Laboratory Safety Guidelines

Guidelines for the Safe Use of Picric Acid

Following several inquiries, EHS has prepared a document entitled “Guidelines for the Safe Use of Picric Acid”. If you use picric acid, please ehs [at] mcgill.ca (email) us.

You can find a pdf version of the below document here: PDF icon Guidelines for the Safe Use of Picric Acid


Picric Acid (CAS 88-89-1), also known as 2,4,6-trinitrophenol, is a trinitro-aromatic compound related to trinitrotoluene (TNT) is used as a staining agent and reagent in laboratory procedures. The hazards associated with Picric Acid go beyond its acidic properties; it is unstable and has the ability to react with other materials and create explosive compounds.

Dry and dehydrated Picric Acid is an odourless bright yellow crystal; it is slightly soluble in water. It is highly unstable and highly sensitive to shock, heat or friction – it is a high-powered EXPLOSIVE. Dry Picric Acid can form very shock-sensitive, explosive picrate salts when in contact with concrete, amines, bases, and metals (copper, lead, mercury, and zinc); these unstable picrate salts are often more unstable and explosive than pure Picric Acid. When wet with 10% or more water, it is less hazardous.

Picric Acid that is wet with less than 30% water is an odourless, wet slurry of yellow crystals and has the consistency of wet sand and is DANGEROUSLY REACTIVE.

Picric Acid that is dry or wet with less than 30% water is classified as:

  • D1B - Poisonous and infectious material - Immediate and serious effects - Toxic
  • D2B - Poisonous and infectious material - Other effects - Toxic
  • E - Corrosive material
  • F - Dangerously reactive material

Picric Acid that is wet with more than 30% water is an odourless, yellow solution or wet slurry of yellow crystals and it is a FLAMMABLE SOLID. Wetted Picric Acid and solutions will lose moisture and become increasingly shock, friction and heat sensitive and may decompose explosively. Picric Acid can decompose at high temperatures and form irritating/toxic gases, such as nitrogen oxides. Explosive decomposition is likely if material is involved in a fire.

Picric Acid that is wet more less than 30% water is classified as:

  • B4 - Flammable and combustible material - Flammable solid
  • D1B - Poisonous and infectious material - Immediate and serious effects - Toxic
  • D2B - Poisonous and infectious material - Other effects - Toxic
  • E - Corrosive material

Health Hazards & Symptoms of Exposure

Picric Acid is TOXIC by all routes of entry. Picric Acid is CORROSIVE to the eyes and skin and may cause permanent eye injury and may cause scarring. It is considered an occupational SKIN SENSITIZER. Once sensitized, contact with even a small amount can cause an allergic reaction with symptoms such as skin redness, itching, rash and swelling. This reaction can spread from the hands or arms to other parts of the body. Picric Acid is harmful if swallowed.

Symptoms from Picric Acid exposure may include headache nausea, vomiting, diarrhea, abdominal pain, itching, urinary dysfunction, stupor, convulsions, death (liver and kidney damage may also occur) – the severity of the symptoms depend on the degree of exposure. Dermal exposure may cause irritation and can lead to allergic reactions; skin damage and staining at the contact site. Ingestion and absorption may cause poisoning.

First Aid Measures

Skin contact

  1. Immediately proceed to the nearest eyewash/shower and rinse the affected area thoroughly with water for at least 20-30 minutes. Remove all contaminated clothing while continuing to flush with water. If irritation persists, repeat flushing. DO NOT INTERRUPT FLUSHING.
  2. While the victim is rinsing the affected area, someone should call 911 for emergency medical assistance – if the 911 call is placed using a cellular phone, also call McGill Security Services (514-398-3000). At Macdonald campus, call McGill Security Services (514-398-7777).
  3. Transport victim to an emergency medical facility.

Eye contact

  1. Immediately proceed to the nearest eyewash station and flush the contaminated eye(s) with lukewarm, gently flowing water for at least 20-30 minutes. Hold eyelids open and away from the eye during irrigation to allow for thorough flushing.
  2. While the victim is rinsing their eyes, someone should call 911 for emergency medical assistance – if the 911 call is placed using a cellular phone, also call McGill Security Services (514-398-3000). At Macdonald campus, call McGill Security Services (514-398-7777).
  3. Continue to rinse affected area until emergency medical assistance arrives.

Inhalation

  1. Immediately move the victim to fresh air.
  2. If symptoms persist, obtain medical attention. Call 911 for emergency medical assistance – if the 911 call is placed using a cellular phone, also call McGill Security Services (514-398-3000). At Macdonald campus, call McGill Security Services (514-398-7777)

Ingestion

  1. Have the victim rinse mouth thoroughly with water.
  2. While the victim is rinsing their month, someone should call 911 for emergency medical assistance – if the 911 call is placed using a cellular phone, also call McGill Security Services (514-398-3000). At Macdonald campus, call McGill Security Services (514-398-7777).
  3. Do not induce vomiting. Have victim drink 240 to 300 ml (8 to 10 oz.) of water to dilute material in the stomach. If milk is available it may be administered after the water has been given.
  4. Transport victim to an emergency medical facility.

In all cases of accidental exposure, bring a copy of the Material Safety Data Sheet.

Emergency Eyewash & Emergency Shower

Both emergency eyewash and emergency shower are required within 10 seconds (approximately 55 feet or 16.8 meters) of any work with Picric Acid. They must be unobstructed and the emergency eyewash tested weekly.

Handling Information

Picric Acid is highly reactive with a wide variety of materials and easily forms picrate salts, which can be more reactive and shock sensitive than the acid. Metal picrates are extremely shock sensitive and will detonate with the slightest motion or vibration, they can be formed with metals such as copper, nickel, lead, iron and zinc. Calcium picrate is formed by the reaction of Picric Acid with concrete.

Before purchasing Picric Acid, consider the following:

  • Is there a less hazardous material that can substitute Picric Acid?
  • Is Picric Acid available in a solution form? Handling solutions decreases the risks considerably.
  • How long will it take to use up the quantity ordered? Do not order more than what can be used up in 6 months. Purchase on the smallest quantity that is necessary.

Before handling Picric Acid:

  • Read the Material Safety Data Sheet (MSDS) for Picric Acid – these guidelines do not substitute for the MSDS;
  • Identify work practices, engineering controls and protective equipment necessary to do the experiment safely, and include them in written lab procedures;
  • Ensure that engineering controls are operating and protective equipment is available;
  • Go through a dry run to identify potential hazards before using Picric Acid;
  • Be prepared for accidents - know the location of all safety equipment, including eyewash and the first aid kit, emergency contacts and phone numbers, and keep your coworkers informed about your activities with Picric Acid - Do not assume that all lab personnel know the hazards associated with the use of Picric Acid.

When handling Picric Acid:

  • Avoid direct contact - wear appropriate personal protective equipment (see below);
  • Work in a chemical fume hood when dispensing Picric Acid;
  • Do not break the seal on the container until the material is needed;
  • Visually inspect the container prior to use;
  • Do not use metal spatulas to remove the material from the container;
  • Before closing a container of Picric Acid, always clean the neck of the bottle, cap and thread with a wet cloth before recapping and seal cap with Parafilm;
  • Do not allow Picric Acid to come into contact with metal that is readily oxidized, and do not transfer the material to a container with a metal cap.
  • Never work alone when using Picric Acid.

Eye Protection: safety glasses

Protection Clothing: closed lab coat with sleeves fully extended to the wrist lab coat

Gloves:neoprene rubber and nitrile rubber when used for short periods only (resistance to breakthrough within 1 to 4 hours). Verify with manufacturer’s glove compatibility charts.

Safe Storage

If you have any questions about which protective clothing or gloves to purchase, contact EHS.

Picric Acid and its derivatives should be stored in small quantities in the original container in a cool, dry, well-ventilated area, out of direct sunlight and away from sources of heat. Protect from freezing temperatures. Store the original Picric Acid container in polyethylene secondary containers and store with other inorganic acids. Storage area should be made of fire-resistant materials. Storage area should be clearly identified, clear of obstruction and accessible only to trained and authorized personnel. Storage area should be away from work process and production areas, building and room exits or main aisles leading to exits. Post warning signs (available from EHS). Picric Acid is considered a flammable solid and is incompatible with oxidizers, reducing agents, inorganic salts, metals, alkaloids and albumin. Improperly managed or stored Picric Acid may become sensitive to shock, friction, and heat. In order to ensure that the quantity stored is as small as possible, keep your chemical inventory updated to reduce the potential for old and overlooked Picric Acid. Only use and store the least amount possible that the work requires.

Picric Acid must be stored with at least 10% moisture content and regular inspections must be made to ensure that the minimum moisture content is maintained. Picric Acid allowed to dry out to less than 10% water by volume becomes unstable and may pose an explosion hazard in your laboratory. Never let Picric Acid dry out. If the material appears dry, do not open or handle the container.

Keep Picric Acid in clearly labelled compatible containers (normally the shipping containers; include the date received). Place the original containers in polyethylene secondary containers, large enough to contain the entire contents of the original container. Label the secondary container with the following cautionary statement: "Keep Picric Acid immersed in water to maintain in a safe condition" and include the name and phone number of a contact person. Keep containers closed and do not stack.

Monitoring of Picric Acid Container

Picric Acid containers must be monitored regularly for evidence of crystallization or damage or leaks. Monitoring the containers monthly reduce the chances of explosive or drying out of solutions.

To monitor Picric Acid containers:

  • Attach a copy of the Picric Acid Inspection Log (See the pdf version of this document; link provided above)to the Picric Acid secondary container and write the date of initial receipt (see page 7).
  • After initially opening the container, inspect the material monthly to ensure that it contains enough water. The material should look like a wet paste. Document this inspection on the Picric Acid Inspection Log (See the pdf version of this document; link provided above) in the inspection column.
  • Rehydrate the contents of the container when necessary with deionised water to maintain a wet paste. Document this rehydration on the Picric Acid Inspection Log (See the pdf version of this document; link provided above) in the rehydration column.
  • Dispose of Picric Acid as a hazardous waste within two years of initial receipt.

Accidental Spills

If spilled outside a chemical fume hood, the spill must be cleaned by personnel trained to handle explosives:

  • Stop or reduce spill if it is safe to do so;
  • Evacuate the area and close the doors - restrict access to area and post a sign to prevent others from entering;
  • Call McGill Security Services (514-398-3000 Downtown Campus or 514-398-7777 Macdonald Campus).

If spilled inside a chemical fume hood, the spill can be cleaned by laboratory staff if they have the correct equipment, understand the hazards, know how to clean up the spill safely and dispose of the waste properly.

  • Stop or reduce spill if it is safe to do so;
  • DO NOT allow spilled material to dry - dampen spilled solids with water without stirring. DO NOT attempt to sweep up dry material. Picric Acid must remain wetted to reduce the hazard of cleanup;
  • Contain spill with material that does not react with spilled chemical - use a spill response pad or pillow damp with water to absorb spilled material;
  • Place pads or pillows in a compatible, impervious container with water added. Thoroughly wash the spill site after material pickup is complete;
  • Contaminated absorbent material may pose the same hazards as the spilled product;
  • Contact Hazardous Waste Management (514-398-5066 or www.mcgill.ca/hwm) and request an immediate pick-up of the containers of spilled product and contaminated absorbent material.

Disposal of Picric Acid

If:

  • An old container of Picric Acid is found;
  • There are crystals in the container;
  • The Picric Acid does not appear to be wet; OR
  • You cannot be determined what state the Picric Acid; Picric Acid should be disposed of as a hazardous waste within two years of initial receipt.

DO NOT TOUCH THE CONTAINER! Only experienced and knowledgeable personnel should handle Picric Acid in these situations - even a minor disturbance can be dangerous (crystals may have formed between the lid and the container). Attempting to open the container can result in an explosion.

Carefully inspect the container without moving it, looking for identification and an expiration date.

  • If there is the slightest indication of crystallization or low water level (it should look like a wet paste), contact McGill Security Services immediately (Downtown 514-398-3000; Macdonald Campus 514-398-7777). Secure the area, restricting access) and lightly mist any crystals on the outside of the bottle with a spray bottle containing water.
  • If there is no indication of crystallization or low water level, post a warning sign on the cupboard or area where the Picric Acid was discovered: “Potentially Explosive Picric Acid – Do Not Touch” and contact Waste Management Program (514-398-5066 or www.mcgill.ca/hwm) and request a chemical pick-up

Dry Picric Acid or picrate salts should not be touched or moved under any circumstances!


References:

Handling of Picric Acid by Laboratory Personnel (HSE Tool #22). Department of Health, Safety and Environment, University of British Columbia. Version 1/24/2005.

Safe Use and Management of Picric Acid (Safety Net #104). Environmental Heath & Safety, University of California Davis. Revision 11/06.

CHEMINFO Chemical Profile: Picric Acid, dry or wetted with less than 30% water. Canadian Centre for Occupational Health & Safety. Revision 2007-06-19.

CHEMINFO Chemical Profile: Picric Acid, wetted with not less than 30% water. Canadian Centre for Occupational Health & Safety. Revision 2007-06-19.

Guidelines for the Safe Use of Hydrofluoric Acid

Following an accident earlier this year that saw a graduate student hospitalized for a hydrofluoric acid burn, EHS has prepared a document entitled “Guidelines for the Safe Use of Hydrofluoric Acid”. If you use hydrofluoric acid, please ehs [at] mcgill.ca (email) us.

You can find a pdf version of the below document here: PDF icon Guidelines for the Safe Use of Hydrofluoric Acid


Hydrofluoric acid (HF; CAS #7664-39-3) is extremely corrosive and is used for many purposes including mineral digestion, surface cleaning, etching, and biological staining. HF is a clear and colorless liquid with a strong irritating odour at low concentrations (3 ppm). Aside from causing severe burns, HF is significantly more hazardous than many other acids since it can cause deep tissue damage and systemic toxicity. Prevention of exposure or injury is the primary goal when handling any chemical.

This document discusses the health and safety hazards of HF and how to protect yourself. Also included are emergency procedures for dealing with HF exposures, including important first aid treatment information. Special preventative measures for handling HF include:

  • Being aware of HF’s properties and dangers;
  • Being trained on the proper handling and safety precautions required when using HF;
  • Using appropriate engineering controls and ensuring that they are functioning properly;
  • Using the proper safety and personal protective equipment; and
  • Arranging to provide the appropriate first aid and medical treatment, if necessary.

WARNING: BURNS WITH CONCENTRATED HYDROFLUORIC ACID (HF) ARE USUALLY VERY SERIOUS, WITH THE POTENTIAL FOR SIGNIFICANT COMPLICATIONS DUE TO FLUORIDE TOXICITY. CONCENTRATED HF, LIQUID OR VAPOR, MAY CAUSE SEVERE BURNS, METABOLIC IMBALANCES, PULMONARY EDEMA AND LIFE THREATENING CARDIAC ARRYTHMIAS. EVEN MODERATE EXPOSURES TO CONCENTRATED HF MAY RAPIDLY PROGRESS TO FATALITY IF LEFT UNTREATED.*


Health Hazards

HF is very aggressive physiologically due to the fluoride ion that can readily penetrate the skin causing destruction of deep tissue layers and, unlike other acids which are rapidly neutralized, this process may continue for days if left untreated. The health hazards of HF are dependent upon the concentration, temperature and type and duration of exposure. You cannot dilute the hazards when working with HF and pH cannot be relied upon as an indicator of its potency.

Eye Contact

Eye exposure to HF may result in severe eye burns with destruction or clouding of the cornea. Blindness or permanent eye damage may result if untreated.

Skin Contact

  • HF readily penetrates human skin, allowing it to destroy and decalcify soft tissues and bone.
  • Skin exposure to concentrated HF (50%-100) immediately results in serious and painful destruction of tissue, often followed by blister formation; systemic fluoride poisoning may result.
  • Skin exposure at concentrations between 20% to 50% range may not produce clinical signs or symptoms for 1 to 8 hours.
  • Skin exposure at lower concentrations (typically <20%) may not produce pain or burning sensations until hours after the exposure (up to 24 hours).
  • HF’s ability to produce severe, delayed tissue damage without producing pain, means that all skin, eye, or tissue contact with HF should receive immediate first aid and medical attention, even if the exposure appears minor or no pain is felt.

Inhalation

Inhalation of HF vapour can seriously damage the lungs. Delayed reactions up to and including fatal pulmonary oedema (flooding of the lungs with body fluids) may not be apparent for hours after the initial exposure.

Safety Precautions for HF Use

Information and Training

Employees and lab personnel who handle HF must read the Material Safety Data Sheet (MSDS) and receive training from their supervisor or a qualified delegate (e.g., chief lab technician) on its hazards and what to do in the event of an exposure or a spill. The MSDS must be kept in the immediate work area where HF is handled and together with these Guidelines used for training.

Lab Ventilation

HF at concentrations greater than 5% must be handled inside a certified chemical fume hood to minimize inhalation of vapours.

Eye Protection

Chemical goggles together with a face shield are required when handling HF at concentrations greater than 20%. Safety glasses with side shields may not provide adequate eye protection.

Protection Clothing

A lab coat, a chemically-resistant apron and protective sleeves are required when handling HF at concentrations greater than 5%. No exposed skin is permitted. Protective clothing can be made of neoprene, fluorocarbon (viton) or other materials - consult the manufacturer’s chemical resistance data when selecting protective clothing.

Examples of protective clothing for use with 48% HF: Dupont® Tychem® QC

Gloves

Gloves should be dedicated for HF use only and must be inspected prior to use; even a pin-hole leak thorough gloves may result in exposure. If gloves become contaminated with HF, remove them immediately, thoroughly wash your hands, and check your hands for any sign of contamination. Contaminated gloves must be disposed of as HF waste. A second pair of nitrile exam gloves should be worn under the gloves for protection against leaks. Neoprene and butyl gloves are known to protect against hydrofluoric acid, however it is important to consult the manufacturer’s glove selection guide when selecting a glove for HF.

Examples of gloves for use with 48% HF: Best® Viton® and ChemMaster®; Ansell Sol-Vex®, Neoprene™, Orange Heavyweight and Chemi-Pro®; MAPA Trionic® E-194, Stanzoil® NK-22 and Stanzoil® NK-34

Examples of gloves for use with 60% HF: Ansell Neoprene™

If you have any questions about which protective clothing or gloves to purchase, contact EHS.

Eyewash/Emergency Shower

A combination eyewash/shower is required within 10 seconds (approximately 55 feet or 16.8 meters) away and must be accessible (unobstructed). The eyewash must be tested weekly.

Safe Work Practices

It is highly recommended never to work alone when using HF. Eating and drinking are not permitted in any laboratory at McGill. Always wash hands thoroughly after handling HF.

Treatment of HF Exposure

Calcium gluconate gel is a topical antidote for HF skin exposure and must be on-hand when working with HF. It works by combining with HF to form insoluble calcium fluoride, thus preventing the extraction of calcium from tissues and bones. Calcium gluconate gel has a limited shelf life and must be replaced as it expires.

Spill, Storage and Waste Issues

Spills

  • HF spilled outside a chemical fume hood: Evacuate the area and close the doors. Post a sign to
  • prevent others from entering. Call McGill Security Services (3000 Downtown Campus or 7777 Macdonald Campus).
  • HF spilled inside a chemical fume hood: The spill can be cleaned up by laboratory staff if they have the correct equipment, understand the hazards, know how to clean up the spill safely and dispose of the waste properly. Lime, soda, sodium bicarbonate, or a spill absorbent specified for HF should be used to neutralize and clean up a spill. Add neutralizers slowly as the reaction can be vigorous. Organic spill kits that contain Floor-dri, kitty litter, or sand must not be used because HF can react with silica to produce silicon tetrafluoride, a toxic gas.

All HF and HF waste must be stored in properly labelled and chemically compatible containers (e.g., polyethylene or Teflon). Glass, metal, and ceramic containers are not compatible with HF. HF should never be stored with incompatible chemicals such as ammonia or other alkaline materials. Always place in a low traffic area on a low protected shelf or in a labelled cupboard.

Waste

  • Waste HF should be placed in a chemically compatible container with a sealed lid and clearly
  • labelled. Contact Hazardous Waste Management (514-398-5066 or www.mcgill.ca/hwm) if you have any questions and for disposal of HF waste.
  • Many chemicals containing fluorine, such as ammonium fluoride, sodium fluoride, sulphur tetrafluoride, and ammonium bi-fluoride, may react with acid or water to produce HF. Review the MSDS of all fluoride compounds carefully for safety precautions to reduce the risk of creating a HF hazard.

Emergency Procedures for HF Exposures

All exposure to or contact with HF must receive immediate first aid and subsequent medical evaluation, even if the injury appears minor and no pain is felt. Speed is of the essence - HF can produce delayed effects and serious tissue damage without necessarily producing pain.

WARNING: HF EXPOSURE REQUIRES IMMEDIATE AND SPECIALIZED FIRST AID AND MEDICAL TREATMENT. IF UNTREATED OR IF IMPROPERLY TREATED, PERMANENT DAMAGE, DISABILITY OR DEATH MAY RESULT. CALCIUM GLUCONATE GEL MUST BE AVAILABLE IF HF IS BEING HANDLED.

Skin contact

  1. Immediately proceed to the nearest eyewash/shower and rinse the affected area thoroughly with water for a minimum of 5 minutes. Remove all contaminated clothing while continuing to flush with water. Speed and thoroughness is of primary importance.
  2. While the victim is rinsing the affected area, someone should call 911 for emergency medical assistance. At Macdonald campus, call McGill Security Services (7777).
  3. Immediately after thorough washing, start massaging calcium gluconate gel into the affected area. The person administering the gel should wear nitrile gloves to prevent a possible secondary HF burn. Apply gel frequently and massage continuously until pain and/or redness disappears or until medical care is given.
  4. During transportation to a medical facility, it is extremely important to continue massaging the calcium gluconate gel.

Eye contact

  1. Immediately proceed to the nearest eyewash station and flush eye for a minimum of 15 minutes with large amounts of gently flowing water. Hold eyelids open and away from the eye during irrigation to allow for thorough flushing.
  2. While the victim is rinsing their eyes, have someone call 911 for emergency medical assistance. At Macdonald campus, call McGill Security Services (7777).
  3. Continue to rinse affected area until emergency medical assistance arrives.
  4. Do not apply calcium gluconate gel to eyes!

Inhalation

Vapour exposures can cause skin & mucous membrane burns as well as damage pulmonary tissue.

  1. Immediately move the victim to fresh air and obtain medical attention.
  2. Call 911 for emergency medical assistance. At Macdonald campus, call McGill Security Services (7777)
  3. Obtain immediate medical attention.

In all cases of accidental exposure, you must bring a copy of the Material Safety Data Sheet; the

emergency room physician may be unaware of the treatment measures for HF. All accidents must be report to your supervisor and to Environmental Health & Safety via the Accident, Incident, and Occupational Disease Report Form available on the EHS website at http://www.mcgill.ca/ehs/forms/forms/accident-and-incident-report


References:

University of Pittsburgh, Guidelines for the Safe Use of Hydrofluoric Acid, Sept. 2004 Recommended Medical treatment for hydrofluoric acid Exposure. Honeywell Chemicals.