mfety in the
edited by MALCOLM M. RENFREW University of Idaho MOSCOW, Idaho 83843
Blaine C. McKusick Wilmington, DE
Before lahoratory waste can he disposed of, it must he classified to ensure that the disposal is done safely and in accordance with the regulations of the Environmental Protection Agency (EPA) and other state and federal agencies. Classificationis generally astrsightfarward process to the chemist who has generated the waste. However, an unlaheled bottle of unknown origin presents a problem. It cannot he allowed to sit around indefinitely, yet shippers and disposers will not accept it until it has been classified according to regulations. Classifying it may at first seem a daunting task to s chemist. However, although it is certainly more demanding to classify an unknown waste than one of known history, it neednot be difficult. Indeed, it is merely a special case of a nroblem most chemists have had experience with, the identification of an "unknown". Before getting into the details of dassifying an unknown waste, it will be helpful to discuss the closely related but simpler prohlem of classifying normal laboratory waste. It is necessary to know if a lahoratory waste has any of the characteristics of an EPA hazardous waste. The chemists and other technically trained people who generated
Mabe McKuskk received a BS in chemlcal engineering from the University of Minnesota in 1940 and a PhD in organic chew ism from the University of Illinois in 1944. He was with the Du Pont Company from 1945 until his retirement in 1982. Among his posts there were Associate Director of the Central Research Depamnem. Direnor of Me Labaatory for Agricunural Chemicab Research. and Assistant Director of the Haskell Labwatwy for Toxicology and Industrial Medicine. He helped prepare the National Research Council repml on disposal of chemicals from laboratories referred to in this article.
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: a r e the ones best qualified to make the initial classification heeause they know what chemicals they started with in their operations, what sorts of materials are likely to end up in the wastes, and what the general properties of the waste are. Put another way, from the history of the waste, the people who generated it generally know whether it has the characteristics of an EPA hazardous waste through being highly reactive toair or water, or a powerful oxidizing agent, or highly corrosive or ignitable, or because it contains an inorganic cyanide or sulfide. Although they may know little or nothinc about its toxicity heeause the main components have been little studied, they can sometimes make a good guess by analogy to closely related substances whose toxic properties are known. In case of doubt about toxicity, a waste should be considered toaic. Laboratory workers can characterize and label their wastes by such terms as "hydrocarbon mixture", "waste acetone", flammable laboratory solvents", "chlorobenzene still bottoms", solid oxidizer", and "aqueous cyanide mixture". Such characterizations enable the wastes to he directed to proper disposal. These descriptive terms may not he the exact ones required for shipping purposes, hut they enable someone versed in Department of Transportation (DOT) regulations to prepare proper shipping papers. With that as a background, let us consider unknown wastes. With a waste of unknown origin and composition, the goal is to determine its properties sufficiently that it can he classified in the same ways that ordinary laboratory waste is. We have all been plagued by unlaheled containers of ehemicals in our laboratories. Sometimes we have only ourselves to hlame-we were sloppy and did not label a container because we thought we would always remember what was in it. More often someone else is to blame, someone who left the lahoratory without cleaning up his or her area. Sometimes the original user is blameless, the fault lying with subsequent occupants of a lahoratory who have not been good housekeep-
ers, so that a well-labeled bottle of a valuable chemical has lost its label after 20 years. The solution to the problem is nothing new. The solution is about as old as chemistry, and it is called qualitative analysis. Most chemists have had training in qualitative inorganic analysis in school, and many have been trained in qualitative organic analysis as well. Some who have never had formal courses in qualitative analysis may have had the equivalent or better through yeam of lahoratory experience. However, even those who have had the courses and the lab experience can usually profit by a quick renew of relevant texts before examining those dingy old unlabeled bottles. The most relevant text for organic qualitative analysis is Shiner and Fuson, "Systematic Identification of Organic Compounds."' Sonun's "Introduction to SemimicroQualitative Ana l ~ s i s "has ~ lots of lore for identifying inorganic~.These hooks describe systematic, efficient ways to learn the identity of chemicals. Although it may take hours or days to establish the precise structure of a compound or the complete composition of a mixture, we do not need anywhere near that degree of precisionin classifyingasubstance for disposal as chemical waste. Our goal is to put it into one of the classifications that suffice for the wastes of known arigin that we are constantly generating in the laboratory. To establish the general class of waste that a substance belongs to can often he done quite quickly, sometimes in minutes. The successful practitioner of the art of identifying unknowns has same of the characteristics of Sherlock Halmes, himself a chemist, and according to Dr. Watson, an outstanding one. The mast admirable characteristicsof Mr. Holmes were his keenpowe n of observation and logical deduction. It also helps to have some characteristics of Casper Milquetoast, for same chemicals,
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Put about 0.1 g or two drops of the unknown on a watch elass. Does it smoke or rgnrte in air? If so, you have gone as far as you need tu with that substance. I.abel it 'Air Reactive". It cmld be a trialkylaluminum, a metal hydride, or potassium, among other things. Add 0.1 g t o 3 mL of water in a test tube. Is there a flame or a violent reaction? If so, it is "Water Reactive" by EPA definition and should be so labeled for disposal purposes. Acetyl chloride, phosphorus oxyehloride, lithium aluminum hydride, sodium, and sodium amide are examples of substances with this behavior. Fortunately, relatively few chemicals are air- or water-reactive. The main question to he answered by the simple test of adding 0.1 g of unknown to water is whether the suhstanee is soluble in water, and the answer tells a lot about the substance. Thus if w organic wrnpuund rs ,oluble, it probably contains m e or more functional groups such as hydroxyl, earboxyl, or amino, and probably has no more than five or six carbon atoms. If it is inorganic, it may well be a salt with an alkali metal as the cation, or a salt with nitrate, halide, or sulfate as the anion. If the substance dissolves, teat the rolutionwithpH paper. IfitspH isahove 1 2 . 5 ~ below 2, it fiw the EPA definition ofa corrosive suhstance and should he labeled for disposal with a descriptive phrase such as "CorrosiveLiquid Acid, pH 2"or "Corrosive Solid Base, pH 13". Because of the potential hazard of some oxidizing agents, especially the adventitious peroxides that may form in some organic compounds on exposure to air, it is wise to test for oxidizing power early. If the suhstance has heen found to he water soluble. adjust the pH of itssolution t o a little below 7 unless it raalreadv acidic and add a d r o ~ o f the solution to a milliliter of fresh lWo aqueous potassium iodide. A yellow or brown iodine color indicates an oxidizing agent such as an inorganic hypochlorite, ehlarate, persulfate, peroxide, or permanganate, or an organic peroxide or hydroperoxide. If an organic chemical is insoluble in water, it is ~
like some people, become disagreeable in their old age. Thus one should never forget that several large classes of compounds can form explosive peroxides on Long exposure to air. Examples are ethers with adjacent aliphatic C-H and olefins with allylic bydrogen. Hence one should work behind a shield until certain of not dealing with such a substance. Also, unless there is good reason ta believe that a hottle with a frozen glass stopper does not contain an explosive substance, one should not use heroic methods to get it open; it may have to be disposed of as a potential explosive. What is the first thing Mr. Holmes would do with an unknown? You can be sure he would not start by taking a sample. Instead he would examine the bottle for clues. Sometimes a manufacturer's name etched on a bottle limits the possibilities. The very size of a battle may tell something; a liter bottle probably does not contain a substance costing $ZO/gram; more likely it is some common chemical. A sealed ampoule probably contains a substance that is Low boiling or readily oxidized by air. Is the former owner of the hottle known? If so, knowing his field of chemistry can provide valuable clues. Next examine the contents of the hottle from the outside (item 1of the table). Is the substance a solid or a liquid? If a liquid, is it viscous or mobile? What color is it? Is it homogeneous? Tarry? Cautiously sniff the bottle cap for a characteristic odor; does it smell ammoniaeal? Vinegary? Perfumelike? Like rotten eggs? Sometimes the contents can be identified solely by such an inspection, perhaps followed by a simple confirmatory test. For example, many experienced cbemiPts can identify a hottle of waste sodium at a glance.
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tested for the presence of peroxides or hydroperoxides by adding 0.1 g to a milliliter of a 10%solution of potassium iodide in acetic acid. A positive potassium iodide test leads to a chemical being labeled something like "Solid Oxidizer" or "Organic Peroxide Oxidizer". Next is the ignition test, long used by chemists a t an early stage in the characterization of an unknown substance. A tenth of a gram of the suhstance is placed in a small porcelain crucible cover or a metal spoon. Bring a flame near and watch whether the suhstance hums, and if so, how readily and with what appearance (for example, a sooty yellow flame suggests a compound with an aromatic ring). Heat it gently, then strongly; this gives an indication of volatility. If the substance is a solid, does it melt or decompose? Is there a residue? If so, it is probably an inorganic salt or oxide; add a drop of water to see whether the residue dissolves and, if so, whether the solution is acidic or basic to pH paper. If the substance is flammable, it should he labeled "Flammable Solid" ar "Flammable Liquid" and is then ready to be sent on for dis~osal. I have described several simple tests--visual examination, exposure to air, exposure to water, test for solubility in water, ignition-which altogether require only a few minutes. From them the investigator may well have heen able to classify the unknown suffiuientlvfor laheline and diaoosal. . . and.. if not, has n&tbeless &ned auite a hit of kniwledee about the s;bstance; Amonnoth~-~~ ~~" er things, the inveatignto: probably knowa if it is organic or inorganic. The steps in further classification depend on which it is For an organic suhstance, the next step is to learn more about its solubility characteristics, as these are quickly determined and, as discussed in Shriner and Fuson's hook,' are often very revealing. Test its solubility in ether and, as appropriate, in 5% aqueous sodium hydroxide, 5% aqueous sodium bicarbonate, 5% hydrochloric acid, and eoncentrated sulfuric acid. Aa an example of bow the solubility testing works, consider a substance insoluble in water hut soluble in
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Outllne of a Method to Claaslfv Mod Unlabeled Laboratow Wastesa 1) Examine. 2) Expose to air. 3) Exposure to water.
If ignles or smokes, "Air Reactive".
4) KI test.
If insoluble: denser than water? If p ~ ~ i t i"Solid ~ e . Oxidizer" w "Organic Peroxide Oxidizer". If flammable. "Flammable Solid (aLiquid)".
Appearance? Stale? Color? Wor? If violem reactton, "Water Reactive". If noticeabiy soluble. pHpaper test: pH 12.5. "Conosive Base".
5) ignition test. 0) If organic:
7 ) If
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Journal of Chemical Education
volatile? Melts? Changes Color? Decomposes? A residue? If SO. soluble in water? If soluble, pH ot solution? a) Soluble In ether? bj If insoluble In water: soluble in 5% NaOH and 5% NaHCO.? "Oromlo Acid" " CI If naoluble in aqueous rsapents: solubllhy in conc. H,SO,? See ten. dl Copper wire test if posltwe. "Organic Haldes". consider other classlflcatlantests.InIrared analysis. NMR analysis el It not Clas~ified: a) Prussian blue test. if positive. "Solid (or Aqueous)Cyanide Mixture". b) Lead acetate test. If positive. "Metal Sulfide Midure". C) metal test. If posnive, "Heavy Metal Compounds". d) Mwe needed on what metals present? Consider atomic absorption analysis.
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ether and sodium hydroxide; it is probably a earhaxylic acid or phenol of moderate or high molecular weigh%an acid can he distinguished from a phenol by the solubility of the former in 5%sodium hicarbonate. Insolubility in water, sodium hydroxide, and hydrochloric acid. hut soluhilitv in ether and sulfuric acid. would suggest an ether, alcoh d , or ketone uf moderate or h i ~ molecular h weight or an olefin, an acetylene, or aneasily sulfonated aromatic hydrocarbon such as trimethylbenzene. If a substance is insoluble in any solvent tested, note whether it floats or sinks, as this gives an idea of its density that may he useful. For example, a substance denser than water may contain haloeen atoms. N&I prckup a little uf the substance i n s small loop of copper wire and hold it in s flame. Halogenated compounds impart a distinct green color to the flame. With this additional information in hand, many substances can probably now he classified and labeled in such ways as "Solid Organic Acid", "Flammable Water-soluhle Organic Liquid", and "Nonflammable Halogenated Organic Liquid". Should more information be needed, the next step might be a simple infrared scan, which will indicate functional groups a n d whether the suhstance is a single entity or a complex mixture. Additional testing can involve some of the simpler "classification tests" of S h i n e r and Fuson, such as testing for oxidizability with dilute aqueous potassium permanganate (which picks up easily oxidizable compounds like olefins and aldehydes), or for loosely hound halogen with alcoholic silver nitrate. A nuclear magnetic resonance (NMR) spectrum can often settle classifiestions that are still doubtful after having zone throueh all the above. If the ruhatance 1s inorganic, it is important tu see rf it contam cyanide or sulfide, for substances capable of generating hydrogen cyanide or hydrogen sulfide on exposure to acid are among EPA's classes of hazardous wastes. The most dangerous forms of cyanides and sulfides are the water-soluble salts. T o see if an aqueous inorganic solution or a water-soluble solid contains evanide. do the Pruxsian hlue tent; make a small sample of aqueoua d u t r o n strongly alkalme, add a few dn,psof ferroussulfalpaolut~on,boll the suspension of iron hydroxide 30 seconds, add 30% sulfuric acid dropwise until the iron hydroxide just dissolves, and see if a suspension of Prussian blue (ferric ferrocysnide) remains. To test a water-insoluble solid for cyanide, heat a little in 5 N hydrochloric acid with air bubbling first through the mixture and then through dilute sodium hydroxide to absorb entrained hydrogen cyanide; the Prussian hlue test is applied to the sodium hydroxide solution. If a test for cyanide is positive, label the substance "Solid Cyanide Mixture" or "Aqueous Cyanide Mixture" as the case may he. T o test an inorganic substance for sulfide, acidify a small sample of an aqueous solution or suspend a water-insoluble solid in 5 N hydrochloric acid, heat it, and see if the vapors turn moist lead acetate paper black by formation of lead sulfide. If so, label the substance "Solid Metal Mixture" or "Aqueous Metal Sulfide Mixture". Because some heavy metals are toxic, there is concern that they he disposed of properly. Almost all of them form insoluble
sulfides, so it is easy to establish their presence. If an inorganic suhstance is partly or wholly soluble in water or hot 5 N hydrochloric acid, neutralize a sample of the solution, add a little sodium sulfide solution, and again adjust the pH to neutral. I t is important to be close to pH 7, as some sulfides dissolve a t low pH, and some with excess sulfide present dissolve at high pH. A precipitate, usually dark colored, indicates the presence of heavy metal ions. The unknown would then be labeled "Solid Heavy Metal Mixture" or "Aaueous H e a w Metal Solution". This usually suffices, hut if it seems important to know exactly what metallic elements are present in a mixture, analysis by atomic ahsurption is useful. I n ronuluuion, the results of the teats described above and outlined in the tahle will generally provide sufficient information about an unknown substance for assignment of its hazard class. which in turn will lead to selection of a safe method of diaposal. Most chemi.its know how tudu these tests or can quickly learn. In mwt casesit rhould not take long, perhaps only minutes, to make a proper classification of a substance. With wastes for which these tests are inadequate, supplementary tests and some chemical shrewdness will often give a satisfactory answer.
88686 on a talk at the "Symposium on HarardWaste Management" at me National Meeting of the American Chemical Society In Chicago Sept. 10, 1985. and on the Natlanal Research Council Report, "Prudent Practices tor Disposal of Chemicals from Labwatwles", xii 282 pp.. $16.50, National Academy Press. 2101 Constitution Ave.. NW. Washington. DC 20418. 1983: pp 96-98. Shrber. R. L.: FuM~.R. C.: Cutin. D. Y.: and Morrlll. T. C. "Ttm Systematl~Identificationof Organic Compwnds". 6lh ed.; Wiley: New Ywk. 1980. Sorum. C. H. "lnboduction to Semimino Qualitative Analysis": PrenticeHall. Englewwd Cliffs, NJ. 1960; pp 175-208. Ow
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Volume 63
Number 5 May 1986
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