Is aqua regia flammable?

This blog post will answer the question, “Is aqua regia flammable” and cover topics like the flammability of aqua regia, and frequently asked questions related to the topic.

Is aqua regia flammable?

No, aqua regia is not flammable. Although it is not combustible, concentrating the combination may produce a powerful oxidant, which can induce ignition when combined with reducing agents or combustibles. Can produce dangerous hydrogen gas when reacting with metals.

Precautions

Before you begin, do the following preparations:

  • Read the manufacturer’s Safety Data Sheet for further information about the chemical.
  • Make sure you have a documented experimental protocol including safety details.
  • In the EHS Lab Emergency Response, be conversant with standard University emergency protocols.
  • Locate the closest eyewash and shower and double-check that they are operational.
  • Locate and confirm the availability of relevant Aqua Regia spill cleaning products.
  • Complete all work in a secondary vessel that is free of organic debris and clean.
  • Caution: Do not add organic material to the Aqua Regia Liquid as they may react aggressively. Any chemical with a C-H bond, such as acetone, ethanol, photoresist, or detergents, falls under this category. Organics, even at tiny levels, may render the Aqua Regia liquid unstable.
  • Always add nitric acid to hydrochloric acid while making Aqua Regia, never the other way around.
  • Aqua regia should not be kept on the shelf. Aqua Regia soon loses its potency owing to the oxidation of its reactive components, in addition to its toxic byproducts and reactions. For each usage, create a new solution.

During the workday:

  • Avoid inhalation: Use a certified chemical fume mask or another suitable ventilated enclosure for all activities. All Aqua Regia handling must be done in a fume hood with glassware.
  • Never take an Aqua Regia container out of the fume hood. Maintain a low sash as much as possible. Never elevate it higher than the recommended level (18 inches).
  • If you’re going to leave anything to soak overnight, make sure the fume hood sash is closed and the container is properly labeled. “Aqua Regia: Extremely Corrosive,” for example.
  • Avoid contact at all costs: Wear the proper PPE, which includes:
  • Lab coat and closed-toed shoes are required.
  • Protective eyewear
  • Use the Harvard EHS Glove Selection Guide to assist you to choose chemically rubber gloves that are rated for use with the precise concentrations of Nitric Acid and Hydrochloric Acid you’ll be working with. Not all gloves are designed to work with both types of materials. You must choose the right glove for the concentrations you’ll be working with. Please contact your Lab Safety Advisor for assistance in selecting a glove.
  • In addition to working in a fume hood, use acid-resistant gloves with prolonged cuffs, an acid-resistant apron, and a face shield when handling large volumes (>500mL) or when splashing is more probable.
  • After removing gloves, wash your hands completely.
  • Use Aqua Regia-compatible products and containers and be aware of any possible incompatibilities.
  • Always use glass containers (ideally Pyrex). Aqua Regia is a high-energy, possibly explosive solution. It is also quite likely to get very hot, perhaps exceeding 100°C. Use caution while handling.
  • Aqua Regia will corrode most metals and melt certain plastics.
  • Never use Aqua Regia in a closed container since the evolved gases may produce a pressure build-up and probable overpressurization. Before transferring the aqua regia to a container with a vented cover, let it cool fully.

After you’ve finished your work:

  • Follow Harvard University’s Hazardous Waste Procedures for disposing of Aqua Regia waste:
  • Corrosive/Toxic Hazardous Waste Classification
  • Use a vented cap on a glass bottle. If a vented cap isn’t available, loosely screw on a conventional top — a firmly screwed-on lid might cause pressure to build up within the bottle.
  • Make sure the trash container you’re using is clean, dry, and free of leftover solvents or chemicals.
  • Other organic materials may be found in it. In the garbage bottle, Aqua Regia should be the only waste ingredient.
  • Aqua Regia is a powerful oxidizer that will react with organic compounds.
  • Before leaving the lab, wash your hands.

Procedures in Case of an Emergency caused by Aqua Regia

In the case of skin contact, skin burns may occur. For at least 10 min, flush the body with sufficient quantities of water. Seek medical assistance.

Eye contact: Aqua Regia is caustic and unpleasant to the eyes if it comes into contact with them. Immediately flush infected eye(s) with copious amounts of water for at least 15 min. Seek medical help as soon as possible.

Inhalation: The respiratory tract may be irritated. Conscious persons should be moved to a place with clean, fresh air. If you have respiratory discomfort, cough, or chest tightness, see a doctor. The onset of signs may be delayed.

Handling of Aqua Regia

  • Always use glass containers (ideally Pyrex). Some polymers can melt, and most metals will corrode if exposed to aqua regia.
  • Aqua regia solutions should never be stored. Only mix what you’ll need, then discard after each usage.
  • In a hood with the curtain between you and the solution, mix the solution. Wear chemical splash glasses, a face shield, a lab coat, and gloves that are adequate for the job.
  • Always add the nitric acid to the HCL gently while making the aqua regia solution.
  • Toxic fumes are released when metals are dissolved in aqua regia; always deal with aqua regia in a fume hood.
  • Aqua regia solution is a high-energy, possibly explosive substance. It will most likely reach temperatures of around 100°C. Use caution while handling.
  • The exothermic process will be accelerated by adding acids or bases to aqua regia or by sprinkling it with water.
  • Allow the heated aqua regia solution to cool in an open container.
  • Aqua regia should never be kept in a closed vessel. Over time, it will oxidize into hazardous nitrosyl chloride, NO2, and chlorine fumes. This will pressurize the container, which will most likely result in an explosion.
  • It’s possible that mixing aqua regia with organic substances may result in an explosion.

Storage of Aqua Regia

Aqua regia should not be stored. Due to the oxidation of its reactive elements, aqua regia soon loses its efficacy. For each usage, create a new solution. Excessive solutions must be neutralized with sodium bicarbonate and flushed with large quantities of water before being disposed of down the drain.

Disposal of Aqua Regia

After the material has cooled, neutralize the wasted solution with sodium bicarbonate and dispose of it down the drain, followed by a thorough cleaning with plenty of water. The neutralized solution must be collected as toxic waste if the solution contains heavy metals (such as silver or chromium).

Safe Handling and Preparation of Aqua Regia

  • When handling aqua regia, proper PPE (lab coat, safety eyeglasses with side shields or splash goggles, and gloves compatible with nitric acid and HCL) should always be used.
  • Wear acid-resistant gloves with longer cuffs when handling big volumes (>500mL) or when splashing is more probable. For HCL and nitric acid, check the manufacturer’s rating.
  • All handling of aqua regia should be done in a fume hood with glassware. Never take an aqua regia container out of the fume hood. To trap the hazardous gases, keep the sash as low as possible. Never elevate it higher than the recommended level (18 inches).
  • All work should be done in a secondary container that is devoid of organic waste and clean. Warning: Do not add organics to aqua regia as this can cause an explosion. Organic chemicals include acetone, isopropanol, ethanol, photoresist, and detergents, among others. Organics, even at tiny levels, may render the aqua regia liquid unstable.
  • Make tiny, fresh batches of aqua regia for each user for the greatest effects and safety.
  • Always add nitric acid to HCL while making aqua regia, never the other way around.

Procedures in Case of an Emergency

Contact with the skin

Rinse the injured skin thoroughly for approximately 15 minutes with plenty of water; if required, use the safety shower. Dispose of any infected clothes.

Eye Contact

Use the eyewash to completely cleanse the eye for at least 15 minutes, raising and rolling the upper and lower eyelids as needed.

Inhalation

Get out into the fresh air as soon as possible.

Ingestion

Do not force yourself to vomit. Using water, rinse your mouth.

Seek medical help if any symptoms continue following the first aid techniques. Provide the medical team with the hydrochloric and nitric acid Safety Data Sheets (SDS).

Spills

Sodium bicarbonate or another acid neutralizer should be used to neutralize spills right away.

Storage

WARNING! A stoppered bottle of aqua regia should never be stored—it might explode! Fresh aqua regia should be produced before each usage, and any leftovers should be neutralized as soon as possible.

Frequently Asked Questions(FAQs), “Is aqua regia flammable?”

What makes aqua regia so hazardous?

Aqua regia may be formed when nitric and hydrochloric acid mixtures react, generating poisonous nitrosyl chloride (yellow to deep red) gas. The act of inhaling is corrosive! Inhaling vapors may induce respiratory problems, pneumonia, and respiratory failure, each of which can be deadly.

What is the best way to get rid of aqua regia?

Disposal. Pour any leftover aqua regia into a big container of ice.  Until the pH is neutral, neutralize the mixture with an aqueous basic solution, such as 1M or 10percent sodium hydroxide or sodium bicarbonate (NaHCO3) in water.

Is it possible to keep aqua regia?

Always add nitric acid to HCL while making Aqua Regia, never the other way around. Aqua regia should never be stored Aqua Regia soon loses its potency owing to the oxidation of its reactive components, in addition to its toxic byproducts and reactions. For each usage, create a new solution.

What is aqua regia and how does it work?

Aqua regia is a solution of nitric acid and HCL in a 1:3 molar ratio. Aqua regia has the ability to dissolve noble metals like gold and platinum, but not all metals. Chloroauric acid is manufactured primarily using aqua regia.

Is it true that aqua regia dissolves glass?

The glass will not dissolve in aqua regia. Because glass is chemically robust, it is often used to store and transport corrosive and oxidizing compounds, as well as to line reaction containers holding these materials.

What is aqua regia pH level?

Aqua regia is a yellow-orange bubbling liquid called by alchemists for its ability to dissolve noble metals such as gold and platinum, but not all metals. Its pH value is virtually 0 since it is a blend of concentrated acids.

What’s the best way to clean my aqua regia glasses?

Label the bottle “Aqua Regia, 3-1 HCL/nitric acid solution,” then write your name and the date on it. Soak the glass substrates for thirty min in the bath. Soak for many hours for extremely clean surfaces. Rinse with DI water before blow-drying.

References:

https://www.ehs.harvard.edu/node/8270#:~:text=A%20very%20strong%20oxidizer.,severe%20burns%20and%20eye%20damage.
https://ehs.princeton.edu/laboratory-research/chemical-safety/chemical-specific-protocols/aqua-regia
https://cameochemicals.noaa.gov/chemical/4079
https://drs.illinois.edu/Page/SafetyLibrary/AquaRegia
https://www.vanderbilt.edu/vinse/facilities/safety_data_sheets/Aqua_Regia.pdf
https://www.concordia.ca/content/dam/concordia/services/safety/forms/EHS-DOC-227_Aqua_Regia_Safety_Guidelines_V1.pdf

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