International: +1 703-527-3887

SECTION 2. HAZARDS IDENTIFICATION

SECTION 3. COMPOSITION/INFORMATION ON INGREDIENTS

Substances
CAS No. / Substance Name:
1308-38-9 Chromium(III) oxide
Identification number(s):
EC number: 215-160-9

SECTION 4. FIRST AID MEASURES

SECTION 5. FIREFIGHTING MEASURES

Extinguishing media
Suitable extinguishing agents
Product is not flammable. Use fire-fighting measures that suit the surrounding fire.
Special hazards arising from the substance or mixture
If this product is involved in a fire, the following can be released:
Metal oxide fume
Advice for firefighters
Protective equipment:
Wear self-contained respirator.
Wear fully protective impervious suit.

SECTION 6. ACCIDENTAL RELEASE MEASURES

SECTION 7. HANDLING AND STORAGE

SECTION 8. EXPOSURE CONTROLS/PERSONAL PROTECTION

Additional information about design of technical systems:
Properly operating chemical fume hood designed for hazardous chemicals and having an average face velocity of at least 100 feet per minute.
Control parameters
Components with limit values that require monitoring at the workplace:
1308-38-9 Chromium(III) oxide (100.0%)
PEL (USA) Long-term value: 0.5 mg/m ³ as Cr
REL (USA) Long-term value: 0.5 mg/m ³ as Cr; See Pocket Guide App. C
TLV (USA) Long-term value: 0.5 mg/m ³ as Cr
EL (Canada) Long-term value: 0.5 mg/m ³ as Cr
Additional information: No data
Exposure controls
Personal protective equipment
Follow typical protective and hygienic practices for handling chemicals.
Keep away from foodstuffs, beverages and feed.
Remove all soiled and contaminated clothing immediately.
Wash hands before breaks and at the end of work.
Maintain an ergonomically appropriate working environment.
Breathing equipment:
Use suitable respirator when high concentrations are present.
Recommended filter device for short term use:
Use a respirator with type P100 (USA) or P3 (EN 143) cartridges as a backup to engineering controls. Risk assessment should be performed to determine if air-purifying respirators are appropriate. Only use equipment tested and approved under appropriate government standards.
Protection of hands:
Impervious gloves
Inspect gloves prior to use.
Suitability of gloves should be determined both by material and quality, the latter of which may vary by manufacturer.
Penetration time of glove material (in minutes): No data available
Eye protection: Safety glasses
Body protection: Protective work clothing.

SECTION 9. PHYSICAL AND CHEMICAL PROPERTIES

SECTION 10. STABILITY AND REACTIVITY

Reactivity
No data available
Chemical stability
Stable under recommended storage conditions.
Thermal decomposition / conditions to be avoided:
Decomposition will not occur if used and stored according to specifications.
Possibility of hazardous reactions
Reacts with strong oxidizing agents
Conditions to avoid
No data available
Incompatible materials:
Oxidizing agents
Hazardous decomposition products:
Metal oxide fume

SECTION 11. TOXICOLOGICAL INFORMATION

SECTION 12. ECOLOGICAL INFORMATION

SECTION 13. DISPOSAL CONSIDERATIONS

Waste treatment methods
Recommendation
Consult official regulations to ensure proper disposal.
Uncleaned packagings:
Recommendation:
Disposal must be made according to official regulations.

SECTION 14. TRANSPORT INFORMATION

SECTION 15. REGULATORY INFORMATION

SECTION 16. OTHER INFORMATION

Safety Data Sheet according to Regulation (EC) No. 1907/2006 (REACH). The above information is believed to be correct but does not purport to be all inclusive and shall be used only as a guide. The information in this document is based on the present state of our knowledge and is applicable to the product with regard to appropriate safety precautions. It does not represent any guarantee of the properties of the product. American Elements shall not be held liable for any damage resulting from handling or from contact with the above product. See reverse side of invoice or packing slip for additional terms and conditions of sale. COPYRIGHT 1997-2018 AMERICAN ELEMENTS. LICENSED GRANTED TO MAKE UNLIMITED PAPER COPIES FOR INTERNAL USE ONLY.

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product: chromium(iii) oxide 1308-38-9 cr2o3

# data[].attributes.attachment_link.description
Product Name: Chromium(III) Oxide Product Number: All applicable American Elements product codes, e.g. CR3-OX-02 , CR3-OX-03 , CR3-OX-04 , CR3-OX-05 CAS #: 1308-38-9 Relevant identified uses of the substance: Scientific research and development Supplier details: American Elements10884 Weyburn Ave.Los Angeles, CA 90024Tel: +1 310-208-0551Fax: +1 310-208-0351 Emergency telephone number: Domestic, North America: +1 800-424-9300International: +1 703-527-3887 SubstancesCAS No.

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-Chromium was discovered in 1797.
-Chromium was commonly used in aluminum.
-Chromium was known as Siberian red lead.
-Louis Nicolas Vauquelin discovered Chromium.

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Livescience.com 3/4
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Known for its silver, shiny appearance, chromium is used to coat cars, stoves and other appliances to protect them from corrosion and to improve their looks. Chromium's high melting point and stable structure also make it useful in the textile and refractory industries. When combined with other elements, chromium makes vibrant colors and is used as a dye, which is what originally earned it its name from the Greek word chroma for "color."

It is naturally found in compounds in the earth's crust. However, consuming high levels of chromium in polluted drinking water or inhaling fumes of the heated element can cause ulcers, cancer and other health problems.

Just the facts

Atomic number (number of protons in the nucleus): 24

Atomic symbol (on the periodic table of elements): Cr

Atomic weight (average mass of the atom): 51.9961

Density: 4.13 ounces per cubic inch (7.15 grams per cubic cm)

Phase at room temperature: solid

Melting point: 3,465 degrees Fahrenheit (1,907 degrees Celsius)

Boiling point: 4,840 F (2,671 C)

Number of natural isotopes (atoms of the same element with a different number of neutrons): 4

Most common isotope: Cr-52

(Image credit: Greg Robson/Creative Commons, Andrei Marincas Shutterstock)

Discovery of chromium

French chemist Louis Nicolas Vauquelin first isolated chromium from a bright red mineral called Siberian red lead, now known as lead chromate (PbCrO ₄) in 1797. According to John Emsley in his book, " Nature's Building Blocks: An A-Z Guide to the Elements" (Oxford University Press, 1999), it took Vauquelin a year before he was able to precipitate out the lead and obtain pure chromium. He mixed the chromium in a variety of solutions and was intrigued by the many colors it produced, thereby naming the element after the Greek word chroma meaning "color."

Sources of chromium

Chromium is the 21st most common element found in the Earth's crust, but it is not found in its free metal form. Instead, it is principally found in chromite ore, according to Robert E. Krebs in his book, " The History and Use of Our Earth's Chemical Elements: A Reference Guide" (Greenwood Publishing Group, 2006). Chromite is mined in Zimbabwe, Russia, New Zealand, Turkey, Iran, Albania, Finland, the Philippines and Madagascar. About 20,000 tons of chromium metal are produced each year, and there are still about a billion tons of unexploited deposits in Greenland, Canada, and the United States, according to Emsley. Chromium metal is then obtained by heating the chromite ore in the presence of aluminum or silicon, according to the Jefferson Lab.

Properties of chromium

Chromium is a transition metal in Group 6 on the Periodic Table of Elements. In its pure form, chromium is a silvery, lustrous, hard metal that has a high polish, ideal for electroplating.

The most important chromium compounds are the chromates of sodium and potassium, the dichromates, and potassium and ammonium chrome alums, according to the Los Alamos National Laboratory. Chromium compounds are toxic and should be handled with care.

Chromium compounds are all vividly colored and are used as pigments - bright green, yellow, red and orange. Rubies are red because of chromium, and glass treated with chromium has an emerald green color, according to the Royal Society of Chemistry (RSC).

Used for protection and beauty

Using a technique called electroplating, a thin layer of chromium can coat metal and plastic objects, including car parts and household appliances, to give a shiny, attractive finish. For example, automotive designers use chrome rims and wheels to spruce up their cars. Chrome plating is not only used for looks; because the chromium forms a protective oxide layer on the surface, chrome-plated objects resist corrosion, according to Krebs.

Stainless steel is an alloy of iron and at least 10.5 percent chromium. It is highly resistant to corrosion. It is used in kitchen cutlery, appliances and cookware such as stainless steel pans and skillets.

About 90 percent of leather is chrome tanned, according to Emsley. During this process, chromium sulfate is used to treat animal skin and turn it into leather that is resistant to hot water that can cause degradation.

Kilns and furnaces use bricks made of chromite ore, which retains strength at high temperatures. The textile industry uses chromium ions to help adhere dyes to fabric. Chromium's high melting point, moderate thermal expansion and crystalline structure stability make it suitable for these purposes.

Dangerous in excess

Though its specific role in humans is unclear, studies have shown that chromium is an essential trace element that is found in RNA and helps the body to use glucose. Chromium is most concentrated in the placenta, and its presence in the body decreases with age.

A safe amount is about 1 milligram per day, according to the RSC. Foods such as brewer's yeast, wheat germ and kidney are rich in chromium. However, it is poisonous in excess.

In the 2000 film "Erin Brockovich," Julia Roberts portrays an environmental activist and legal clerk who leads a case against a gas and electric company for contaminating drinking water with chromium(VI), a toxic compound known to cause cancer, according to the U.S. Occupational Safety and Health Administration (OSHA). Though Brockovich won the case in real life and in the movie, scientists have criticized her lack of evidence showing that chromium(VI), and not other factors, was the cause of the numerous health issues including cancer in the community of Hinkley, Calif. However, several studies in the past few years have linked chromium(VI) in tap water to cancer and the EPA has set a drinking water concentration limit for the element to protect public health.
Additional resources
Excessive exposure to chromium can also cause chrome ulcers, particularly when working with it for months while chrome-plating or leather tanning, according to Emsley. Chrome ulcers are itchy and raw holes in the skin or the stomach. If dust containing chromium is inhaled, industrial workers are more prone to ulcers in the nasal cavity and lung cancer. Additionally, a 2017 study published in European Journal of Clinical Nutrition linked high levels of urinary chromium to cardiovascular disease and diabetes.

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Known for its silver, shiny appearance, chromium is used to coat cars, stoves and other appliances to protect them from corrosion and to improve their looks. Chromium's high melting point and stable structure also make it useful in the textile and refractory industries.

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Chromium trioxide is a strong oxidizing agent that is not soluble in most organic solvents and tends to explode in the presence of organic compounds and solvents.

Source
Organic-chemistry.org 1/4
Not very well organized information. No ads. Color coordinated information.

# data[].attributes.attachment_link.readable_text
Chromium trioxide is a strong oxidizing agent that is not soluble in most organic solvents and tends to explode in the presence of organic compounds and solvents. In water, it forms chromic acid and anhydrides, from which salts such as sodium dichromate (Na ₂Cr ₂O ₇) and pyridinium dichromate are commercially available.

Chromium trioxide is soluble in tert-butyl alcohol, pyridine (see Sarett Reagent, Collins Reagent) and acetic anhydride, although care must be taken to follow the given procedures, because these solutions tend to explode. A solution of chromium trioxide in aqueous sulfuric acid can be safely mixed with acetone ( Jones Reagent). If this mixture is slowly added to an alcohol in acetone, oxidation products such as carbonyl compounds and carboxylic acids can be isolated in good yields ( Jones Oxidation).

A full review of chromium-based reagents can be found in the book written by Tojo and Fernández ( Oxidation of Alcohols to Aldehydes and Ketones, Springer Berlin, 2006, 1-97.).

Attention: Chromium (VI) compounds are toxic and must be handled with care.
Recent Literature

Benzyl alcohols and benzyl TBDMS ethers were efficiently oxidized to the corresponding carbonyl compounds in high yield with periodic acid catalyzed by CrO ₃ at low temperature (-78 °C). The oxidation procedure was highly functional group tolerant and very selective for the TBDMS group over the TBDPS group.
S. Zhang, L. Xu, M. L. Trudell, Synthesis, 2005, 1757-1760.

Benzyl alcohols and benzyl TBDMS ethers were efficiently oxidized to the corresponding carbonyl compounds in high yield with periodic acid catalyzed by CrO ₃ at low temperature (-78 °C). The oxidation procedure was highly functional group tolerant and very selective for the TBDMS group over the TBDPS group.
S. Zhang, L. Xu, M. L. Trudell, Synthesis, 2005, 1757-1760.

CrO ₃ is an efficient catalyst for benzylic oxidation with periodic acid as the terminal oxidant in acetonitrile. Substituted electron-poor toluenes and diarylmethanes were oxidized to the corresponding substituted benzoic acids and ketones in excellent yields. Benzyl ethers such as isochroman and phthalan were converted to 3,4-dihydroisocoumarin and phthalide in quantitative yields.
S. Yamazaki, Org. Lett., 1999, 1, 2129-2132.

A sequential PdCl ₂/CrO ₃-promoted Wacker process followed by an acid-mediated dehydration enables the synthesis of β-substituted and β,β-disubstituted α,β-unsaturated methyl ketones from homoallyl alcohols with a terminal double bond, whereas internal homoallyl alcohols delivered regioselectively nonconjugated unsaturated carbonyl compounds under the same protocol.
V. Bethi, R. A. Fernandes, J. Org. Chem., 2016, 81, 8577-8584.

A CrO ₃-catalyzed oxidation of primary alcohols to carboxylic acids proceeds smoothly with only 1-2 mol % of CrO ₃ and 2.5 equivalents of H ₅IO ₆ in wet MeCN to give the carboxylic acids in excellent yield. No significant racemization is observed for alcohols with adjacent chiral centers. Secondary alcohols are cleanly oxidized to ketones.
M. Zhao, J. Li, Z. Song, R. Desmond, D. M. Tschaen, E. J. J. Grabowski, P. J. Reider, Tetrahedron Lett., 1998, 39, 5323-5326.

Trihaloacetic acids can been converted to trichloromethyl and tribromomethyl ketones in good yield by a catalyzed reaction with aldehydes followed by oxidation. A coupling of organozinc intermediates with trichloroacetyl chloride gives trichloromethyl ketones.
E. J. Corey, J. O. Link, Y. Shao, Tetrahedron Lett., 1992, 33, 3435-3438.

CrO ₃ is an efficient catalyst for benzylic oxidation with periodic acid as the terminal oxidant in acetonitrile. Substituted electron-poor toluenes and diarylmethanes were oxidized to the corresponding substituted benzoic acids and ketones in excellent yields. Benzyl ethers such as isochroman and phthalan were converted to 3,4-dihydroisocoumarin and phthalide in quantitative yields.
S. Yamazaki, Org. Lett., 1999, 1, 2129-2132.

A reaction between dialkyl acetylenedicarboxylates and β-aminoketones promoted by triphenylphosphine allows an efficient one-pot synthesis of polysubstituted 2,5-dihydropyrrole derivatives. The prepared 2,5-dihydropyrroles can be easily oxidized to the corresponding pyrrole derivatives with chromium trioxide.
M. Anary-Abbasinejad, E. Poorhassan, A. Hassanabadi, Synlett, 2009, 1929-1932.

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Chromium trioxide is a strong oxidizing agent that is not soluble in most organic solvents and tends to explode in the presence of organic compounds and solvents. In water, it forms chromic acid and anhydrides, from which salts such as sodium dichromate (Na 2Cr 2O 7) and pyridinium dichromate are commercially available.

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Source
Periodictable.com 3/4
This source intends to infor the reader about science. No ads on the site. They base their studies on other scientific articles. Offers a lot of useful information.

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Complete and detailed technical data about the element Chromium in the Periodic Table.

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# of protons: 24
# of neutrons: 28
# of electrons

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Atomic symbol: Cr
Atomic number: 24