Risk Level 5. "PROBABLE INJURY AND DESTRUCTION" Task must not be undertaken without close senior supervision, i.e. the Adviser must be present. Tasks in this level would never be assigned to Undergraduates. Procedure that requires special care, containment, location and/or facilities. Administrative procedures control is insufficient. Special PPE, Engineering and Isolation control is mandatory. Full risk assessment, detailed procedures, coordination and documentation are required. Work where an incident will very likely cause permanent disability. Significant damage to the laboratory and facilities would occur. Experienced Workers. |
All staff, students and employees who work in labs containing Perchloric Acid should familiarize themselves with this document. A sign off sheet should be kept that states the person has read this document and is aware of the unique dangers and special precautions that need to be taken when handling perchloric acid.
Perchloric acid (HClO4) is a colorless, odorless, fuming liquid that is miscible with water and extremely corrosive. Perchloric acid is noncombustible; however, the anhydrous (dehydrated) acid and certain perchlorate salts of organic, organometallic, and inorganic cations present a serious explosion hazard and have been set off by either heat or shock. Because of perchloric acid's extremely corrosive physical properties and its tendency to react violently with many oxidizable substances it is among the most hazardous substances found in the laboratory and should be used and stored with extreme care.
Perchloric acid is very corrosive to all living tissue. It can cause severe burns on contact with eyes, skin, and mucous membranes and is a severe irritant. Its acute toxicity is moderate. Perchloric acid has not been shown to be carcinogenic nor a reproductive or developmental toxin in humans.
Although perchloric acid is not combustible, the anhydrous form is a serious explosion hazard due to its unstable nature and ability to react violently with many organic materials (e.g., wood, paper, cotton etc.). Aqueous perchloric acid can cause violent explosions if it is misused, or if it is in concentrations greater than normal commercial grade strength (72%). At concentrations less than 72% aqueous perchloric acid will not decompose spontaneously nor explode on standing. Many heavy metal perchlorates and organic perchlorate salts are very sensitive explosives. Mixtures of perchlorates with many oxidizable compounds are explosive. When used cold, 70% perchloric acid acts as a strong acid but is not considered to be a strong oxidizing agent; however, when heated it acts as a strong oxidizing agent. More concentrated solutions are strong oxidizers and increases in temperature increase the oxidizing power of perchloric acid. Hot concentrated solutions are very, very dangerous and should not be taken lightly.
Perchlorates should not be used as drying agents if there is any possibility of contact with organic compounds or of proximity to a dehydrating acid strong enough to concentrate the perchloric acid (e.g., a drying train that has a bubble counter containing sulfuric acid). Safer drying agents should be used.
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Refer to the Chemical Hazard Assessment Guide to access various resources including MSDSs, other internet resources, and publications such as Prudent Practices in the Laboratory, etc. It is very important that all of the available information regarding the use of perchloric acid be thoroughly reviewed by all parties before any work begins. Determine the potential risks before beginning an experiment.
This material may cause a number of different problems. Therefore it is essential that users undergo training so as to understand all the risks and consequences. That training must be recorded in the specific procedures developed.
Use the information from the hazard assessment process to identify work practices, engineering controls, and protective equipment necessary to perform the experiment safely. This information should be included in written lab procedures or as separate safety Standard Operating Procedures (SOPs).
Storage of unused liquid inventories should be put in polyethylene secondary containers (large enough to contain the entire contents if the original container should rupture) and isolated from other oxidizable materials and dehydrating agents. Make sure perchloric acid is kept in clearly labeled, compatible containers and stored in compatible storage units (e.g., do not store in wooden cabinets nor on paper lined shelves, etc). Be sure to label all containers that contain perchloric acid, as well as all other hazardous waste in the laboratory!
Evaporations of perchloric acid in chemical fume hoods should never be done unless the chemical fume hood is a special perchloric acid fume hood. These special fume hoods are designed in such a way as to allow systematic wash downs with water after evaporations of perchloric acid. This will put the perchlorates back into solution and avoid inadvertent explosions due to shock or heat. Many documented accidents have occurred over the years surrounding the use of perchloric acid and subsequent explosions due to improper handling. Before attempting to perform any perchloric acid evaporations, contact the Chemical Safety Officer .
Specific procedures must be written for the tasks to be performed with Perchloric Acid. Refer to the Guidance Note
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Perchloric acid spills are serious and care should be taken to follow all chemical spill clean up procedures carefully. All personal protective equipment including the appropriate gloves, safety glasses, and lab coat or apron must be worn. Small or dilute concentrations (10 ml of >50% or 100 ml of dilute) can be cleaned up using a spill kit. The entire spill kit containing the clean up materials can then be labeled and placed in a satellite accumulation area for pickup and disposal. If large amounts or higher concentrations of acid are spilled, or if the spill is beyond your ability and training to clean up, evacuate the laboratory and contact the Tufts police from a safe location.
All laboratory personnel should be familiar with first aid procedures before working with perchloric acid.
Symptoms of overexposure include irritation and/or burning of the affected area. Inhalation burns are serious and require immediate medical attention. If perchloric acid is ingested, drink approximately 8 oz. of water and seek medical attention. Do not induce vomiting.