Storage of Chemicals in Laboratories

Index

  1. Introduction
  2. Basic Legal Requirements
  3. Storage Facilities and Practices
    1. Solvents and other flammables
    2. Peroxidizable substances
    3. Oxidizing Agents
    4. Reducing agents
    5. Acids and Bases
    6. Health Hazards
    7. Nonhazardous materials
  4. Compressed Gases
  5. Summary of Storage Recommendations
  6. Labels
  7. Containers
  8. Maintenance

A. Introduction.

Two major groups of regulations issued by Federal and State agencies affect the disposal and storage of chemicals by academic laboratories. OSHA, in both Federal and State incarnations, propounds regulations intended to ensure worker safety in laboratories. The US EPA and Maine DEP regulate laboratory practices that have the potential for harm to the environment. These two sets of agencies, with two different purposes, sometimes produce regulations that seem to conflict. However, both sets of rules specify the conditions under which chemicals can be kept, the information that must be available to users of the chemicals, and what chemicals can be disposed of in what ways.

Without spelling out the rules in detail, we will try here to provide some general information about what one can and can't do, including good practice for the storage of chemicals. The information here is directed specifically to chemistry programs, and does not include janitorial, secretarial, and other areas.

B. Basic Legal Requirements.

  1. The Department of Labor (OSHA), requires you to have a Material Safety Data Sheet (MSDS) for every substance you keep or use in a laboratory. The MSDS provides information on any known toxic properties of the substance, its corrosiveness or flammability, and how to deal with spills, accidental exposure, and fires involving the substance. The MSDS is the key to safe laboratory practice.

  2. The law does not care how or where you get the MSDS, just that you have it immediately available in the laboratory. If an MSDS was not provided with a chemical purchased for use in your lab, the easiest way to get one is to use the Internet. A collection of Web links to MSDS is available on the Department Web page: http://chemistry.umeche.maine.edu/Safety.html. Although Maine OSHA formerly allowed rapid Internet access to MSDS to substitute for hard copies, they now require the hard copies to be available at all times. The Department Safety Committee recommends a set of notebooks containing alphabetized MSDS. MSDS in a pile on a desk are useless, since you cannot rapidly find the one needed.

  3. The law also provides that any employee who works with these chemicals be trained specifically in the safe handling of each chemical. The training can be very basic, such as a discussion of general safe laboratory practice, and the specific safety procedures indicated in the MSDS. Training must be provided for new employees as part of their entrance procedure, and must be repeated annually. A description of the plan for providing this training must be put in writing. This handbook, and others the Committee will provide on other subjects, will become part of notebooks kept in each laboratory to record the training, and to serve as a memory aid.

C. Storage Facilities and Practices.

Modern safe practice and OSHA regulations require the storage of like classes of compounds together, away from other compounds with which they might react if their containers leaked or were broken. Color coding of containers for various storage classes is now common practice among chemical manufacturers. The scheme is described below, and on the posters in each of our laboratories. Consider the following classes:

  1. Solvents and other flammables. There are two major aspects of safe practice in the storage of solvents: (a) limit the quantity to be stored, and (b) use proper storage equipment.

    We all have the habit of buying large quantities of goods and storing the excess until it is needed. With chemicals, this practice is deceptively cost-saving. The cost of storage and potential disposal must be factored in. Therefore, BUY THE SMALLEST QUANTITY OF SOLVENT THAT WILL SERVE THE PURPOSE! This is a good rule for any chemical purchase, not just flammables.

    The proper equipment for storing solvents includes metal safety cans for quantities larger than one gallon, or double-walled metal cabinets approved by the National Fire Prevention Association, in which the solvent containers should be kept when not in use. (Such cabinets are available from all major laboratory supply and laboratory furniture houses.) Local fire code requires that vents in the cabinets should be connected into a fume hood that runs continuously, or into a ventilation system designed specifically for the purpose, or should be kept plugged.

    Common solvents that require this treatment include: methyl, ethyl, and isopropyl alcohols; acetone and methyl ethyl ketone; methyl, ethyl, and butyl acetates; all ethers; pentane, hexane, heptane, octane, and "light petroleum" or "petroleum ether"; benzene, toluene, and xylene; and carbon disulfide. The last substance has a flash point of 30 degrees below zero Celsius, and its use in teaching laboratories is strongly discouraged. Likewise the use of the chlorinated solvents carbon tetrachloride, chloroform, and methylene chloride (dichloromethane) is discouraged because of their toxicity.

  2. Peroxidizable substances. Particular attention must be given to substances that form explosive peroxides on prolonged contact with air. All chemicals should be dated when they arrive at the laboratory or stockroom (a Chart outlining a standard arrival procedure for new chemicals is available for posting in laboratories); this is especially critical for peroxidizables.

    1. The following are especially hazardous and should be disposed of after three months:

      isopropyl ether divinyl acetylene
      vinylidene chloride potassium metal
      sodium amide  

      These materials should be distinguished by placing a red band or dot on the label.

    2. The following should be discarded after six months:

      diethyl ether tetrahydrofuran
      dioxane diacetylene
      methyl acetylene cumene
      methyl isobutyl ketone ethylene glycol dimethyl ether (glyme)
      tetralin cyclohexene, cyclopentene
      methylcycloalkanes  

      These materials also are distinguished by a red band or dot on the label.

      Since most peroxidizable materials are solvents and are flammable, they must be kept in a flammables cabinet; a separate one for peroxidizables as opposed to merely flammables is a good idea, but separation by shelf is acceptable.

  3. Oxidizing Agents should be stored away from substances that they may oxidize vigorously. Oxidants include: perchloric acid and perchlorate salts; chlorate salts, hypochlorites such as bleaching powders and "liquid bleach"; liquid bromine; perbromate and bromate salts; chromic acid and its salts; hydrogen peroxide; and potassium permanganate. Concentrated nitric and sulfuric acids also are oxidants; they must be stored together, and away from all other substances. A fire has occurred in Aubert Hall when bottles of nitric and formic acids, carelessly stored together, leaked.

    Oxidizing agents are color coded yellow.

    NOTE: perchloric acid may be used only in a specially designed hood, intended to prevent its coming in contact with oxidizable organics or metals with which it forms explosive salts. We have no such hoods in Aubert Hall. Hence, perchloric acid may not be used without explicit permission from the Department Chair.

  4. Reducing agents are substances that are especially easily oxidized. Particular care should be taken to keep them separate from oxidizing agents, both in storage and when placed out in the laboratory for student use. The accidental combining of oxidizing and reducing agents by confused students represents a significant fire and explosion hazard. Such materials include: elemental sulfur in any allotropic form; powdered carbon (carbon black, activated carbon, powdered charcoal, graphite powder); sodium and potassium metals; most aldehydes; and all hydrocarbons and most solvents. Paper, sawdust, and wood shavings also are reducing agents.

  5. Acids and Bases are of concern for two reasons: they are generally corrosive, and their reactions with each other are usually highly exothermic. Hence acids and bases must be stored apart from each other.

    (Multiple problems: incompatibles stored together, no secondary containment)

    Acids commonly encountered in the chemistry laboratory include: hydrochloric, nitric, sulfuric, and acetic acids. Hydrofluoric acid is so corrosive, and produces such vicious burns, that its use is not recommended in any teaching laboratory. Storage problems are minimized if acids are purchased in the smallest practicable containers, rather than in the common 1-gal jugs.

    The most common bases are ammonium hydroxide (aqueous ammonia), sodium and potassium hydroxides (typically in pellet form), calcium hydroxide (slaked lime), and sodium carbonate (washing soda). A familiar sight in many stockrooms where acids and bases are not segregated is the white crust of ammonium salts formed by fumes from ammonium hydroxide combining with acid fumes. This crust is mildly acidic, and over time can degrade labels and both wood and metal storage shelves.

    Acids and bases, and other corrosive materials, should be distinguished by a white dot or band on the label.

  6. Health Hazards are substances that pose a health hazard through either acute (immediate) or chronic (long-term) toxicity. Examples of substances that are acutely toxic are sodium cyanide and ammonium molybdate; chronic toxicity is displayed by many organics such as aniline derivatives, chlorinated hydrocarbons, and thiocyanates. Check the MSDS if you are not sure whether a substance belongs in this category.

    These substances should be stored together, away from materials of other classes. Labels should be marked with a blue dot or band.

  7. Nonhazardous materials are those known to pose no health risks. Examples are simple salts such as calcium chloride, buffer solutions, indicators, copper metal, and so on. The materials can be kept in a general chemical storage area. Their labels should bear green or gray dots or bands.

What all of this boils down to is that a laboratory needs five chemical storage areas:

  1. Sulfuric and nitric acids; perchloric acid would be kept with these, but since we have no perchloric acid hoods in Aubert, no one should have perchloric acid. Chromic acid solutions also belong here.

  2. Other corrosive acids, such as hydrochloric, acetic, and formic.

  3. Corrosive bases: ammonium hydroxide, sodium hydroxide, potassium hydroxide

  4. Flammables, in an approved cabinet.

  5. General storage, permitting separation of the various hazard categories on separate shelves

Finally, note that all liquids, in quantities greater than 250 mL, require secondary containment. That is, they must be placed inside a chemically resistant tub large enough to contain the contents should the bottle break. Polypropylene or polyethylene tubs can be obtained from most lab supply houses; the simple polystyrene tubs available in supermarkets are acceptable for all except corrosive liquids. Multiple containers may be kept in a single tub, provided they are of the same hazard category. The tub must be large enough to contain the total amount of liquid in all of the containers. (Approved flammables cabinets have secondary containment built in.)

D. Compressed Gases.

Storage of compressed gases in the laboratory requires precautions unique to the unusual containers in which these materials are kept, and the high pressures to which they are subject.

  1. Full size cylinders

    • must be fastened to a laboratory bench or other stable, immovable object using a heavy canvas strap or a chain; the fastening should be placed about one-third of the way down from the top of the cylinder.

      (An accident waiting to happen)

    • must have either the appropriate type of pressure regulator or the protective cap screwed in place at all times.

    • Must be located away from sources of significant heat, such as radiators.

  2. Lecture bottles

    • must be placed in a rack designed for the purpose (resembling an oversize test-tube rack) or be firmly clamped to a ring stand with a heavy base, in an upright position.

    • may not be used or stored lying on their sides.

    These precautions are designed to avoid the cylinder cap being broken off through a fall or a sudden increase in pressure. In such events explosions may result, and the gas cylinder may become a dangerous projectile.

    E. Summary of Storage Recommendations

    Segregation of chemicals by class within appropriate cabinets is the key idea. One may not merely arrange substances on a shelf alphabetically without regard to their chemical characteristics. Solvents must have their own special fire-resistant cabinets; oxidants are stored away from reductants; acids are stored away from bases; and peroxidizables are monitored and discarded at regular intervals. A good idea is color coding the edges of the shelves to match the color coding for the category of substance stored there. Within, each category, materials can be arranged alphabetically. More details on the color coding scheme are available:

    It is strongly recommended that chemical storage within research and teaching laboratories be minimized. Again, buy the minimum practical quantity, use it promptly after purchase, and dispose of any excess.

    Rooms chosen for chemical storage should be well-ventilated and preferably equipped with an exhaust fan that will accomplish at least six air changes per hour.

    Significant quantities of chemicals should not be stored in a room that is regularly occupied by students or faculty who are not conducting experiments.

    Furthermore, consumption or storage of food or beverages of ANY kind is strictly forbidden in rooms where chemicals are stored or used!

    The best shelving is steel with acid-resistant paint; next best is wood with acid-resistant paint. Shelving should be labeled clearly to indicate what kinds of chemicals may be stored there. As noted above, an easy way to do this is to color-code the edges of shelves with paint or tape to match the color-coding of labels; materials then can be returned to proper storage at a glance.

    Storage areas must be equipped with fire extinguishers, eyewash fountains, and materials for cleaning up spills. Kitty litter is excellent for this latter purpose, being both adsorbent and inert. A five-gallon bucket of litter will absorb the contents of a standard 2 L reagent bottle. Surround the spill with litter to contain it, and then cover it completely. Sweep it up with implements kept specifically for that purpose. Contaminated litter then is placed into a heavy plastic bag, and arrangements made for its pickup by EH&S, as described below.

    Fume hoods normally should not be used for storage of chemicals. When such storage cannot be avoided, because properly ventilated cabinets are not available, or because the compounds are particularly odiferous (e.g., thiols), the bottles must be placed in a plastic tub or tray to contain any leakage or spill. Hoods being used for storage may not be used for experimentation, and should be labeled clearly as storage hoods.

    F. Labels.

    Labels on commercially available chemicals now must conform with both federal and state law. These laws mandate the appearance of the name of the substance and any common synonyms, as well as information on the toxicity and other hazards associated with the substance. Labels of most purchased chemicals carry the colorations noted above.

    1. Additional Information. For your own benefit, and that of anyone else who may use the chemical storage area in future, you should add to all labels the date on which the material was acquired and the storage location.

      Adding the date will allow easy culling of overage substances. Furthermore, as manufacturing and purification processes generally improve with time, the date of purchase is an indication of quality.

      Storage location should indicate storage room, the cabinet or set of shelves, and the individual shelf. Thus, a label might bear the notation: 223-C-5, meaning room 223, cabinet C, shelf 5.

    2. Label Materials. The best way to add additional information is with a small label of your own, stuck over a corner of the manufacturers' label, or just above it.

      If the original label has disintegrated or otherwise been lost, you should make a new one, containing as much of the necessary information as possible. Use good quality paper or polyethylene labels and India ink.

      Labels, both your own and the manufacturers', should be protected against spills and fading. Lab supply houses sell label lacquers that are chemical-resistant; an easy-to-use option is a clear polyester tape that is water-resistant and also will stand up to casual exposure to acids, bases, and organic solvents. It is available from Aldrich Chemical Company in 36-yd rolls ranging in price from $7 to $15, depending on width. The Department provides adhesive dots for color coding chemicals acquired prior to the introduction of such coding by manufacturers.

    3. All chemicals, whether commercial materials or samples prepared in the laboratory, must be labeled. Absence of identification is a violation of the law.

      G. Containers

      Except for flammable solvents, which should be transferred to safety cans if proper cabinets are unavailable, the containers, usually of glass, in which chemicals are received from the supply house are appropriate for storage for reasonable periods of time. Materials received in sealed glass ampoules should be used completely or the excess should be disposed of. Only a professional should attempt to reseal an ampoule.

      In the past, however, chemicals often were received in inappropriate containers or were transferred locally into inappropriate containers. The best method of dealing with these materials is to dispose of them, especially if the cap is corroded. If you must keep the material, transfer it carefully to a new container purchased for the purpose from a lab supply house. Label it clearly, including the information that it has been repackaged and both the date of acquisition (if known) and the date of repackaging. Supply houses also sell Teflon cap liners, which can be used to protect older containers not yet deteriorated.

      The law requires that damaged containers be disposed of immediately. "Damaged" includes: cracked or broken caps; chipped threads on bottle necks; and corrosion of metal containers, even if an interior glass container is intact.

      H. Maintenance.

      At monthly intervals, inspect the storage area. Make sure that all chemicals are in their proper locations. Remove for disposal any substances with leaking containers, and repackage or dispose of any with caps that show signs of corrosion. Unless you are certain that you will use them in the near future, remove for disposal bottles with only small amounts of material remaining in them, and anything more than two years old.

      If you store volatiles that represent long-term health hazards, such as benzene and chlorinated solvents, regular air-sampling is a good idea. Lab supply houses sell sampling kits, the core of which is a cartridge that is exposed for a period of time and then mailed in for analysis. The price of the kit includes the analysis. If you find that you are unable to store such materials without exceeding safe limits, then perhaps you should rethink your need for them.

      If you believe that your laboratory exposes you to dangerous levels of these substances, you have the right

      • to ask the Department to arrange for testing of air quality;

      • to ask the Department to arrange to have you examined, at University expense, by a medical specialist in chemical exposure.

      J. Additional Information.

      More detailed information about the storage of chemicals may be found in the book, Safe Storage of Laboratory Chemicals, by D. A. Pipitone, John Wiley and Sons, New York, 1984, available from the publisher for $68 plus postage. Improving Safety in the Chemical Laboratory, by J. A. Young, also from Wiley ($45) is likewise helpful.


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