Dr Mike Casey

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Safe Handling of Hazardous Chemicals

• Dr Mike Casey
• UCD School of Chemistry Chemical Biology
• Safety Training Course, September 2007
• Basic Rules
• Hazard Assessments
• Common Classes of Hazardous Chemicals

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• Safety is of paramount importance in the
  laboratory.
• You have a moral and legal responsibility to work
  safely.
• Your supervisor is responsible for ensuring that
  you work safely.

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• 1. Basic Rules Avoiding Common Hazards
• Treat all chemicals with caution.
• Always wear safety spectacles and a lab coat.
• Do not get any compounds, especially those for
  which no specific safety information is
  available, on your hands or skin.
• Do not breathe vapours or dust.
• Use protective clothing, e.g. gloves, as
  necessary and only handle more dangerous or
  unpleasant compounds in fume cupboards.
• Wash your hands thoroughly immediately after
  leaving the lab.

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• Do not leave spillages.
• Clean up spillages promptly and safely.
• It is particularly important that you clean up
  spillages in communal work areas, e.g. beside
  balances or instruments.
• Dispose of hazardous material safely.
• Proper methods for disposal of waste solvents and
  chemicals must be used. Consult your supervisor
  and books on safe disposal procedures. Do not
  allow hazardous waste or spent reagents to
  accumulate, deal with them promptly.
• All sharps must be placed in the special bins
  provided.
• All laboratory waste must be segregated in the
  special bins provided.

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• What to do if chemicals get on your clothing or
  skin, or in your eyes.
• If a hazardous chemical gets on your clothing,
  remove the contaminated clothing and wash any
  area of skin that might have been affected with
  copious amounts of water. Continue washing for
  at least 5 minutes.
• If a hazardous chemical gets on your skin, seek
  help from colleagues or supervisors, and wash
  immediately with copious amounts of water.
  Continue washing for at least 5 minutes.
• If any chemical gets in your eyes, summon help
  and wash immediately with water. Try to wash
  under the eyelids, and continue washing until
  arrangements are made to take you to hospital for
  an eye check.

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• Be aware of the danger of fires.
• The consequences of a fire are potentially
  catastrophic.
• Many solvents are both volatile and flammable,
  and may ignite if the liquid or the vapour comes
  in contact with flames or hot surfaces.
• Diethyl ether and hydrocarbons, e.g. petroleum
  spirits, are particularly dangerous in this
  respect.
• Take great care with solvent stills. Make sure
  that they do not run dry, or overflow. Never
  leave them running unattended.
• Do not use a Bunsen or any other naked flame
  except in specifically designated areas.
• If the fire alarm sounds, quickly secure any
  potentially dangerous apparatus or chemicals, and
  leave via the nearest fire exit. Obey all
  instructions from the fire marshals.

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• What to do if there is a fire.
• If there is a very small fire, consider if it can
  be extinguished by cutting off the oxygen supply,
  e.g. by placing a clock glass over a vessel
  containing a burning chemical.
• If the fire is larger, or you are in any doubt,
  summon help and leave the area.
• If the fire is small and you have been trained in
  the use of fire extinguishers, try to use the
  appropriate extinguisher. Otherwise leave the
  area, and if necessary, set off the fire alarm.
• If the fire alarm sounds, leave the building
  immediately via the nearest emergency exit. Obey
  all instructions from fire marshals.

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• Do not work alone.
• It is a strict rule that you never do
  experimental work unless there is another person
  close by.
• If you are working out of hours, you must sign
  the register beside the main entrance.
• Obey the rules regarding unattended experiments.
• Unattended experiments are potentially very
  dangerous, strict adherence to the Departmental
  guidelines is required.
• Only use thermostatted heating baths.
• Fit water switches to reflux apparatus, so that
  the power will be cut off if the water pressure
  drops.
• Secure water tubing to taps and apparatus
  securely using plastic ties.

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2. Hazard Assessments The School Safety
Instructions, and the law, require that you check
the hazards of, and safe handling procedures for,
all chemicals and procedures that you may
encounter before you carry out experimental work.
This requirement is implemented by means of
hazard assessments.

• There is a strict requirement that you carry out
  a "hazard assessment" before starting each new
  experiment.
• The safety audit consists of
• A thorough assessment of the potential hazards
  arising from the use of chemicals and apparatus.
  Consult "Material Safety Data Sheets" (MSDS) and
  related sources to obtain information on hazards.
  
• A listing of the control measures to be adopted
  to minimise the risk of an accident.
• An assessment of the level of the risk involved.

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• Information on hazards and safe handling
  procedures
• The information you will need can be found in
  various books including "The Sigma Aldrich
  Catalogue of Safety Data", "Hazards in the
  Chemical Laboratory", and Prudent Practices in
  the Laboratory (also available online).
• A collection of International Chemical Safety
  Cards, which are very nicely presented summaries
  of essential safety data for compounds, is
  available at http//www.ilo.org/public/english/pr
  otection/safework/cis/products/icsc/dtasht/index.h
  tm.
• Extensive compilations of "Material Safety Data
  Sheets" (MSDS) are also available on the UCD
  computer servers and on the internet. A very
  useful site from which you can search for MSDSs
  is http//hazard.com/msds/.

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• Information on hazards.
• Brief "Safety and Risk Phrases" can be found for
  each compound in chemical suppliers catalogues.
  For example
• R12 is Extremely flammable.
• R23/24 is Toxic by inhalation and in contact
  with skin.
• S15 is Keep away from heat.
• S36/39 is Wear suitable protective clothing and
  eye/face protection.
• MSDSs tend to contain exhaustive listings of
  every possible hazard. It is sometimes difficult
  to pick out the hazards that you really need to
  be concerned about. The ICSCs and risk and
  safety phrases highlight the hazards more
  clearly.
• Watch out for phrases such as highly or
  extremely flammable, explosive, toxic or very
  toxic, severe, cancer, etc.

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• 3. Common Classes of Hazardous Substances
• Solvents Dont become complacent about commonly
  used solvents
• Several, including hydrocarbons, ethers, alcohol
  and acetone are highly flammable (see earlier).
  These are also incompatible with many oxidising
  agents.
• Chlorinated solvents may react explosively with
  alkali metals and react violently with alkyl
  metals. Chloroform (CHCl3) is sensitive to base
  and may react violently with acetone in the
  presence of base. Keep waste chlorinated
  solvents separate from non-chlorinated.
• Some, including benzene, carbontetrachloride,
  hexane and hexamethylphosphoric triamide (HMPA)
  are known carcinogens. Use them only if
  absolutely necessary, and work carefully in good
  fumehood.
• Acetonitrile (CH3CN) is toxic.
• Nitromethane, and other nitroalkanes can react
  violently with strong bases and with bromine.
• Dimethyl sulfoxide (DMSO) reacts very vigorously
  with acid chlorides and other reactive
  electrophiles.

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• Alkali metals
• Sodium is still widely used for drying solvents.
  It reacts violently with water with formation of
  the highly flammable hydrogen! Take great care
  in disposing of sodium residues. Quench by slow
  addition of isopropanol, caution H2 evolution,
  and then ethanol, before adding water.
• Never use sodium to dry chlorinated solvents a
  violent explosion may result.
• Potassium is much more reactive than sodium and
  requires extreme care.
• Metal hydrides
• Sodium hydride (NaH) and potassium hydride (KH)
  are finely divided powders which are used as
  powerful bases. They react violently with water
  with formation of the highly flammable hydrogen
  gas, and ignite on contact with moist air. They
  are stored as suspension in mineral oil, which
  are relatively safe and can be exposed, briefly,
  to the air.
• Sodium and potassium amides (Na/KNH2) have
  similar reactivity.
• Lithium aluminium hydride reacts violently with
  water. Be careful in working up reactions. Use
  pellets rather than powder, if possible, because
  the powder can be blown around, dispersed by
  static, etc. Keep away from filter paper, other
  combustible materials.
• Diisobutylaluminium hydride (DIBAL), another
  useful reducing agent, is sold as solutions in
  hydrocarbon solvents. It is extremely reactive
  to air and moisture and must be handled using
  inert atmosphere techniques (see alkyllithiums
  below).

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• Alkyllithiums and other alkylmetals
• Available as solutions in hydrocarbon solvents
  and used as powerful bases and nucleophiles.
  React violently with water and air. Must be kept
  under an inert atmosphere and transferred using
  syringe techniques. Consult textbooks and more
  experienced colleagues for instruction on safe
  technique.
• Old bottles must be disposed of carefully and
  promptly, and not allowed to accumulate. Once
  you suspect that the solution has deteriorated,
  quench by slow addition to isopropanol.
• Tert-butyllithium is pyrophoric and needs special
  syringe techniques.
• Grignard reagents, alkylaluminium and alkylzinc
  compounds, and boranes have similar reactivity
  and must be handled using inert-atmosphere
  techniques.
• Many of these compounds also react violently with
  halogenated solvents.

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• Halogens
• Bromine is toxic and highly corrosive and it
  reacts violently with many easily oxidisable
  compounds.
• Iodine is harmful by inhalation and by contact
  with skin.
• Chlorine and fluorine are very reactive toxic
  gases that require use of special procedures.
• Strong Lewis acids
• Several metal halides and metalloid halides
  (AlCl3 , PCl3, PCl5, BCl3, BBr3, etc) react very
  vigorously with water. Handling details vary,
  but be careful with these strong Lewis acids.
• Acyl halides and related compounds
• Acid chlorides react vigorously with water and
  other nucleophiles with the formation of highly
  corrosive HCl. Many have pungent unpleasant
  odours. Keep them in well-sealed containers,
  preferably with an outer container as well.
• Oxalyl chloride is particularly reactive.
• Phosgene (ClCOCl) is a very toxic gas and should
  not be used unless absolutely necessary.
• Many inorganic acid halides (SOCl2, POCl3, etc)
  are similar to organic acid chlorides, as are
  various anhydrides such as phosphorus pentoxide
  (P2O5) and barium oxide (BaO).

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• Alkylating agents
• Strong alkylating agents are generally very
  toxic.
• Iodomethane is very volatile aand toxic. Be
  careful in working up reactions.
• Dimethyl sulfate (Me2SO4) is toxic, can cause
  severe burns and is aprobable human carcinogen.
• Methyl triflate (MeOSO2CF3) is a powerful
  alkylating agent and is very toxic.
• Many benzyl halides (ArCH2X) are potent
  lachrymators. Careful containment, cleaning and
  disposal needed.
• Sulfur compounds
• Thiols, volatile sulfides disulfides often have
  a terrible tench and some are toxic. Careful
  containment, scrubbing, cleaning and disposal
  needed. Advance notice must be given to John
  Coffey if they are to be used.
• Hydrogen sulfide (H2S) may be generated in
  reactions of some sulfur compounds. It is
  volatile, toxic, and extremely foul smelling, and
  requires the same precautions as above.

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• Oxidising agents
• Strong oxidising agents, e.g. mCPBA, tBuOOH,
  H2O2, O3, CH3CO3H, KMnO4, and R4NMnO4 are widely
  used . They may react violently with easily
  oxidised materials, such as alcohol, acetone and
  hydrocarbons, to cause fire or even explosion.
  Check carefully for chemical incompatibility
  before use ands keep them away from potential
  fuels.
• Perchloric acid (HClO4) is also a strong
  oxidising agent and nitric acid (HNO3)
  sufficiently oxidising to ignite ethanol and
  other solvents
• OsO4 is very toxic.
• Explosion hazards
• Hydrogen gas is extremely flammable and forms
  explosive mixtures with air.
• Azides (RN3) are prone to explosive
  decomposition. Extreme care is needed, and you
  should only work with small quantities, use
  shields, etc. Sodium azide (NaN3) is also toxic.
• Diazonium salts (ArN2X) are potentially explosive
  and should be kept cold and never be isolated
  from solution.
• Many perchlorate salts are highly explosive, and
  perchloric acid (HClO4) is very corrosive and
  strongly oxidising.
• Diazomethane (CH2N2) is prone to explosive
  decomposition. Extreme care is needed, working
  with small quantities only, and special glassware
  must be used.

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• Miscellaneous very hazardous substances
• Carbon monoxide Extremely toxic gas and is
  odourless so there is no warning.
• Cyanide salts, Hydrogen cyanide Extremely
  toxic. Special permission needed for use,
  special precautions must be in place. Consult
  John Coffey before use.
• Hydrofluoric acid (HF) Causes very severe burns.
  Special permission needed for use, special
  precautions must be in place. Consult John Coffey
  before use.
• Many compounds of Cr, As, Cd, Pb, Hg, and Be are
  very toxic.
• Heterogeneous hydrogenation catalysts
• Hydrogenation catalysts, particularly palladium
  on carbon (Pd/C), and Raney nickel, especially
  when they have hydrogen adsorbed on their surface
  are pyrophoric and will ignite easily combustible
  materials. They should be kept under an inert
  atmosphere and, if possible, kept wet. Dry
  catalyst should never be added to an organic
  solvent in the presence of air, and great care
  should be taken when working up hydrogenation
  reactions.

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• Conclusion Ignorance is the biggest danger
• Very hazardous substances can be handled with
  little risk, provided you
• are aware of the hazards,
• have found safe purification and handling
  procedures, and
• have found safe waste disposal procedures.
• The key is to get advice from your supervisor and
  from senior colleagues, and to consult
  authoritative reference sources.

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