General Chemical Procedures | Faculty of Engineering and Natural Sciences

his section covers frequently used highly hazardous chemicals and provides detailed information on their handling, storage and disposal.

Aluminum Chloride (anhydrous)

Overview

Anhydrous aluminum chloride (aluminum trichloride, AlCl3) is an odourless, white or yellow crystalline solid. Reaction of AlCl3 with water violently liberates hydrogen chloride (HCl) gas. AlCl3 readily sublimes to yield HCl(g) at 178 oC. Both solid and gas byproducts are highly corrosive to eyes, skin and mucous membranes. AlCl3 is considered as incombustible; however, it is strongly advised not to use ABC or BC type fire extinguishers.

Handling

Working with AlCl3, wear safety glasses, impervious gloves and a fire-retardant laboratory coat. Keep ignition sources under control and try to avoid dust formation. Avoid contact with water or moisture. Always keep dry sand available in the working area and make sure that there is a Class D extinguisher available nearby. When large quantities of AlCl3 are to be used, make sure to work on a dry bench, preferably in a fume hood or glove box. Avoid contact with water and moisture.

AlCl3 is incompatible with strong oxidizers and caustics, hydrated reagents, alcohols, sodium oxide, ethylene oxide, nitromethane and a wide variety of other materials. AlCl3 corrodes transition metals.

Always heat AlCl3 in a proper containment for generated HCl(g). Treatment of AlCl3 with water or heat yields an exothermic reaction where hydrogen chloride gas is released.

Storage

Tightly seal AlCl3 storage containers and keep in a cool dry place separated from other combustible materials. Storage containers may pressurize upon water contamination.

Disposal

Store wastes in tightly sealed containers. Dispose as hazardous waste.

Aqua Regia

Overview

Aqua regia (Latin for "Royal Water") is nitrated hydrochloric acid solution. It is prepared by mixing hydrochloric acid and nitric acid in a ratio of 3:1, respectively. It is generally employed to remove metals such as gold, platinum and palladium from substrates; therefore it is widely used in microfabrication and microelectronics labs. It also helps to remove trace amount organic compounds from glass. Aqua regia solutions are extremely corrosive and may result in explosion or skin burns if not handled with extreme caution.

Handling

Aqua regia melts plastics and corrodes most metals. Always use glass (preferably Pyrex) containers.
Do not store aqua regia solutions. Mix up only the amount you need, then dispose right after use.
Prepare the solution in hood and lower the sash as much as possible. Wear PPE such as chemical splash goggles, face shield, lab coat and appropriate gloves.
Always add the nitric acid to the hydrochloric acid slowly.
While working with aqua regia, always use a fume hood since dissolving metals in aqua regia result in toxic gases release.
Aqua regia solution is highly energetic and possesses explosion risk. It is very likely to become more than 100 oC. Be careful while handling.
An exothermic reaction takes place upon adding acids or bases to aqua regia, or spraying water on it.
Leave the hot aqua regia solution cooling in an open container and do not remove/replace until it is cooled.
Do not store aqua regia in a closed container since it oxidizes over time to form toxic gases such as nitrosyl chloride, nitrogen dioxide and chlorine. Therefore, the container gets pressurized, likely causing an explosion.
Be aware of the risk that mixing aqua regia with organic compounds may cause an energetic reaction, i.e. explosion.

Storage

Do not store aqua regia since its reactive components readily oxidize and lose effectiveness. Prepare a fresh solution prior to each use. Neutralize excess solution with sodium bicarbonate and then drain-dispose by flushing with large amount of water.

Disposal

Aqua regia is disposed via drain by flushing with copious amounts of water once the material has cooled and neutralized with sodium bicarbonate. On the other hand, if there’s heavy metal contamination (i.e. silver, chromium) in aqua regia then the neutralized solution should be collected as hazardous waste.

Hydrofluoric Acid

Hydrofluoric acid is an aqueous inorganic acid solution commonly used in research and industry due to its etching property of silicon compounds. It is a fundamental tool in semiconductor and electronic fabrication, mineral processing and glass etching. Besides these useful properties, hydrofluoric acid poses serious health risks upon exposure. Therefore, safe handling and usage practices should be reviewed prior to use and continuously applied while working with this material.

The Technical Info:

Hydrofluoric acid (CAS#7664-39-3) is the aqueous form of hydrogen fluoride gas with a molecular weight of 20.01 g/mole and both versions are referred to as HF in general use. It is miscible with water and is usually found in concentrations of 48-52% in water. 0.1 M aqueous solution of HF has a pH at approximately 1.0. Hydrofluoric acid is so corrosive that unlike other mineral acids, it attacks glass, concrete, rubber, quartz and alloys containing silica.

If you have to use Hydrofluoric acid, please contact and inform LS/LSS beforehand.

Why So Dangerous?

There is a risk of surface burns due to exposure of mineral acids including hydrochloric, phosphoric, nitric and sulfuric acid. This may result in local tissue corrosion caused by acid’s hydrogen cation activation. Effect of exposure to these acids is usually local focused on the area affected by acid.

On the other hand, hydrofluoric acid does not only cause local injuries but it also does not stop there. The skin rapidly absorbs free fluoride anion and the damage propagates inside, penetrates into non-surface body tissues, resulting in systemic injury.

In addition, the affinity of fluoride anion against essential minerals of body health; calcium and magnesium. Fluoride readily binds to calcium in blood, consuming body reserves of this mineral. It also attacks bone structure and forms calcium fluoride salt. A condition called hypocalcaemia, i.e. organ failure takes place due to depletion of serum calcium levels. Thus, heart functions become disordered and the heart eventually fails, resulting in death.

Another notable peculiarity of hydrofluoric acid is that the local dermal burns caused by hydrogen cation may not be as painful as the other acids, making the exposure harder to feel from warning properties. One may not feel any symptoms for 1 to 8 hours following skin contact with a concentration range of 20% to 50% hydrofluoric acid. This latency period will elongate to 24 hours as the concentration drops to less than 20%. Without medical care, a skin contact of 10 % of total body with 1-2% hydrofluoric acid results in death, but dermal burns are not likely to be immediate.

Hydrofluoric acid in moderate concentrations tends to fume releasing HF gas. When exposed to air, this gas produces additional health risks by inhalation.

Signs and Symptoms of Exposure

Skin Exposure – High HF concentrations, particularly anhydrous HF causes severe burns and an immediate pain and a visible white color occurs around the contact area, which eventually forms blisters. Dilute solutions of HF bring redness, swelling and blistering symptoms followed by acute throbbing pain.

Eye Contact – HF causes severe burns in eyes resulting in opacification, even destruction of the cornea. This may lead to blindness if not treated.

Inhalation – HF inhalation may cause several acute symptoms including coughing, choking, chest tightness, chills, fever and cyanosis (blue lips and skin). In case if you suspect of having exposed to HF by inhalation, seek medical attention as soon as possible and get further pulmonary effects observed by physicians. This is also valid for people exposed with HF around head, neck or chest areas. Significant inhalation exposure is not likely if there’s no upper respiratory system irritation is observed.

Ingestion – Ingestion of even a very small amount of dilute HF results in death by severe burns in mouth, esophagus and stomach.

What to Do if You Are Exposed to HF

Time is of the essence as exposure to HF is a life-threatening emergency. Delay in first aid or medical treatment will result in greater damage or possibly death.

Skin Contact

It is of primary importance to wash the acid off quickly and thoroughly. Even before taking contaminated clothes off, immediately start washing under a safety shower.
The affected area should be flushed off for 5 minutes with plenty of water.

Begin the following procedure right after rinsing:

Apply 2.5% calcium gluconate topical gel on affected skin area and massage. It should be noted that, the person applying calcium gluconate gel shuld wear gloves to prevent secondary HF exposure.
Apply iced 0.13%Benzalkonium chloride (Zephiran®) solution soaks or compresses.
Ask professional medical care right after first aid.

Eye Contact

Wash the eyes with plenty amount of lightly flowing water and apply hexafluorine.
Apply ice water compress during transportation to hospital.

Inhalation

Immediately move victim to fresh air and call health center (7666).

Ingestion

Drink large amounts of water as quickly as possible to dilute the acid. Do not induce vomiting. Do not give emetics or baking soda. Never give anything by mouth to an unconscious person.
Drink several glasses of milk or of milk of magnesia, Mylanta®, Maalox®, etc. or grind up and administer up to 30 Tums™, Caltrate™ or other antacid tablets with water.

Personal Protective Equipment

The best medicine in working with hazardous chemicals as hydrofluoric acid is prevention. When working with HF, following personal protective equipments should be worn in most (but not all) cases:

Gloves – particularly Polyvinyl Chloride (PVC) or Neoprene gloves. A suitable size should be selected for each individual. In case of working with large amounts or if there’s a risk of immersion of hands, Gauntlet style gloves are advised.
Shoes – closed toe, preferably made up of leather or durable non-porous material. Rubber boots or over-boots should be worn when working with large amounts.
Lab coat – preferably rubber or impermeable material, must be in a full-length and full arm construction. Please consult to LS/LSS to get the necessary PPE.
Eyewear – Chemical splash goggles should be worn at all times.
Ventilation – Fume hood use is obligatory.

Storage, Use, and Disposal

Hydrofluoric acid rapidly attacks silica-containing materials, including glass. It can best be stored in polyethylene containers. HF storage requires secure capped bottles and lids providing a gas-tight seal to prevent HF gas leaks. Hydrofluoric acid is never disposed of by drain even though it was neutralized. In case of neutralization, drain disposal is not advisable even if the resulting solution is at neutral pH (7.0). Since the neutralization of HF produces toxic metal fluoride salts, it should always be collected as hazardous waste and kept in plastic bottles. Universal adsorbent material, such as spill pillows, may be used to absorb small spills of hydrofluoric acid (<100 mL). For major spills of hydrofluoric acid (100 mL to 4 L) HF resistant spill materials must be used to soak up since spill pillows may degrade easily. Make sure that you are wearing the appropriate personal protective equipment and gear and have calcium gluconate around when you are cleaning an HF spill.

Along with the spill area, all equipment contaminated with hydrofluoric acid poses high risk and should be disposed of along with other hazardous waste. These equipment include research tools, empty containers previously containing HF, spill debris and personal protection equipment worn.

Lithium Aluminum Hydride

Overview

Lithium alumium hydride (LAH) is a chemical rapidly reacts with water, acids and oxygen-containing compounds. It is an odourless solid can ignite in moist air due to friction or static sparks. Conventional fire extinguishers of ABC and BC should never be used to fight an LAH fire since they may intensify the fire. LAH is corrosive and may cause complications in eyes, skin and mucous membrane.

Handling

Safety glasses, impervious gloves and fire-retardant laboratory coats should always be worn while handling LAH. Ignition sources should always be kept under control to prevent fire. Contact with water should also be avoided. It is advised to keep dry sand and a class D extinguisher immediately available while working with LAH.

An inert gas atmosphere, such as argon or nitrogen, should be ensured while working with large amount of LAH in powder form. As a personal safety measure, one should work with LAH under fume hood or glove box.

LAH is incompatible with several chemicals including alcohols, transition metal salts, oxidizing agents, and a wide variety of other materials. On the other hand, LAH reacts violently on contact with powerful oxidizers.

Never grind LAH nor heat it. LAH releases hydrogen gas via an exothermic reaction when in contact with water, acids or when heated.

Storage

LAH should be separated from combustible materials and be stored in tightly sealed containers.

Disposal

Waste LAH should be stored in sealed containers and be disposed as hazardous waste.

Phenol

Overview

The major hazard of phenol is its ability to penetrate the skin rapidly, causing severe burns. Toxic and even fatal amounts of phenol can be absorbed through relatively small areas of skin. Due to its local anesthetizing properties, skin burns may be painless. Phenol may be fatal if swallowed, inhaled or absorbed through the skin.

Since phenol easily penetrates leather, care should be taken not to walk in spill areas.

Handling

In case if there’s a splash risk wear chemical splash goggles and/or a face shield. Wear personal protective equipment such as impervious clothing including close-toed shoes, lab coat or apron and butyl rubber or neoprene gloves. Since hot liquid phenol attacks aluminium, lead, zinc and magnesium, avoid heat sources, flame and ignition.

Storage

Phenol must be isolated from heat or ignition sources and be stored in a cool, dry and ventilated area. It must also be separated from combustible or reactive materials and kept safe from direct sunlight.

Disposal

All phenol and phenol-contaminated materials should be disposed of as hazardous waste.

Phosphorus

Overview

Amorphous (red) phosphorus is not considered as toxic in pure form. It is a reddish-violet powder and mostly stable under ordinary conditions. However, it may fire easily when exposed to excessive shock or friction.

Yellow phosphorus, considered as contaminant in red phosphorus, is a rather more hazardous form of the material. It is in fact an allotrope of phosphorus and is extremely toxic with an estimated human lethal dose of 50-100 mg. Yellow phosphorus is spontaneously combustible when exposed to air; therefore it must be stored under water.

It is strongly advised to take precautions against yellow phosphorus risks while handling or working with amorphous phosphorus.

Handling

Safety glasses, impermeable gloves and a fire-retardant laboratory coat should always be worn while working with phosphorus.

Safety glasses, impermeable gloves and a fire-retardant laboratory coat should be worn all the time. Ignition sources must be kept under control and dust formation be avoided, along with heat, shock and friction. It is advised to keep dry sand and a class A water/wet foam extinguisher immediately available while working.

In case if large amount of phosphorus will be used, it is strongly advised to work in an inert atmosphere, particularly glove box.

The two allotropes of phosphorus form toxic phosphine gas upon exposure to alkalis. They are incompatible with halogens, halides, sulphur and oxidizing materials as well.

Storage

Keep red phosphorus separated from incompatible materials mentioned above and store in a cool dry place in tightly sealed containers. Yellow phosphorus, along with contaminated red phosphorus, must be kept under water and sealed to avoid exposure to air.

Disposal

Store wastes (under a layer of water) in tightly sealed containers. Dispose as hazardous waste.

Phosphorus Trichloride

Overview

Phosphorus trichloride (phosphorus chloride, PCl3) is a colorless fuming liquid easily react with most of the organic compounds. It also rapidly react with water and yield phosphoric acid and hydrogen chloride (HCl) gas. It is a strong oxidizer and highly corrosive to eyes, skin and mucous membrane along with its by-product.

Handling

PCl3 gives an exothermic reaction with water, releasing acid gases. Personal protective equipment involving safety glasses, impervious gloves and a fire-retardant laboratory coat should be worn while working/handling. Ignition sources must be kept under control and water contact must be avoided. It is strongly advised to keep a dry sand supply and a class D extinguisher available around the working area.

Dry surroundings, preferably glove box must be used while working with large amounts of PCl3. Water-containing or humid environments must be avoided. PCl3 makes most of the transition metal corroded especially in humid environment. Incompatibility list of PCl3 includes most of the organics, fluorine, and lead oxide along with many other substances.

PCl3 should not be heated without a proper container dedicated to and durable of acids, particularly hydrochloric and phosphoric acid. It may release gaseous phosphine and diphosphine in thermal decomposition.

Storage

Keep PCl3 separated from combustibles and store in a cool dry place in tightly sealed containers. It is advised to use pressurized containers in case of water contamination.

Disposal

Store wastes in tightly sealed containers. Dispose as hazardous waste.

Piranha Solutions

Overview

Piranha solutions are widely used in microfabrication labs for cleaning purposes to remove organic residues. It is prepared by mixing 3:1 of sulphuric acid and hydrogen peroxide (30%), respectively. Mixing may be carried out either beforehand or during the application to the material. In that case, sulphuric acid should be applied before peroxide.

Piranha solutions are energetic materials may easily cause explosion. It is also quite probable to cause thermal burns if not handled safely. When exposed to its vapor, respiratory system may be irritated.

Handling

Glass containers, preferably Pyrex®, should be used all the time since plastic containers may be degraded when in contact with piranha solutions.
Label all piranha solution containers properly.
Prepare piranha solution in a fume hood by keeping the sash between you and solution as low as possible. Appropriate PPE, such as acid resistant lab coat and/or apron with sleeve covers, gloves (butyl) and chemical splash goggles should be worn at all times.
Hydrogen peroxide should be added to sulphuric acid by gentle stirring. Never add sulphuric acid before hydrogen peroxide.
It is advised to keep the peroxide concentration under 30%. Do not exceed 50%.
While preparing, piranha solution becomes extremely hot, exceeding 100 °C. To avoid thermal injuries, do mind the personal protective measures.
Piranha solutions should never be mixed with organic compounds, as it is incompatible with them. Do not mix with bases either, including photoresist. It may cause to an explosion to mix piranha solution with incompatible materials.
Piranha solutions are intended to clean residual compounds, therefore make sure that the containers are all washed, rinsed and dried beforehand.
When in contact with equipment to be cleaned, it takes time to stabilize the solution. Thus, immerse equipment one by one, slowly and carefully.
Do not store fresh piranha solution in closed containers, not even partially closed.
Allow piranha solution react with equipment overnight. Label the container and leave open in a fume hood until disposal.

Storage

As it is quite reactive, piranha solution cannot be stored before use. Prepare fresh solutions every time as needed. Excess or used piranha solutions should be disposed following the procedures below.

Disposal

Piranha solution is sent to disposal only if it was fully reacted, the cooled and all the gases were allowed to release.

Small amounts of piranha solution (>100 mL) should be neutralized. Note that, this process releases energy and must be cooled in an ice bath to control the temperature and prevent heating. Neutralization can only be done with acid resistant lab coat and/or apron with sleeve covers, gloves (rubber or butyl) and chemical splash goggles and only under hood. The solution should be diluted to less than 10% prior to neutralization. Once diluted, bases such as sodium hydroxide or sodium carbonate should be added very slowly with effective stirring. This process is done until the pH reaches to a range between 4 to 10. After this point, resulting solution may be disposed of via drain. Using carbonates as neutralizing agent may cause to bubbling and foaming and this may create some additional risks of splash and spill.

If the amount to be disposed is higher than 100 mL, used piranha solutions are collected as waste in an acid bottle (empty sulphuric acid bottle, for example). Doing this, a small amount of waste piranha solution should be added to bottle in order to check if there’s any residual materials left in the container. If no reaction takes place, then the rest of the solution may be slowly transferred to bottle. Waste piranha solution containers must be labelled. Waste piranha solutions should not be combined with any other waste.

Potassium

Overview

Potassium is a silver-colored metal that is odourless and highly corrosive to eyes, skin and mucous membranes. Highly unstable peroxides may form if potassium is stored for a long time. It rapidly reacts with water, acids and oxygenated compounds and may ignite in moist air or due to friction or static spark. Water and conventional ABC fire extinguishers should never be used since they may intensify the fire.

Handling

Safety glasses, impervious gloves and a fire-retardant laboratory coat should be worn all the time while working with potassium. Any contact with water or moist must be avoided. It is strongly advised to keep a dry sand and class D type fire extinguisher available around when you work with potassium.

An inert atmosphere such as argon or nitrogen must be maintained when large amounts of potassium are to be used.

Note that potassium is incompatible with alcohols, oxidizing agents, hydrated salts, acids and many other chemicals, therefore it must be stored separately from these chemicals. It is also oxidized rapidly.

Potassium should not be grinded or heated. Any contact with water and incompatible chemicals results in an exothermic reaction where hydrogen gas is released that is highly flammable. In addition, oxidized potassium poses a risk of explosion upon handling.

Storage

Potassium should be kept in dry toluene, kerosene and/or under an inert atmosphere of nitrogen or argon. Storage requires tightly sealed containers and a cool and dry environment, rather well separated from combustibles. Unused potassium should not be stored more than one year in any condition.

Disposal

Waste potassium should be stored in toluene or kerosene by tightly sealing the container. It should be disposed of as hazardous waste.Superoxide or peroxide derivatives should never be handled. A white precipitate identifies contamination of those materials.

Sodium

Overview

Sodium is a silver-white-colored metal that is highly corrosive to eyes, skin and mucous membranes. It rapidly reacts with water, acids and oxygenated compounds and may easily ignite in moist or dry air above 115 oC. Water and conventional ABC fire extinguishers should never be used since they may intensify the fire.

Handling

Safety glasses, impervious gloves and a fire-retardant laboratory coat should be worn all the time while working with sodium. Ignition sources must be kept under control and dust formation should be avoided. Any contact with water or moist must be avoided. It is strongly advised to keep a dry sand and class D type fire extinguisher available around when you work with sodium.

An inert atmosphere such as argon or nitrogen must be maintained in a fume hood when large amounts of sodium are to be used.

Note that sodium is incompatible with oxygen, carbon dioxide, halogens and halogenated solvents, alcohols, oxidizing agents, hydrated salts, acids and many other chemicals, therefore it must be stored separately from these chemicals. It is also oxidized rapidly upon contact with oxidizers and/or water.

Sodium should not be grinded or heated. Any contact with water acids or alcohols results in an exothermic reaction where hydrogen gas is released that is highly flammable. Hydrogen gas is also released in the presence of dry air above 115 oC.

Storage

Disposal

Sodium waste should be stored in tightly sealed containers under toluene or kerosene. Dispose as hazardous waste.

Sodium Amide

Overview

Sodium amide (NaNH2) is a greyish-white powder that is highly corrosive to eyes, skin and mucous membranes. It has a slight odor of ammonia. It rapidly reacts with water, acids and halogenated compounds and may easily ignite in moist or dry air above 450 oC. Water and conventional ABC fire extinguishers should never be used since they may intensify the fire.

Sodium amide forms peroxides that are sensitive to shock. These peroxides poses a high risk of explosion upon contact with air, heat or if stored for a long time. Residual sodium amide should be immediately disposed.

Handling

An inert atmosphere such as argon or nitrogen must be maintained in a fume hood or glove box when large amounts of sodium amide are to be used.

Note that sodium amide is incompatible with oxygen, carbon dioxide, halogens and halogenated solvents, alcohols, oxidizing agents, hydrated salts, acids and many other chemicals, therefore it must be stored separately from these chemicals. It is also oxidized rapidly upon contact with oxidizers and/or water.

Sodium amide should not be grinded or heated. Any contact with water acids or alcohols results in an exothermic reaction where hydrogen gas is released that is highly flammable. Peroxide derivatives can easily explode upon handling.

Storage

Potassium should be kept under an inert atmosphere of nitrogen or argon. Storage requires tightly sealed containers and a cool and dry environment, rather well separated from combustibles. Unused sodium amide should not be stored for more than one year.

Disposal

Sodium amide waste should be stored in tightly sealed containers under dry inert atmosphere. Deactivation of used material can be carried out under well controlled environment. Dispose as hazardous waste. Containers of peroxide derivatives should never be handled. Yellow or brown solids identify a contamination of these materials.

Explosives

Overview

An explosive is defined as a chemical that undergoes a rapid chemical transformation when subjected to heat, impact, friction, detonation, or other suitable initiation, evolving large amount of gases as a result and significantly exerting the pressure of surroundings. It can either be found in a form of chemical compound or a mechanical mixture. The term explosive also applies to materials that either detonate or deflagrate.

Handling

Great care must be taken upon handling explosives, particularly peroxide formers. Container bottles should be visually inspected for any residual peroxide crystals.

The scale of work is critical. Explosives should be used/worked with at the smallest scale possible (e.g., mmole) and scale-up should only be taken care with the authorization of the supervisor.
Eliminate the confinement sources in case if you work with materials that easily deflagrate.
There must be no additional chemicals around the working area while working with explosives.
Static discharge sources should be eliminated since they may initiate certain type of explosives. Note that low humid air enhances the risk of static discharge. Nonstatic wipes and brushes must be used. If not, appropriate wet methods should be selected cleaning.
All transfer operations should be conducted using compatible equipment. Note that certain explosives may form more sensitive compounds when in contact with metals.
Working area, along with all the equipment and tools used should always be kept clear. Explosives should not be scraped from any surface.
Never crush or grind and explosive, nor apply pressure.

Storage

Explosives should be stored in designated cabinets. Flammables should be stored in designated cabinets or refrigerators approved for flammable storage.

Newly arrived containers of explosives should be labelled with receipt date. Reactive materials cannot be used past their expiration date.

Disposal

Explosive waste should be collected as hazardous waste. Explosive compounds are more stable when diluted. Therefore, they are diluted using a safe solvent if possible. Explosive waste must be separated from other wastes.

Flammables

Overview

Flammable liquids are defined as liquids having a flash point below 38 oC.
Combustible liquids are defined as liquids having a flash point at or above 38 oC and no greater than 93 oC.
Flash point is the minimum temperature at which vapors are formed on the surface of a substance in sufficient quantity to ignite when exposed to an ignition source.
Fire point is the minimum temperature at which self-sustained combustion of a substance will occur upon or after exposure to an ignition source.
Boiling point is the temperature at which the vapor pressure of a liquid equals the atmospheric pressure and the liquid transforms into a vapor.
Auto-ignition temperature is defined as the minimum temperature at which self-sustained combustion will occur in the absence of an ignition source.
Lower explosive limit (LEL) stands for the lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source (arc, flame, heat).
Upper explosive limit (UEL) stands for highest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source (arc, flame, and heat).

Handling

Flammable liquids must be stored in a designated area such as a flammable storage cabinet.
Large amounts of flammable liquid (more than 37 liters) are not permitted to be stored outside a flammable cabinet.
Flammables should not be over-purchased; one should only purchase them amount that can be safely stored regarding the facility capacity.
Any contact with skin, eyes, and inhalation should be avoided.
Flammables must be kept away from ignition sources.
Containers must be kept tightly closed. Storage requires a cool, dry, and well-ventilated area away from incompatible substances such as oxidizers.
Follow LS/LSS’ instructions for PPE, which may differ depending on the type and/or quantity of flammable/combustible liquid being used.
They should be used in the smallest quantities possible for the experiment being performed.
Work must be conducted in a chemical fume hood if air concentrations above 10% of the LEL could be created, if the chemical is irritating to the eyes or respiratory system, and/or is toxic by inhalation.
When not in use, containers should always remain closed. This is the main precaution to prevent release of flammable vapor and/or unintended ignition.
Containers should be labelled properly.
If not used, they must be stored in designated flammable storage cabinets.
Containers of flammables must be compatible with the material stored inside.
Using ignition sources (flame burners or any open flame source, hot plates, electrical equipment with frayed or cracked wiring, etc.) and/or creating static electricity around the flammable/combustible chemicals should be avoided.
Containers must be grounded and bonded upon transfer of large amounts (more than 4 liters) of flammable/combustible liquids.
All flammable/combustible liquids should be transported in secondary containment, such as polyethylene or other non-reactive acid/solvent bottle carrier.
Flammable/combustible liquids must be segregated from incompatible materials such as oxidizers (e.g., hydrogen peroxide, nitric acid).
In case if flammable liquids are to be stored in refrigerators or freezers, these should be specially modified or designated “flammable-safe” refrigerators and freezers which does not pose a risk of ignition due to the internal light or thermostat circuit.

Water-Reactives

Overview

Water reactive materials can react violently with water or atmospheric moisture to produce gas and heat. The risks associated with a specific chemical depend on its reactivity and the nature of the gaseous product (flammable, toxic, or both). The mutual production of flammable gas and heat can lead to spontaneous ignition or explosion. Typical gases produced are: H2, CH4, H2S, NH3, PH3, HCN, HF, HCl, HF, HI, SO2, and SO3. Prior to working with any water reactive chemicals you must identify which gas may be formed in case of exposure to water and learn the risks associated with this gas.

The reaction rate of solid material (and therefore heat and gas generation) depends on the material's surface area. Therefore smaller particle size increases the hazards associated with these materials.

Handling

Unless it is known otherwise, assume the material is pyrophoric.
To be handled always in a glove box or under inert atmosphere.
Design a quenching scheme for residual materials prior to using water reactive materials.
Never use water to quench the material itself or a reaction where a water-reactive reagent is used.
Begin quenching with a low reactivity quenching agent and slowly add more reactive quenching agents. For example, first quench residual sodium metal with isopropanol and then add ethanol to the mixture.
Design your experiment to use the least amount of material possible to achieve the desired result.
It is better to do multiple transfers of small volumes than attempt to handle larger quantities. Before transferring, make sure that the material is at room temperature.
Avoid formation of dusts and aerosols.
Provide appropriate exhaust ventilation at places where dust is formed.
Take measures to prevent the build-up of electrostatic charge.
Keep away from sources of ignition – open flames (e.g. Bunsen Burner).
Eliminate or substitute a less hazardous material when possible.
Verify your experimental set-up and procedure prior to use.
Inform colleagues that this material will be used and where. Label the work area with a sign saying “Water Reactives Use Area”.
Only use if the area is properly equipped with a certified eye wash/safety shower within ten seconds of travel.
Never use water to extinguish fires caused by water reactive materials.

Storage

Never allow contact with water.
Always handle inside a glove box.
Over time, pressure may increase causing containers to burst. Keep container tightly closed in a cool, dry, well-ventilated place and protected from sunlight.
Store and handle under inert gas (Inert gases such as nitrogen, argon etc.)
Keep in a dry place (such as a desiccator or a dry box or glove box) free of moisture/humidity.
Store away from heat sources and in a flameproof area.
Do not leave the container near a lab sink, emergency eyewash or safety shower.
Store in a location, separated from acids, oxidizing and other incompatible materials.
Use/purchase only amount that is needed in a reasonable amount of time. Use small quantities whenever possible.
Store in a separate secondary container and label the material clearly.
Minimize dust generation and accumulation.
Hazard communication label on the container must read “Water Reactive”.
Never allow product to get in contact with water or water-based compounds during storage.
Do not leave the container on the benchtop - even momentarily.
Follow any substance-specific storage guidance provided in safety data sheet documentation.
Monitor your inventory closely to assure that you have tight control over your material.
Wash hands and arms with soap and water after handling.
Minimize dust generation and accumulation.
At the end of each project, thoroughly inspect the area for residual reactive material.

Oxidizers

Overview

Oxidizing chemicals are materials that spontaneously evolve oxygen at room temperature or with slight heating or promote combustion. This class of chemicals includes peroxides, chlorates, perchlorates, nitrates, and permanganates. Strong oxidizers are capable of forming explosive mixtures when mixed with combustible, organic or easily oxidized materials.

Handling

Do not store with incompatible material.
Do not store with flammables or combustibles.
Review SDS for specific storage conditions.
Chemicals shall not be drain-disposed unless prior approval is given by LSS/LS.
Excess oxidizers and all waste material containing oxidizers must be placed in a container labelled with the following “Hazardous Waste Oxidizers”, and the full chemical name.

Storage

Oxidizers should be stored in a cool and dry location. Keep oxidizers segregated from all other chemicals in the laboratory. Minimize the quantities of strong oxidizers stored in the laboratory. Never return excess chemicals to the original container. Small amounts of impurities may be introduced into the container, which may cause a fire or explosion.

Disposal

All materials contaminated with oxidizing chemicals pose a fire hazard and should be disposed of as hazardous waste. Do not let contaminated wastes remain in the laboratory overnight unless proper containers are provided.

Peroxide Forming Compounds

Overview

Organic peroxides are a special class of compounds that have unusual stability problems, making them among the most hazardous substances normally handled in laboratories. In addition, certain laboratory chemicals can react with the oxygen in air to form peroxides. Some may continue to build peroxides to potentially dangerous levels, while others accumulate a relatively low equilibrium concentration of peroxides, which becomes dangerous only after being concentrated by evaporation or distillation. The peroxide becomes concentrated because it is less volatile than the parent chemical. Stabilizers or inhibitors are sometimes added to the liquid to extend its storage life, but distillation will remove the inhibitor.

Handling

Avoid friction, grinding, and all forms of impact near peroxides, especially solid peroxides. Do not use glass containers with screw caps or glass stoppers. Polyethylene containers with screw tops may be used.
Store peroxides at the lowest possible temperature consistent with their solubility or freezing point to minimize the rate of decomposition. Do not store them at or lower than the temperature at which the peroxide freezes or precipitates because peroxides in these forms are extremely sensitive to shock and heat.
Store all peroxidizable compounds in tightly closed, air-impermeable, light-resistant containers, away from light, heat, direct sunlight, sources of ignition, oxidizers, and oxidizing agents. Storage under nitrogen may be advisable in some cases.
Do not use metal spatulas to handle peroxides because metal contamination can lead to explosive decomposition. Magnetic stirring bars can unintentionally introduce iron, which can initiate an explosive reaction of peroxides. Teflon, ceramic or wooden spatulas and stirring blades may be used if it is known that the material is not shock sensitive.
Do not allow these compounds to evaporate to near dryness unless absence of peroxides has been shown.
Purchase peroxide formers with inhibitors added by the manufacturer when possible.
For peroxide forming compounds, mark the receipt and opening date on the container and discard within the time frame listed in the table above (or by the manufacturer’s expiration date, if listed on the container).

Disposal

Organic peroxides or peroxide forming compounds must be collected as hazardous waste.

Pyrophoric Compounds

Overview

Pyrophoric compounds are chemicals that, even in small quantities, are prone to ignition within five minutes after coming into contact with air.

Storage

Pyrophoric chemicals should be stored under an atmosphere of inert gas or under kerosene as appropriate. Do not store pyrophoric chemicals with flammable materials or in a flammable-liquids storage cabinet. Store these materials away from sources of ignition. Minimize the quantities of pyrophoric chemicals stored in the laboratory.

Never return excess chemicals to the original container. Small amounts of impurities may be introduced into the container, which may cause a fire or explosion.

Disposal

Never return excess chemicals to the original container. Small amounts of impurities may be introduced into the container, which may cause a fire or explosion. A container with any residual material must never be opened to the atmosphere. Attempt to use the entire reagent in your chemical reaction. If there is unused and unwanted material left over, place the bottle in a secondary container (preferably the original provided by manufacturer) in the satellite accumulation area for disposal by a licensed contractor and notify LSS for disposal.

References and sources for information from the relevant websites and documentation of different universities, NGOs and government agencies used in the preparation of this website are provided at references.