FEATURE

Management of time-sensitivechemicals (III): Stabilizationand treatment

By David Quigley,Fred Simmons, David Blair,Lydia Boada-Clista,Dan Marsick,Helena Whyte

INTRODUCTION

In two previous articles we discussedhow there are many misconceptionsconcerning time-sensitive chemicals1,2

and how time-sensitive chemicalsshould be managed. What remains tobe discussed is ‘‘How does one treat andstabilize time-sensitive chemicals thathave been stored for prolonged periodsand have developed additionalhazards?’’ That is the subject of thismanuscript. (Note: For the purpose ofthis manuscript, the term ‘‘expired che-mical’’ will refer to any time-sensitivechemical that has been stored for pro-longed periods and has developed addi-tional hazards that must be mitigated.)

Whenever an expired chemical isfound, it must be treated in order to

David Quigley (Y-12 National SecurityComplex).

Fred Simmons (Westinghouse Savan-nah River).

David Blair (Focus ManagementGroup).

Lydia Boada-Clista (DOE Ohio FieldOffice).

Dan Marsick (DOE-EH).

Helena Whyte (Los Alamos NationalLaboratory, Los Alamos, NM 87545,USA) (Tel.: (505) 667-2854; e-mail:helenaw@lanl.gov).

24 � Division of Chemical Health and Safety of the

Elsevier Inc. All rights reserved.

be rendered safe for disposal or furtheruse. Several steps are involved in thisprocess. First, one needs to identifypotential hazards. Second, determinehow the hazards can be mitigated.Third, necessary equipment andreagents for the process need to beidentified and procured. This meansthe work needs to be clearly under-stood and carefully planned. Thefourth step is the identification of thepersonnel who will perform the taskand the last step is the actual treatmentof the product that would includereadying it for final dispositioning.

HAZARD IDENTIFICATION—IF IT HASHAPPENED, THEN IT MUST BEPOSSIBLE

Assumptions used in the process todetermine hazards may appear to becontrary to those typically used whenperforming chemical research. Oneassumption used in performing chemi-cal research is that the information isnot valid or publishable unless it can berepeated. The assumption that must bemade in the area of treating time-sen-sitive chemicals to render them safe issimilar to ‘‘If it has happened, then itmust be possible.’’ If a reaction isreported to have occurred, then it mustbe assumed to be able to occur again.There are several reasons for thisassumption. One reason is that thesource term is undefined. Once a con-tainer is sealed, one does not knowanything about the conditions insidethe container prior to the next open-ing. One does not know if the productinside is dry, if the vapor concentrationis too rich or lean to burn, if oxygen ispresent or if the ‘‘goo’’ present in theground glass joint is grease or hazar-dous product A second reason is that

American Chemical Society

one never really knows if hazard miti-gation efforts (e.g., wetting dried picricacid in the threads of the cap) havebeen successful until after the con-tainer has been opened. A third reasonis that many ‘‘events’’ have beenreported involving time-sensitive che-micals. These ‘‘events’’ may be explo-sions involving peroxides, toxicproducts that have accumulated overtime which have led to exposures orcontainer over pressurizations that ledto container failure. Many times, theexact conditions and chemistry ofwhat occurred are unknown. If condi-tions inside the container that need tobe stabilized and rendered safe areunknown as were those conditionsinside a similar container that wasreported to be involved in an event,then the behavior of the container dur-ing stabilization cannot be predicted.For this reason, all potential hazardsmust be treated as being present,unless, it can be proven, without adoubt, that they are not present. If ithappened once, then it must beassumed to be able to happen again.Because of this assumption, one mustalways be conservative when treatingtime-sensitive chemicals to renderthem safe.

WORK PLANNING

Once potential hazards have beenidentified, the work needs to beplanned so that it can safely be per-formed. The work plan will defineequipment and reagents needed. Forexample, a glovebox needs to be pre-sent if the work needs to be performedin an anaerobic environment. If anexothermic reaction is possible, thenice or some other cooling materialsshould be present. If fire is a possibility,

1871-5532/$32.00

doi:10.1016/j.chs.2005.02.002

Figure 1. Sample PPE: flash suit, face shield, SCBA.

Once potentialhazards have beenidentified, the workneeds to be plannedso that it can safely beperformed. The work

plan will defineequipment andreagents needed.

Another issue thatshould be addressedin the work planningstage is where the

work will beperformed and howthe time-sensitivechemicals will betransported to that

location.

then provisions need to be made tocontrol any potential fire. If an ener-getic reaction is possible, then provi-sions such as working in a fume hood,behind a blast shield, working remo-tely, etc., should be evaluated. Provi-sions should always be made to ensurethat workers have the proper personalprotective equipment (PPE). ProperPPE could include ballistic fragmenta-tion suits, self contained breathingapparatuses (SCBAs) (with extra

Journal of Chemical Health & Safety, Janua

breathing air cylinders), face shields,gloves, eye protection, and flash suits(Figure 1).

One concept that should be followedis to ensure that extra equipment andreagents are obtained to perform thetask. For critical items such as coolingice and fire extinguishers, there shouldbe a substantial excess present. Itshould be noted that previous reportshave shown that peroxide concentra-tion measurements can be in error andcan indicate substantially lower levelsthan actually present.2 In these situa-tions, neutralization will involve moreperoxides than were previously mea-sured. This will result in much moreheat than initially anticipated beingreleased, which will require muchmore cooling (e.g., excess ice) to keepthe reaction under control.

Another issue that should beaddressed in the work planning stageis where thework will be performedandhow the time-sensitive chemicals willbe transported to that location. Areaswhere the work can be performed needto be identified and several considera-

ry/February 2006

tions are involved in the decision ofwhere the work should occur. One con-sideration is if the work could be per-formed at the work location withoutendangering otheractivities or workers.Another consideration would addresspotential hazards associated with trans-porting the time-sensitive chemicals tothe work area. If the product is danger-ous to move, then the possibility of

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treating it where it is currently locatedshould be evaluated. If a potentiallydangerous product must be moved,then it should follow a path that wouldprovide a minimum of risk to others.Movement and treatment of potentiallydangerous products could also be per-formed after hours or on a weekend tominimize the hazard to other workers.Another consideration involving theidentification of a suitable work areainvolves the size and accessibility.Work areas should not be crampedbecause a small work area will tend tomake any fires, explosions or toxicreleases, more dangerous for those pre-sent. Also, cramped work areas make itmore difficult to stage necessary equip-ment and supplies. If a temperatureexcursion is observed and ice is notimmediately and easily available dueto the cramped conditions, then thereis a greater chance of losing control ofthe reaction. Cramped work areas aremuch more difficult for respondersshould an upset condition occur. Emer-gency responders wearing SCBAs andother protective gear have a very diffi-cult time moving about in crampedareas. These difficulties will slow theirresponse andexacerbate consequences.Lastly, the potential work locationshould be evaluated to determine itsproximity to safety showers and eye-wash stations, support equipment andother hazardous work. Surroundingstructures need to be assessed to deter-mine the size of exclusion zone needed.For example, cement walls and cementblock structures require minimal exclu-sion zones, while wood or glass struc-tures may require more expansivezones. Exclusion zones typically usedare a ‘‘Hot Zone’’ where work is beingperformed; a ‘‘Warm Zone’’ for logisticsupport; and a ‘‘Cold Zone’’ for safetysupport and access control.

Training, experience, and other qua-lifications of individuals involved in thetreatment and stabilization of time-sen-sitive chemicals are other elements ofwork planning. All work should be clo-sely supervised by a person who has anin-depth understanding of the chemis-try of the product being treated. Thesupervisor should be present at all timesshould something unexpected occur.Additionally, workers should haveextensive experience in working with

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chemicals andequipmentwhiledressedout in associated PPE. The process oftreating and stabilizing time-sensitivechemicals should be considered andtreated as being an elevated risk opera-tion and not a place for novices or forthose who are learning the equipment.In the event of an upset, it is imperativethat the employees be well versed onhow the equipment and PPE functionso that they know how to properlyreact. Training that will provide a foun-dation for the necessary experienceincludes OSHA 40 hour HAZWOPERtraining, HazMat 40 hour techniciantraining, care and use of remote hand-ling equipment, chemistry and chemi-cal techniques, and SCBA certificationtraining. Additionally, workers andsupervisors should be well versed onthe chemistry of those products thatthey are going to treat and stabilize.Lastly, the amount of training (includ-ing apprenticeship) and experiencenecessary should be proportional tothe degree of hazard associated withthe treatment and stabilization work.Relatively simple work like thatdescribed later in this article can beperformed by readers with a fairamount of training and skill while otherprocesses, such as neutralizing etherscontaining peroxides, should be left upto professionals. If there is any questionabout the skill and training level neces-sary to perform this work, then alwayschoose the most conservative solution.This decision would also include whenone would decide to hire a contractor toperform the work.

TREATMENT/STABILIZATIONPROCESSES

The following are a few examples andshould not be considered as proce-dures for stabilization and treatmentprocesses. These examples have beenpicked to demonstrate how the processshould work and to provide an idea asto the amount of precautions that arenecessary to perform the work safely. Itshould be noted that there are manykinds of time-sensitive chemicals andthat treatment and stabilization pro-cesses for each is different. The exam-ples provided are for relatively simpletasks that could be performed by

Journal of Chemical H

experienced laboratory workers underthe supervision of a chemist.

Cellulose Nitrate

Cellulose nitrate is cellulose that hasbeen nitrated and the degree of hazardis related to the degree of nitration - thegreater the degree of nitration, thegreater the hazard. Legacy nitrocellu-lose may be found as old motion picturefilm stock. Nitrocellulose is typicallysold in several different forms. It canbe sold as a thick strip called ‘‘bark’’,which is treated as a flammable solid. Itcan also be sold as a wetted fibrousproduct that increases the flammabilityhazard should the wetting agent evapo-rate. Lastly, it can be sold as a solution.Numerous solvent mixtures, such asthose containing diethyl ether, tetrahy-drofuran, and amyl acetate, can beused and, when sold as a solution,may go by other names such as ‘‘collo-dian’’ or ‘‘parlodian.’’ Nitrocellulosecan become a time-sensitive chemicalwhen it is either purchased as a solutionor is dissolved into solution at the placeof work. Nitrocellulose solutions can bestored in bottles that have either a screwtop cap or a ground glass top. If thenitrocellulose is used and a portioncomes in contact with either the bottlethreads or the ground glass joint, thenthe solvent can evaporate over time andform a thin film. This thin film canbecome so friction sensitive that open-ing the container can cause the thin filmto ignite. While this reaction would notnormally be sufficient to cause the con-tainer to explode, it would be sufficientto ignite the flammable solvents presentin the container. (The assumption madein this example is that the nitrocelluloseis not dissolved in a solvent, such asdiethyl ether or tetrahydrofuran. Thesesolvents can form peroxides over timewhich would be an additional hazardrequiring a different stabilization/treat-ment process.)

In order to safely open containers ofnitrocellulose dissolved in a solvent,one must ensure that any nitrocellu-lose present on the threads of the bottleor in the ground glass joint is wettedwith solvent. Solvent that is present towet the nitrocellulose will act as alubricant and will render the nitrocel-lulose thin film less sensitive to fric-tion. Wetting the threads or the joint of

ealth & Safety, January/February 2006

Figure 2. Note the dark patches of sodium superoxide.3

the bottle will reduce or eliminate thepotential for a dangerous reaction tooccur. The preferred method for wet-ting the threads or the ground glass jointwould be to invert the container in areservoir using sufficient solvent toensure that the threads or glass jointsare completely covered. The reservoirshould be covered to prevent evapora-tion of the solvent. A desiccator jar withits lid can work well for this procedure.Most solvents that are used for thisprocedure have a low viscosity, there-fore, little time is required to wet thethreads or glass joint. Usually one hourwill be sufficient, however, one maychoose to allow an overnight soakingto ensure complete wetting when thethreads cannot be easily seen.

Once the threads or glass joints arewetted, the lids may be removed. Pre-cautions should still be taken to ensurethat a container does not ignite uponopening. Several methods are availableto perform this task. One methodwould be to attach clamps to boththe bottle and the lid and then burythe bottle in vermiculite or some othernonflammable packing material. Onceburied, the clamps can be used toremove the lid. If there is an initiatingspark, then the packing material willprevent a fire by preventing air fromcoming into contact with the con-tainer. A disadvantage to this processis that absorbent material can becomecontaminated with the organic solventand nitrocellulose, resulting in morematerial that would need to be dis-carded. A similar method would beto open the container under water.The disadvantage to this method isthe potential contamination of thewater with the organic solvent andnitrocellulose. A third, and likely thebest, method would be to transfer thecontainer to an inert atmosphere glovebox and then to open the containerinside the glove box using the clamps.The glovebox would provide physicalprotection from a minor explosion andthe inert atmosphere would ensure thata fire involving air trapped inside thecontainer would not be sustainable. Anadvantage to this method is that therewould be no possibility of contaminat-ing other products, such as packingmaterials or water, which would com-plicate clean up and disposal.

Journal of Chemical Health & Safety, Janua

Since the most hazardous portion ofthe work has been completed at thepoint the container is opened, the workwould be transferred to a fume hoodwhere manipulations can more easilybe carried out. Container contents canthen be poured into a large, plastic,wide-mouth bottle. Sometimes thesolution will be too viscous to pour.When this occurs, more solvent canbe added to reduce the viscosity. Extrasolvent should be used to rinse out bot-tles that contained the nitrocellulosesolutions and the rinsate added to theplastic bottle. Eventually, by addingmore solvent, the concentration of thenitrocellulose in the solvent should bereduced to less than 1% before sealingand sending off as waste for disposal.

There are a few qualifiers for thisprocess. First, this method is notintended for use on nitrocellulose con-tainers that are larger than 100 mL.Second, this method should NOT beused when diethyl ether, tetrahydro-furan, or any other peroxidizable sol-vent is involved. Experts should bebrought in to perform the work undereither of these circumstances. Third,the resulting solution should not bestored for a considerable time beforedispositioning it as waste. This methodshould be coordinated with a wastedispositioning company so that thetreated nitrocellulose can be removedshortly after it has been processed.

Sodium Metal

Sodium metal can react with oxygenover time to form sodium superoxide

ry/February 2006

(Figure 2). The superoxide of sodiumappears as a black coating on the sur-face of the metal and is a very strongoxidizing agent that can react violentlywith organic materials. Due to its reac-tivity, waste disposal is not an optionuntil the hazard has been mitigated.

Of the many methods available forneutralizing sodium superoxide, con-verting it to sodium alkoxide is one ofthe easiest and safest. This methodinvolves reacting the superoxide/sodium metal with an alcohol to formsodium alkoxide and hydrogen gas.Despite being a ‘‘safe’’ method for treat-ing superoxide-contaminated sodium,it still requires extreme caution.

This procedure is performed in a 5 or10 L flask or container with an orificelarge enough to introduce the metallicsodium/sodium superoxide. Borosili-cate glass is the material of choicefor the container since it is resistantto corrosive materials, such as sodiumethoxide, impervious to solvents suchas ethanol, and can tolerate elevatedtemperatures. The ideal reaction vesselwould be a two neck, 5 or 10 L, roundbottom flask with 24/40 ground glassjoints modified to have a large openingcapable of introducing the sodium (seeFigure 3). Provisions also must bemade to allow for a thermometer, con-denser, and a means for introducing aninert gas flow. If a round bottom flaskas described above is to be used, then athree neck Claisen adapter wouldwork well. (Note: One of the arms ofthe Claisen adapter would have a twoneck Claisen adapter present to pro-

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Figure 3. Set-up for converting sodium superoxide to sodium alkoxide.

vide a means for adding additionalethanol, should the need arise.)

Equipment should be set up in a fumehood and firmly clamped together asshown in Figure 3. The bottom of theflask should rest upon a magnetic stirrerso that a Teflon1 coated stir bar canturn freely inside the flask. One arm ofthe Claisen adapter should have a con-denser attached. Ice water should bepumped from a 5-gallon pail into thecondenser and extra ice should alwaysbe available. The condenser must bekept as cold as possible. An inert gas,such as argon or nitrogen, is required tosweep away any hydrogen that isformed and to keep the atmosphere inthe reaction vessel inerted. Care mustbe taken to ensure that the flow of gasdoes not become excessive (>2 SCF/hour) during the reaction. A 200 8Cthermometer should be inserted intoanother arm of the Claisen adapterwhile a dropping funnel is placed uponthe last arm of the Claisen adapter. Thisdropping funnel will contain the etha-nol that will be used in the reaction.

Personnel who will be performing theneutralization activities (especially cut-ting of the sodium) need to wear appro-

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priate PPE. The PPE would include at aminimum SCBA, body armor, full-bodyKevlar1 coveralls, Nomex1 hood, fullflash cover, Kevlar1 and nitrile glovesand heavy flash gloves. Additionally, aclass ABC fire extinguisher should beavailable. When sodium metal cutting isbeing performed, then a class D fireextinguisher or bucket of sand shouldbe available and the buddy systemshould be used.

Once the apparatus is set up, theprocess can begin. The first step is toplace the sodium into the flask. Some-times the sodium will be present inpieces that are too large to be used.These large pieces need to be cut intosmaller pieces. To do this, the sodiumshould be removed from the mineraloil using laboratory tongs and placedin a Pyrex1 baking dish that has suffi-cient mineral oil present to cover thesodium metal. The sodium can then becut into smaller pieces using a knife.(Some chemical references will reportthat this cutting method could result inexplosions, but this claim applies onlyto potassium metal.) Remove a piece ofsodium (approximately 50–75 g each)from the mineral oil by gently grasping

Journal of Chemical H

it with laboratory tongs and quicklyplacing it (without dropping it) in thereaction flask. (Care should be takennot to grasp part of the sodium that hasa heavy coating of superoxide present.)Replace the lid covering the orificeused to place the sodium into the reac-tion flask, allow the atmosphere tobecome inerted, and lower the fumehood sash to the point where maxi-mum air velocity is attained. Add etha-nol in the dropping funnel until thesodium is covered. The reaction shouldbegin as soon as the ethanol touchesthe metal. As the reaction proceeds,the sodium will float to the top of thesolution and, at this point, the stirrershould be started. As the reaction pro-ceeds, an off-white film will form onthe surface of the solution and thetemperature may increase noticeably.More ethanol should be added to coolthe reaction and to ensure that thesodium and the superoxides have beencompletely consumed. The reaction iscomplete when there are no pieces ofsodium floating in the solution and thetemperature has cooled below 90 8C(approximately 1 hour). At this pointthe mixture can be removed from the

ealth & Safety, January/February 2006

A program should beimplemented whereby

the minimumrequired amount ispurchased, storage

flask using due caution since thesodium ethoxide will be extremely cor-rosive. It can quickly cause severe skinburns or attack active metals such asthe aluminum on an aluminized flashsuit cover. Subsequent batches can berun using the same flask until allsodium metal has been treated.

and handling are welldefined, trainingis adequate, a

disposal path is inplace before the

chemical ispurchased and

allowed to developadditional hazards,and managementprovides full and

unwavering support.

CONCLUSIONS

As can be seen by the previous exam-ples, the treatment and stabilization oftime-sensitive chemicals requires safetymeasures that exceed the safety mea-sures that are normally required fortypical laboratory work. There are goodreasons for these conservative mea-sures.

To begin with, these are not routinetasks for most laboratory techniciansor chemists. The required training andPPE are generally not available. Also,the participants are typically notskilled in the subtleties of the treat-ment processes. For these reasons, oneshould not attempt to treat time-sen-sitive chemicals unless the treatment iselementary or unless one is veryexperienced in the treatment process.If one is not experienced in these treat-ment processes, then one should con-tract with a professional service.

Journal of Chemical Health & Safety, Janua

As can be seen by this and the twoproceeding manuscripts in this series1,2

on time-sensitive chemicals, it is veryimportant to properly manage time-sensitive chemicals. In the first manu-

ry/February 2006

script1 we demonstrated how danger-ous time-sensitive materials canbecome and in this manuscript we haveshown how dangerous it can be to ren-der them safe by treatment. These twoissues amplify the importance of time-sensitive chemical management as wasdescribed in the second manuscript.2

Managing these types of chemicalsshould not be a process of ignoringthem until you have to address them.A program should be implementedwhereby the minimum requiredamount is purchased, storageandhand-ling are well defined, training is ade-quate, a disposal path is in placebefore the chemical is purchased andallowed to develop additional hazards,and management provides full andunwavering support.

References1. Management of time-sensitive chemi-

cals (I): Misconceptions leading to in-cidents. (2004). Chem. Health Safe.2004, 11(5), 14–17.

2. Management of time-sensitive chemi-cals (II): Their identification, chemistryand management. (2004). Chem. HealthSafe. 2004, 11(6), 17–24.

3. Christopher Erzinger; Ken Niswonger.Colorado Department of Public Healthand Environment, 2003. Personal con-versation.

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