NSWC/WOL/TR 75-159

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S~WHITE OAK LABORATORY

(• SPONTANEOUSLY COMBUSTIBLE SOLIDS--A LITERATURE STUDY

1"i By_ • Elee.nore G. Kayser May 1975= • Carl Boyars

SI NAVAL SURFACE WEAPONS CENTER

WHITE OAK LABORATORYWHITE OAK, SILVER SPRING, MARYLAND 20910

SAPPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

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ANAVAL SURFACE WEAPONS CENTERIWHITE OAK, SILVER SPRING, MARYLAND 20910

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NOTICE

The contents of this report reflect the view of the Naval

Surface Weapons Center, which is responsible for the facts

and the accuracy of the data presented herein. The contents

do not necessarily reflect the official views or policy of

the Department of Transportation. This report does not

constitute a standard, specification or regulation.

This document is disseminated under the sponsorship of theDepartment of Transportation in the interest of informationexchange. The United States Government assumes no liabilityfor its contents or use thereof.

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UNCLASSIrILDSECURITY CLASSIFICATION Of THIS PAGE (Whetn Dmat Entered)

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'WNTANEGUSLY~~~N NOBUTILESOID Fna ed)t

/0 Eleo-nore G. /Kayser-. Carl /i~oyaxs =OTA-#4

S. PERFORMING ORGAPAIZATION NAME AND ADDRIESS I*. PROGRAM ELEMENT. PROJECT, TASKlAREAa *o JU~4 NUMBERS

I4. MONITRORLING AGENCY NAME AN ADDRESSt1dtemtfo iullm 01Ca 15SURT CLSSoftl eo)

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16. DISTRIBUTION STATEMENT (of thi eport)atOtrdI lc 0 'd~~en t. eol

I11. SUPPLEMENTARY NOTES -This research was monitored by the Department of Treasportation, Office ofAssistant Secretary for Environment Safety and Consumer Af!fairs., Office ofHazardous Materials, Wasahizeon, D.* C.

It. K(EY WORDS (Continue on reviers side It necesary and Identify by block number)

Pyrophoric Materials Hazardous MaterialsSpontaneously Combustible Solids Transportation HazardAir-Hazardous MaterialsWater-Hazardous Materials

20. ABSTRACT (Continueaon reverse side It necoseary and Identify by block number)

Existing information on spontaneously combustible solids including pyrophoric-air hazardous materials and water reactive materials has been reviewed. Perti-

nent data on (a) the causes and prevention of spontaneous combustion in organic[and inorganic materials due to air and water reactivity, (b) the application ofvarious mathematical trea~tments to spontaneously combustible materials, and (c)available test methods for assessing the flammable properties of spontaneouslycombustible materials, e.g., autoignition temperature and spontaneou~s heating

Lare als inclu ________________________________

DD IO"7 ' 1473 EII4OF I NOV SS IS OSSOLETE UCASFE

S/N 01 ~2O~4- ,,0,SECURITY CLA3SIFICATION OF THIS5 PAGE (Whe.n Date Xneerao/)

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L. SECURITY CLASSIFICATION OF TNW PAGEC1ThOfl Data Sntarad)

NSWC/WOL/TR 75-159 May 1975

Under Interagency Agreement DOT-AS-40049, the Naval Surface WeaponsCenter, White Oak Laboratory, has completed a literature surveyof all attainable data pertaining to spontaneously combustiblesolids including pyrophoric-air hazardous and water reactivematerials. All available hazard classification systems and testmethods releting to spontaneous combustion have been reviewed andevaluated. Pertinent data on (a) the causes and prevention ofspontaneous combustion in organic and inorganic materials due toair and water reactivity, (b) the application of various mathemati-cal treatments to spontaneous combustion, and (c) available testmethods for assessing the flammable properties of spontaneouslycombustible materials e.g., autoignition temperature and spontaneousheating are also included. This is the final report under thatagreement. Use of trade names herein does not constitute anyendorsement of the products named.

Julius W. ENIG /By direction

Si

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NSWC/WOL/TR 75-159

TABLE OF CONTENTS

TITLE PAGE

Introduction 1

Causes of Spontaneous Combustion 1in Some Organic Materials

Spontaneous Ignition--Mathematical 2Treatments

Flammability Determinations 3

Materials Subject to Spontaneous 6Heating

Air-Hazardous Materials 11

Water-Hazardous Materials 12 IConclus ion 23

References 25

LIST OF TABLES

L TABLE

1 Materials Subject to Spontaneous Combustion 13

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NSWC/WOL/TR 75-159

INTRODUCTION

The Department of Transportation'L Hazardous MaterialsRegulations Board is considering the adoption of regulations thatwould provide a more complete identification of the stabilitycharacteristics and therefore the potential hazards associated inthe transport of hazardous materials. A number of materials aredesignated as flammable solids on DOT's commodity list because ofa history of spontaneous ignition occurring either in transit, inhandling, or in storage.

Currently DOT/OHM has inadequate technical data to definequantitative criteria for the hazard classification of these materials.Thereforethere is need for a theoretical evaluation of materialswhich could be designated "spontaneously coiabustible." The purposeof this investigation is to provide technical background for use indeveloping regulations for the transportation of such materials.At present, there is neither international agreement on regulationsconcerning the shipment of flammable solids nor a standard classi-fication test method for flammable solids in the transportationregulations.

In DOT terminology, "flammable" characterizes a greater degreeof fire hazard than "combustible" (excluding spontaneously combustible).Spontaneously combustible materials differ from readily flammablematerials in that the latter will ignite within a specified timelimit (a few minutes) and burn rapidly when exposed to a specificignition source. Ignition sources include hot surfaces, hot filaments,flames, hot gases, electric sparks, and adiabatic compression ofthe material itself. Spontaneously combustible materials can inflameeven in the absence of what are normally regarded as ignition sources.Although one can regard such materials as a sub-class of flammablesolids and liquids (current regulations), many spontaneously conbustiblesubstances may not ignite within the specified time limit in a testdesigned to characterize flammable materials. This is especiallytrue when the heat-generating reaction in the spontaneously combustiblematerial is one involving bacterial action. Also, the test forflammable materials may be performed on a sample size which is lessthan the critical mass necessary for spontaneous combustion to occurin some substances.

Further sub-classification of spontaneously combustible materialsincludespyrophoric materials, i.e., those that will ignite spontaneouslyon exposure to air (air-hazardous material) and those that will igniteon contact with water or moisture (water-hazardous materials).

Causes of Spontaneous Combustion in Some Organic MaterialskR~ef: 1-13)"

Organic materials which are subject to spontaneous ignition at

ordinary ambient temperatures must have access to atmospheric oxygenor carry oxidizer in some reactive form and be raised to a kindlingor autoignition temperature by the exothermic reaction. Moisture is,in some cases of spontaneous combustion, essential for the resultingreaction. Bulk transport and/or storage may result in spontaneousignition in many agricultural products. I

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NSWC/WOL/TR 75-159

Low temperature oxidations of substinces such as beet sugar andcoal can be directly related to their adsorption capacities foratmospheric oxygen, with desorption of the oxidized products.Adsorption in general is accompanied by the liberation of energy inthe form of heat. The temperature increase depends on the rate ofheat transfer to the surroundings. Higher temperature acceleratesthe chemical reactions with adsorbed oxygen, which in turn provide aneven greater heat release. Thus, physical adsorption is followed bysubsequent chemical oxidation and spontaneous ignition if the heatis not dissipated to the surroundings sufficiently rapidly to prevertachieving the autoignition temperature in the material.

The oxidizing action of microorganisms in organic materials suchas hay and sawdust often produces the initial heat which eventuallyleads to spontaneous combustion. In this process, the product ischanged chemically and physically by bacteriological action.Fermentation and action by microorganisms can raise the temperatureto about 1300F, Chemical oxidation of fermentation products thenoccurs. When the temperature reaches 2120F, the microorganisms aredestroyed. Chemical action involving the cellulose can furtherincrease the temperature. If the heat cannot be dissipated to thesurroundings, the temperature within the material continues to

r rise and the rate of oxidation increases. Eventually the materialreaches its autoignition temperature, where combustion occurs. Ingeneral, the conditions essential for spontanecus combustion whereSbacteriological action is involved are an existing slow oxidationS•' and good heat insulation.

Spontaneous Ignition--Mathematical Treatments (Ref: 14-24)

Ignition produced by the generation of heat within a materialwhich is decomposing can be treated by thermal explosion theory.Frank-Kamenetskii's treatment is approximately valid for anyexothermic decomposition in which heat evolution obeys an Arrheniuslaw with a constant energy of activation to represent the dependenceof zero order reaction rate upon temperature. This Arrheniusrelationship of course does not hold for microbiological processes(and is questionable for many complex chemical processes). Walkerattacks the approximation involved in application of the binomialtheorem to the Arrhenius law by Frank-Kamenetskii. Walker's treat-ment relates critical size to critical ambient temperature forself-heated materials undergoing reactions of zero order even whenthe effects of temperature on reaction rate are non-Arrhenius.Van Geel, starting with the Frank-Kamenetskii treatment, introducesthe concept of a safe radius, that is, a critical dimension forwhich the temperature difference between the center of a self-heatingmaterial and its surroundings does not increase mure than 10*C duringthe storage period. He shows this to be useful over a considerable

i!i range of activation energy values.

All applications of mathematical treatments of spontaneousignition require a knowledge of the apparent activation energy ofthe overall heat evolution reaction or some other means of apecifying

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NSWC/WOL/TR 75-159

dependence of reaction rate on temperature. All involve an approxi-mation of zero order reaction kinetics. This is valid in generalonly for reactions in which nearly all the originally reactingsubstance is still prusent or else as an approximation for a specificinstantaneous state. Prediction of the likelihood of occurrence ofspontaneous combustion depends, in addition, on knowing the specificheat of the material, its bulk density, thermal conductivitycoefficient, heat transfer coefficient to the surroundings, andtemperature of the surroundings as well as the heat evolution rateper unit mass; it also depends, of course, on the amount andgeometric shape of the material undergoing self-heating.

Flammability Determinations (Ref: 25-35)

Spontaneous Ignition Temperature (Ref: 25-30)

The thermal properties of spontaneously combustible materialswhich are normally determined by the chemical industry include auto-ignition temperature and spontaneous heating. The autoignition orspontaneous ignition temperature is defined as the lowest temperatureat which a substance in either gas, liquid, or solid state, in thepresence of air will ignite after a certain delay without theapplication of any artificial means of ignition. Factors influencingautoignition temperatures include the size and shape as well as thephysical and chemical properties of the material being tested.Methods which have been emplcyed for the determination of spontaneousignition temperatures include (a) crucible methods--static (MooreApparatus, Krupp Ignition Meter, Jentzoch Ignition Meter and ASTM D2155-6,5) and dynamic (The Royal Aircraft Establishment (Farnborough)Spontaneous Ignition Temperature Apparatus), (b) dynamic tube methods,(c) bomb methods, and Wd) methods of adiabatic compression. Ofthe preceding methods, the crucible methods are by far the mostpopular (25).

The ASTM D 2155-66 may be used for the determination of theautoignition temperature of liquid or semiliquid petroleum productsin air at one atmosphere pressure using a sample ejected from ahypodermic syringe. In this method, a heated 200 ml Erlenmeyerflask of borosilicate glass containing air at one atmosphere pressureis used as the test chamber. This test is carried out in a darkenedroom. A small sample of the test liquid is introduced into the flask.The contents of the flask are inspected during the five minutesfollowing the sample injection. If autoignition occurs, a flameappears in the flask. Observations are carried out at a series oftest temperatures and with several sample sizes. The autoignitiontemperature is taken as the lowest temperature at which ignitionis observed (26).

Spontaneous Heating (Ref: 31-34)

The Mackey apparatus is considered a suitable general methodfor assessing the spontaneous heating and ignition hazards associatedwith the transport, storage and use of materials that are subject to

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NSWC/WOL/TR 75-159

atmospheric oxidation at ordinary temperatures (31-33). Thisapparatus and subsequent modifications are used to detect materials'susceptibility to spontaneous heating. In general, this deviceconsists of a water-jacketed cylinder, 4 inches in diameter and7 inches high, the top of which is closed by a cover. The cover ispierced by a central hole and by two draft tubes each 6 inches longand 1/2 inch in outer diameter. One of these tubes extends intothe cylinder and the other extends upward from the cover. A 30 gsample is placed on cheesecloth, which in turn is placed in ametal gauze cylinder (2 1/2 inches in diameter and 6 inches long,no. 12 mesh). The gauze cylinder is centered in the jacketedcylinder. Water in the jacket is brought to a boil, the sample onthe cheescloth in the gauze cylinder is introduced, and a ther-mometer is placed in the central hole (31). If the sample temperaturedoes not exceed 100*C within an hour, the material is judged safe withregard to tendency for spontaneous heating. A thermocouple withrecorder would provide a safer and more accurate test. The test isuseless for 2ubstances which ignite as a result of slow oxidation andfor materials where biological processes can cause spontaneous ignition.

There is currently, no standard method available for assessingextremely flammable solids (pyrophoric powders) which can ignitespontaneously on exposure to air at ambient temperature. A testdeveloped by the Bureau of Explosives (American Association ofRailroads) for pyrophoric liquids is considered by a United Nationsworking group to be adaptable to some solids but not to powderlikematerials. This method requires rather large quantitie3 of materialand involvea the use of a sawdust reacting medium, although theparticle size, moisture content, and type of sawdust are not specified.A maximum relative humidity of 75% is also specified, which accordingto the Bureau of Mines, may not be high enough to evaluate thepyrophoricity of some substances (34).

The Bureau of Mines has recently developed a method forevaluating the ease of spontaneous ignition of extremely flammablesolids by determining their ease of ignition using an environmentalchambr at high-humidity conditions. This method utilizes smallsamples at ambient temperature of 900 or 130OF and at varioushumidity condi.tions. The procedure calls for an environmental

chamber in which the relative himidity can be varied from 53-90%and controlled to within 1 5%. The sample is placed in the centerof a 4 in. diameter Zy 6 in. long glass reaction tube that is mountedvertically in the environmental chamber to minimize heat losses. Thereaction tube is open at both ends to permit circulation of air. Theextent of the reaction is determined by visual observations rid bymeasuring the temperature rise near the top of the sample bý-d using30-gage iron-constantan thermocouple. The output of the thermocoupleis then fed to a continuous pen recorder (34). Further developmentsof the basic test procedure as well as a hazard classification offlammable solids for transportation can bt Zound in reports preparedfor DOT by P. V. King and A. H. Lasseigne, DOT Report TSA-20-72-6, 1.972(NTIS:PB-220084) and R. Hough, A. Lasseigne and J. Pankow, DOT ReportTES-20-73-I, 1973(NTIS:PB-227019/AS) i

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N:SWC/WOL/TR 75-159

hn additional work on the hazard of flammable solids which furnishessupplemental information on important variables occurring in severalof the tests proposed by previous investigators can be found in areport recently prepared for DOT by C. B. Dale, DOT Roort TES-20-75-2,197.(NTIS: PB 240 878/AS).

For absolute assurance that a material does not represent aspontaneous ignition hazard in transport, an adiatatic storage testshould be carried out at the maximum ambient temperature the materialis likely to encounter and for the maximum period of time that itwill be in transit (plus any additional prior storage time). Failureto achieve autoignition under these conditions, which are equivalentto a mass so large that there is no heat loss from the center bythermal conduction, is conclusive evidence. One applicable apparatusis described in a report prepared for OECD by J. W. Hartgerink (ThermalAnalysis of Unstable Substances: The Exothermal Decomposition Meter,Ass. nr. 8357/9569, RVO-TNO, Rijswijk, The Netherlands, May 18, 1973).It may not be necessary to carry out full-term adiabatic storagetests on materials whose self-heating cvuld be established by smaller-scale screening tests such as Differe'1tial Thermal Analysis orDifferential Scanning Calorimetry, and the Exothermal DecompositionMeter of RVO-TNO.

Water Reactivity (Ref: 35)

Moisture-or water-hazardous materials react violently withwater, generating sufficient heat to ignite combustible containermaterials or the flammable gases generated by the reaction. Althoughthis hazard is recognized by various organizations, currently, thereis no generally accepted method to evaluate the water reactivity ofmaterials. A procedure for determining water reactivity by eitherad.ling a given weight of water to a given weit_4t of material or viceversa has been proposed by Mason and Cooper cf the Bur•-u of Mines (35).In either case, the rate of the temperature increase as well as thetotal temperature increase are recorded, and the gases evolved aresarmpled for analysis. The test apparatus consists of a samplecontainer (a pyrex tube 1 3/8 in. dia. and 10 in. long) imbedded toa depth of 3 1/2 in. in a block of insulating foam (polyurethaneor polystyrene) 3 in. square by 5 in. high. A thin piece of copper3/8 in. square and weighing 0.5 gm is silver soldered to the tip ofa chromelalumel thermocouple which measures the temperature rise.The thermocouple is placed in the pyrex tube so that the coppersquare is covered by the sample. The output of the thermocoupleis then fed to a recorder. See also DOT reports cited in Ref. 34 discussio

Using appropriate safety precautions, an initial estimate ofthe severity of the reaction is made by adding 5 gms. of water slowlyto 0.5 gm of material. The temperature rise is measured by adding10 gms of water elowly (10-20 sec) to 1,2.5,10 and 20 gins. suc-cessively of the sample, Measurements are continued until thetemperature peaks and then begins to drop. If 1,2, and 5 gms ofthe material give virtually no temperature inci-ease in 4 minutes,10 gms of water are added to 10 gms of sample and the temperature

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NSWC/WOL/ R 75-159

is mon•itored for ore hour to determine if a slow rea, ion occurs.If the reaction is not too violent, 10 gms of water are added to20 gms of the material to see if a temperature rise results. Thisprocedure may also be revers,'d by adding the material to the waterin the container (35).

If gas is evolved, a sample from the react4.ng material iscollected through a flexible needle inserted into the reactioncontainer to within approximately an inch of the reacting mixture.This sample is then analyzed on a chromatograph for flammable and/ortoxic gases (35).

Materials Subject to Spontaneous Heating (Ref: 1-12,36-97)

Organic materials subject to spontaneous heating which can becaused by bacteriological action include hay, straw, clover, malt,grains, tobacco, seeds, fodder, fish-meal, fertilizers, garbage,sugar, etc., (1-12, 36-39, 43). The phenomena of spontaneous ignitionin these materials exhibit considerable variation according to theirspecific natures and also the external influences to which they aresubjected such as moisture content, size, exposure methods (-fshipping and storage. The real danger of spontaneoiws ignitionusually occurs when the damp product is piled in large masses forstorage. Experiments performed by Rothbaum, have shown thatspontaneous ignition is most likely to occur in moist, permeablebiological materials at relative humidities in the ý5-97% range.An exception to this would be where the oxidation of unsaturatedoils is involved. At relative humidity values below 95t no:| appreciable bacterial action takes place. Fungi are known to grow•actively at relative humidities greater than 75%, although most

bacteria metabolise strongly only at relative himidities over 95%.

As 100% relative humidity is approached, a rapid rise in thermalconductivity due to water vapor transfer is noted. This is respon-sible for large heat losses, and therefore subsequent chemicalreactions will be less likely to exceed the microbiological max .mumtemperature limit of 76 0 C. The thermal conductivity of wet porousmaterials between 60°C-1000C has been found to be almost entirelycontrolled by the rate of water vapor transfer. At relativehumidity values nearing 100% the thermal conductivity of moistporous materials shows a very rapid rise with temperatilre. Therefore,a chemical reaction of low heat output will produce a temperatureincrease more easily when the relative humidity is appreciablybelow 100%. Thus it seems likely that the biological temperaturelimit would be passed only by materials in equilibrium withrelative humidity readings within a fairly narrow range of about93-97% (1).

Rothbaum has found that in the spontaneous heating of hay,which is in equilibrium with a relative humidity at 95-97%, microbialaction is responsbile for temperature increases to about 70 0 C.Chemical reactions (dependent on the presence of moisture) thenincrease the temperature to 1709C while further chemical oxidation

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NSWC/WC JTR 75-159

of the dry hay than leads to combustion (1), Although hgay willself-heat due to microbial action, il: has been proven that chemicalheating of hay is not necessarily dependent on previous biologicalactivity. Rothbaum has shown that; even without previous microbialaction, chemical heating can continue in hay for lengthy periodsand, under adiabatic conditions, will raise hay to its ignitionpoint. While the self-heating of hay has long been a subject ofconcern, spontaneous ignition has never occurred in hay containingless than 33% moisture (moisture expressed as % of dry weight).Therefore, moisture control of this material should eliminate thehazard of ignition.

The spontaneous combustion of sugar and bagasse (the crushedjuiceless remains of sugar cane as it comes from the mill) (40-43)has also been reported. The self-heating of these materials whichoccurred in storage bins and silos was found to be due to oxieationinfluenced by fermentation. Both Actinomycss and Semiclost-'-Tbacterial strains (bacteria which have been identified wit-fermentations which evolve heat) were found in the decompc .d sugarand also in the sugar from the edges of the affected area.ý.

Specific biochemical processes have a decisive significancein the phenomena of spontaneous heating of many materials. One of"these processes is the utilization of proteins and the products oftheir hydrolysis as a source of energy by microorganisms. Thechief energy loss in the decomposition of proteins as reported byGo Goldin, is connected not with hydrolysis but rather with thedecomposition of amino acids. The production of heat at the expenseof proteins and the products of their hydrolysis is much greaterunder aerobic than under anaerobic conditions. It is practicallyimpossible for the decomposition of proteins under anaerobicconditions to result in spontaneous heating since the production ofheat is related to oxidation processes. Certain organic acids,such as acetic, propionic, and ascorbic, are strongly inhibitoryto mold and bacterial growth. The calcium and sodium salts ofpropionic acid are normally used in fruits and vegetables to inhibit

Sthe growth of molds. Propionic acid has also been used to preventmicrobial deterioration in grain (moist wheat and cornmeal) for atleast twelve months if the pile is protected from the rain. Inaddition to being antimicrobial, propionic acid and its salts stop

* respiration of the living cells in stored grain, thereby inhibiting* any heat buildup in the pile.

Mixtures of nitrates with easily oxidized materials (fertilizermixtures) are also a recognized fire hazard due to their ability toself-heat. Excessive development of heat in curing piles offertilizers (44,45) containing superphosphate, organic matter, andlarge amounts of inorganic material can be traced to the oxidationof organic matter by nitric acid, which is formed in the reactionS btween the nitrate and free phosphoric acid. The rate of thereaction as reported by Davis and Hardesty, is accelerated byincreases in (a) concentration of free phosphoric acid in theliquid phase of the fertilizer, (b) size and insulating properties

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NSWC/WOL/TR 75-159

:of the curing pile, (c) amount and mobility of the liquid phase inthe mixi .re, and (d) degree of interaction among the active ingredientsof the mixture. The degree to which these conditions are fulfilledwill determine the extent of the temperature rise. Under certain

f - conditions the heat generated by the oxidation reaction is sufficientto cause spontaneous ignition in a base mixture stored at 30*C. Thereaction leading to ignition of such mixtures containing super-

iphosphate, ammonium nitrate, and organic conditioner can be preventedby treatment of the superphophate with ammonia (45).

Animal and vegetable fibers '3,10,11,46) such as wool, silk,cotton, lute hemp, flax, shoddy, etc., are also susceptible toautooxidation which can lead to spontaneous ignition. Animalfibrous materials are in general less susceptible to spontaneousignition than vegetable fibers, since hollow fibers (vegetablefibers) constitute a greater danger in their behavior toward firethan do solid fibers because of their tendency tc absorb oxidizingforeign materials. Animal fibers, in general, when ignited willnot support coiubustion while vegetable fibers will smolder andburn. Both animal and vegetable fibers which have been in contact

* with animal or vegetable oils are subject to self-heating and. spontaneous combustion.

Cotton waste (4,7,10,11) when in contact with fatty oils is moresusceptible to autoignition then animal fiber. The autoignition isdependent on the properties of the oils with which the fibers arein contact. The more unsaturated oils are the most hazardous becauseof their ease of oxidation. The presence of moisture is also anaggravating factor responsible for autoignition. Mineral oils whileless subject to oxidation because of their negligible affinity foroxygen, cannot be absolved from the autoignition hazard, althoughthey are sometimes used as a means of reducing the danger of Ispontaneous ignition by mixing with other more hazardous oils.

Although heat is developed by friction at baling, by bacterialactivity in wet wool, and by moisture adsorption on over-dried wool,direct oxidation of wool (47-53) seems to be the main processleading to temperatures high enough to cause ignition. Shearedand slipe wools (wools that contain little or no fat or oil) do notignite. Experiments by Walker, Williamson and Carrie et al., usingether-extracted fat from pie wools (wools removed from sheepskin bythe pie process contaminated with subcutanaeous fat) demonstratedthat the self-heating reaction is associated with the fat and notthe wool. The heating reaction in wool is caused by the atmosphericoxidation of unsaturated components of fat. it has been suggested

* 'that traces of water' vapor are necessary to catalyse this oxidation,however no such effect could be detected in experiments on driedwool by Walker and Williamson. However, the influence of water isrevelant to the problem. Bales of wet or damp wool can become hotdue to microbiological action. Microbiological heating of wet woolmust therefore be considered as a possible trigger mechanism topreheat bales of wool to a point where oxidation could commence,since previous experiments have shown that the oxidation of pie fat(fat extracted from pie wools) can take place in the presence of ccnsiderablemoisture.

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Soybeans a.id soybean by-eroducts (3,10,39,55-57) are an exampleof another common agricultural product in which spontaneous combustioncan occur. The oxidation and thermal polymerization of the unsaturatedoils present in soybeans (approximately 10 times as much unsaturatedoil as wheat) is considered responsible for the ease with whichchemical heating takes place. Although a high moisture content isconsidered a primary cause of spontaneous ignition in some agriculturalroducts 'hav, grains, fodder, etc.) the principle cause of spontaneous

ignition in soybeans and soybean by-products appears to be theoxidation anT poymeization of the unsaturated oils, with moistureconsidered a contributing factor. As in the case of other commonoxidizable vegetable oils, the actual spontaneous ignition hazardpresented by soybeans will depend upon the circumstances including(a) the amount of oil involved, (M) the ambient temperature (c) theconditions with respect to heat transfer and dissipation and (d) thepresence of other combustible materials.

Clay-diluted chlorinated insecticides (54) occasionally decompose,sometimes becoming sufficiently hot to ignite spontaneously. The

decomposition of insecticides occurs in wettable powders and dustsas a result of the catalytic action of the clay diluent. Investiga-tions have shown that this decomposition is promoted by the acidsites of the clay. The rates of reaction of these insecticidesin the presence of various clay diluents were found to increasewith the increasing acidity of the clay surface. Treatment of theclays with volatile organic' bases or basic substances such as ureaor hexamethylenetetramine, has been found to reduce the acid strengthand diminish the rate of decomposition accordingly. Since theintroduction and use of these clay-deactivators, the problem ofdecomposition has virtually disappeared.

Animal and vegetable oils (10,25,58-60) in the presence of airand at sznbient temperatures, undergo oxidation with the evolutionof heat. Although their ignition temperatures are comparatively high,the heat generated by oxidation is sufficient in some cases to causeignition under favorable circumstances. This susceptibility tospontaneous ignition is greatly increased by exposing a relativelylarge surface area of the oil to the oxygen in the air (e.g.,impregnating a waste material such as sawdust, cotton, rags, etc.).The form in which the oily fibrous material is exposed to the airalso influences the reaction and affects the rate of dissipation ofheat. If the oily mass is compact, the oxygen supply from theatmosphere is necessaril-', restricted, and if exposed to air currents,the heat loss may prevent a rise in temperature. However, a reaction

can begin (given enough oxygen) that can generate considerable heatwhich is accumulative due to the insulating power of the waste andthis heat can then accelerate further reaction and finally result

4 in ignition.

Arailable evidence indicates that wood when subjected tocontinuous heating will form a pyrop•'-ric type carbon which isliable to ignite spontaneously at low temperatures. Sawdust andwood chips (10,11,61-75) also have a tendency to spontaneously

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ignite when stored in large piles. This tendency is increased whenthe materials are impregnated with vegetable or animal oils, glue,organir c dyes, etc. Nitric acid which fosters internal heating andcombustion can also cause spontaneous combustion in sawdust. Thein.itial heat re2 ease in a chip pile is the result of Oxdaitiveprocess3es occurr.-ng within or on the surface of the wood chips.This heating is the direct result of (a) respiration of the livingcells, (b) bacterial growth-micioorganisms on or within the woodindirectly oxidizing the various wood constituents, (c) directchemical oxidation - readily oxidizible materials such as unsaturatedfatty acids and other extractives entering into combination withatmospheric oxygen by direct chemical reactions, and (d) fungalgrowth. The initial heating observed in the first few days of chipstorage is apparently caused predominately by (a), (b), and (c).The direct chemical oxid.zations probably become important above42WC. The contribution of fungal growth to the heating observed inwood chips is most likely significant only after everal weeks ofoutside storagc. Several factors which influence these oxidativeprocesses include (I) chip pile temperature, (2) species of wood,

4 (3) moisture content, (4) climatic conditions, (5) pile size andKheight, and (6) the amount of foreign material. Losses in wood[substance from the a-tion of microorganisms in wood chips stored

outside average roughly about 1%/month, although these losses canrange as high as 2.5-3.0% in the South. Propionic acid, a biocideused successfully to protect stored grains from microbiological

;J attack and from destructive self-heating, can be absorbed by woodSchips and effectively prevent the fungal degradation of the chips.The cost for the quantity of acic required to protect chips duringoutside storage is high.

Wood fiber insulating boards (8,11,12) have been ?now to undergospontaneous ignition, while in transit, Iue to insufficient coolingafter drying. This hazard can easily be eliminated by maintainingsufficient moisture and by cooling the boards before stacking, rolling,and shipping.

Pa__er rolls (2300-2800 ibs.) (7,11,61) are also subject tospontaneous combustion while in transit. This can be due to severalfactors (a) very dry rolis (C)-3% moisture), (b) tight winding ofthe rolls, (c) size, and (d) a high initial temperature. This hazardcan also be eliminated by increasing the moisture content to 5% orgreater.

The spontaneous combustion of co&l (10-12,76-97), has been atopic of interest and difficulty for t-Fe past two centuries. Thefactors which are generally agreed to have the greatest effect onthe oxidation rates and ignition temperatures in coal are: (a)particle size and pore structure -- the ignition temperaturegenerally decreases with decreasing particle size and oxidationrates generally increase with decreasing particle size, (b) oxygenconcentration--increasing oxygen concentration increases the oxidationrate and decreases the ignition temperature of a particular coalsample, and (c) amount of volatile matter -- as the volatile matter

12

NSWC/WOL/TR 75-159

increases, the ignition temperature decreases and the rate of oxidationalso tends to increase. Moisture also plays a pronounced role inthe oxidation of coal. The effect of moisture in favoring the oxi-dation and self-heatini of coal has been confirmed by variousresearchers. It is evident from both practical anI experimentalstudies that coal-oxygen complexes are formed when freshly powderedcoal is exposed to air at ambient temperatures. These oxygenatedcomplexes are unstable and readily decompose to oxides of carbonand water. The presence of adsorbed water has been proven to be anecessary condition for the formation of these complexes, whichappears to be an essential step in the overall cxidation processof coal. Preventive measures include (a) ventilation, (b) limitedmass, and (c) low temperature immersion carbonization -- immersingthe coal for short periods (5-15 minutes) in an inert liquid such assilicone oil at temperatures between 350-460 0 C. This carbonizationtechnique effectively reduces the accessible pore volume of thecoal to levels at which heat generation through subsequent sorptionof moisture and oxygen is too slow to cause significant temperaturerises in a stockpile. It has also been established by infraredspectroscopic scanning of the washed coal samples that little ifany oil penetrates into the coal during the immersion heating process (95).

Chemically activated carbon (11,79,88-94) is known to undergoself-heating and ignition in transit and therefore must be adequatelycooled before it can be shipped and stored safely in bulk. Availablestudies on charcoal and activated carbon show that the self-heatingis principally a consequence of tht occlusion of oxygen. Moisturecontributes significantly to the initial stages of self-heating ofdry material at ordinary temperatures. The self-heating characteristicof powdered activated carbons is also dependent on their manufacturingprocess, e.g., steam activated or chemically activated. The use ofpolyethylene liners or covers where practical, has proven successfulin the prevention of self-heating by restricting the flow of airthrough these oxygen sensitive materials.

Lampblack (11,79) is subject to the same conditions only to agreater degree. Ignition is fostered by its oily character. Lamp-black from tar, tar oils, mine:.al oils, coal lignite, and peatcontains sulphur which on contact with iron can spontaneously ignite.Storage and transport in large heaps should be avoided as far aspossible. Careful handling of this material can eliminate the dangerof spontaneous combustion.

Air-Hazardous Materials (Ref: 10,98-104,128,130,133, 140)

The exposure of a relatively large surface area of some metalse.g., titanium, zirconium, iron, promotes its rapid reaction withthe oxygen of the aic causing spontaneous combustion. It has beensuggested that there is a great probability that all metals becomepyrophoric when the ratio of surface-to-volume becomes sufficientlyhigh (98). By decreasing the particle size, the ratio of surfaceto mass increases and the reaction (oxidation) on the surfacegenerates more heat per gram, resulting in a larger rise in temperature.

13

NSWC/WOL/TR 75-159

The degree of a material's pyrophoricity is critically dependent onits particle size. Pyrophoric action results from the inability ofa material to dissipate its heat of oxidation (even slow oxidation)in air rapidly enough, thus causing a rapid rise in temperature (100).The large amounts of heat liberated during oxidation of a pyrophoricpowder caii also cause explosion if the powder is suspended in airas a dust. Pyrophoric action is not limited to powders of sub-stantially pure metals but includes compounds as well as alloys.This behavior occurs in the lower oxides of iron, manganese, anduranium, the hydrides of uranium and cerium, and the carbides andnitrides of uraniv'm. It is generally true that the higher the heatof formation of the metal oxide, the larger the particle size maybe and yet retain the ability to burn spontaneously. Almost anyalloy or compound will be pyrophoric if it is in fine enoughparticles and if its heat of oxidation is strongly exo''hermic (100,103). Examples of other pyrophoric noaterials include (a) metalalkyls -- trimethyl aluminum, triethyl aluminum -- compoundscontaining a very active organometallic bond capable of highSreactivity with oxygen, (b) metal carboryls -- iron pentacarbonyl,potassium carbonyl, and (c) metal hydrides -- aluminum hydride,barium hydride, beryllium hydride. Pyrophoric substances can beinactivated by opening the container under liquids such asacetylcellulose in acetone, 96% ethyl alcohol, and in the case ofpyrophoric cobalt, even hydrocarbons. On evaporation of thesolvent, the pyrophor is protected against spontaneous ignitionby surface oxidation which occurs during the slow evaporation ofthe solvent.

Water-Hazardcus Materials (Ref: 103,111,121,127,130,140)

In general, active metals, hydrides, carbides, and phosphidesare incompatible with water because of thý- generation of flammable,toxic, and/or explosive products. Cesium, potassium, sodium, and thealloys of these metals can ignite spontaneously on exposure to airand/or moisture. The degree of hazard depends to a great extent onthe probability of collecting a dangerous concentration of flammableproducts. This depends on factors such as quantity of materialinvolved, ventilation, etc.

The following table (Table I) lists solid substances that are* subject to spontaneous ignition as well as materials that are

flammable due to reaction with air (air hazardous materials) and/ormoisture (water hazardous materials). The hazardous materiallisting reported in Table I is compiled from data obtained from theopen literature, the Code of Federal Regulations (CFR-49) 1972, andthe Qransport of Dangerous Goods (1970) - United Nations recommen-dations, as well as unclassified government reports.

14

rt

NSWC/WOL/TR 75-159

TABLE 1

Materials Subject to Spontaneous Combustion (105-130,137-141)

MATERIAL REMARKS: Accelerene (para nitroso dimethyl

aniline) spontaneously flammableAlfalfa Meal subject to spontaneous ignition"Aluminum - Triethyl, Methyl,

Palmitate, Diethylmonochioride spontaneously flammableAluminum - Dust, Powder, Hydride spontaneously flammable in airAluminum Phosphide on reaction with water yields

phosphine which is spontaneouslyflammable

Aluminum - Carbide, FerrosiliconPowder water hazardous material

Aluminum Silicon Powder water hazardous materialAzido Thallium explodes in air

Bags, Used Burlap, Jute tendency to ignition dependent onprevious use

Barium spontaneously flammable in moist airBarium Azide spontaneously flammableBarium Carbide spontaneously flammable on contact

with waterBarium Hydride- Fine Powder can spontanecosly ignite in dry and

moist airBarium Perioxides can react explosively with large

quantities of waterBarium Sulfide can ignite in dry and nioist airBeans - Locust, etc. subject to spontaneous combustionBenzyl Sodium spontaneously flammableBeryllium Powder spontaneously flammableBeryllium Dimethyl spontaneously flammable in moist airDis-Cyclopentadienyl Manganese spontaneously flammable in moist airBismuth spontaneously flammableBismuth Ethyl Chloride spontaneously flammableBismuth Pentafloride reacts violently with water sometimes

with ignitionBone Meal, Bone Black, Bone

Charcoal subject to spontaneous combustionBorohydrides of Al,Be,Zr,Hf spontaneously flammable in airBoron Dust spontaneously flammable in airBoron Chloride Tetramer spontaneously flammable

Cacolyl Cyanide spontaneously flammableCacodyl Phenyl s' •ntaneously flammableCadmium spontaneously flammableCadmiunm Amide can explode in waterCadmium Nitride spontaneously flammable in water

15

.- . . . . . . AL -

NSWC/WOL/TR 75-159

TABLE 1 (Cont.)I MATERIAL REMARKCS

Calcium Carbide yields C2H2 on contact with waterwhich can ignite

Calcium Hydride dust can explode if dispersed in airCalcium Hypochlorite decomposes in water, vapors produced

are flammableCalcium Metal finely divided material is

spontaneously flammable in airCalcium Nitride spontaneously flammable in airCalcium Oxide violent reaction with water sometimesl with ignitionCalcium Phosphide reacts with water yielding phosphine

which is spontaneously flammableCalcium Silicide spontaneously flammableCalcium Silicon (Calcium

Manganese Silicon) spontaneously flammableCalcium Sulfide spontaneously flammableCalcium Dithionate spontaneously flammableCelluloid, Scrap subject to spontaneous ignitionCerium spontaneously flammable in airCerium III Aluminohydride spontaneously flammableCerium Amalgam spontaneously flammable in airCerium Hydride Amalgam spontaneously flammable in airCerium Indium Alloy spontaneously flammable, 0-30% Ce

alloy has greatest pyrophoricityCerium Nitride spontaneously flammable in moist air

H Cesium Amide possible explosion on contact withwater

Cesium Antimony Alloy spontaneously flammableCesium Arsenic Alloy spontaneously flammableCesium Bismuth spontaneously flammableCesium, Metal spontaneously flammable in moist air

at room temperatureCesitnu Oxide spontaneously flammable in waterCesium Phosphide spontaneously flammable in moist air

and on contact with waterCesium Silicide ignites spontaneously on contact

with waterChromium spontaneously flammableChromium Cobalt Alloy spontaneously flammable when particle

size is less than 1 micronC'Cromcus Monoxide spontaneousCoal - BituminouQ- brown, subject to spontaneous ignition,

fossil tendency to self-heating depends onorigin, nature and degree ofvolatile ingredients

16

NSWC/WOL/TR 75-3159

TABLE 1 (Cont.)

MATERIAL REMARKS

Cobalt spontaneously flammableCobalt Amalgam spontaneously flammableCobalt Nitride spontaneously flammableCobalt Resinate spontaneously flammableColophony Powder, Gum Rosin subject to spontaneous combustionI Copper fine powders are spontaneously

flammable (.01-.03 microns)Copper Aluminohydride spontaneously flammableCopper Pyrite or Copper Ore in large bulk - subject to

Concentrates spontaneous ignitionCopra subject to spontaneous ignitionCork subject to spontaneous ignitionCotton, Cotton Waste, Wet Cotton subject to spontaneous ignitionCupric Phosphide spontaneously flammable in moist air

and on contact with water

Decaborane spontaneously flammable in airDibutyl Magnesium spontaneously flammableDiethyl Magnesium spontaneously flammable

Diethyl Zinc spontaneously flammableDimethyl Magnesium spontaneously flammableDiemthyl Zinc spontaneously flammableDipotassium Nitroacetate explodes when in contact with waterDisilyamino Dichloroborine spontaneously flammableDistillers Dried Grains subject to spontaneous ignition,

maintain moisture content between7-10% and cool below 1000 F beforestorage

Disulphur Dinitride explodes in air above 30*CDust from blast furnace filters subject to spontaneous ignition

Ethyl Lithium spontaneously flammableEthyl Sodium spontaneously flammableEuropium oxidizes rapidly in air and may ignite

apontaneously

Feeds, various subject to spontaneous ignitionFerrosilicon - containing

>30% and <90% silicon ignites on contact with waterFerrous Oxide spontaneously flammable in airFertilizers, Manure subject to spontaneous ignitionFibers - Bast, Cocoa, Coir,

Esparto, Flax, Hemp, Jute, subject to spontaneous combustion,O'ikum, Palmetto, Sisal, etc. safe moisture content <6>20%

F_' is - if base is nitro-ce. lulose subject to spontaneous ignition

Fish Meal, Fish Scraps subject to spontaneous ignition, safemoisture content between 6-12%

17I

____

NSWC/WOL/TR 75-159

TABLE 1 (Cont.)

MATERIAL REMARKS

Grains, various subject to spontaneous ignition

Hafnium spontaneously flammableHay subject to spontaneous ignition

moisture control will eliminatethis problem

Ilexachlorethane Mixture spontaneously flammable on contactwith water

Hexamino Calcium spontaneously flammableHides, various subject to spontaneous combustion

Indium Monoxide spontaneously flammableIron - filings, turnings, subject to spontaneous ignition when

borings, powder, scrap, chips present in large bulk, also whenwool, etc. camp can under certain conditions

liberate hydrogen which is ilammableand explosive on mixture with air

Iron Amalgam spontaneously flammable"Iron II Hydroxide spontaneously flammable in airIron Pyrite, Iron Sulphide, Iron

Disulphide subject to spontaneous ignition inlarge bulk

Iron Oxide, spent or Iron Sponge,spent subject to spontaneous ignition

Ixtle subject to spontaneous combustion

Jaggery or Jaggery Sug.r subject to spontaneous combustion

Lamp Black subject to snoitaneous ignitionLanthium Antimony Alloy spontaneously flammableLead pyrophoric powder produced from I

Fe(QH) 3 if reduction temperature islower than 550 0C

Lead Imide explodes on contact with waterLithium Aluminum Hydirii reacts with water and moist air

forming hydrogen which is spon-tanejus ly flammable-

- Lithium Borohyeride spontaneously flammable on contactwith moist air end water

Lithium Dimethylamide spontaneously flammableLithium Hydride spontaneously flammableLithium Hypochlorite flammable on contact with waterLithium Metal spontaneously flammable on contact

with moist air and waterI Lithium Nitride spontaneously flaxraable on contactwith moist a:.r and water

18

NSWC/WOL/TR 75-159

TABLZ 1 (Cont.)

MATERTAL REMARKS

Lithium Phosphide spontaneously flammable in moist airSrand on contact with water

Lithium Silicide spontaneously flammableLycopoditxm, Club Moss Seeds,

Earth Moss Seeds, Vegetable can spontaneously ignite when scatteredSulphur in air

Magnesium Aluminum Phosphide spontaneously flammable on contactwith water

Magnesium Cyanide spontaneously flammable on exposureto air

Magnesium Diamide spontaneously flammable on exposureto air

Magnesium Diphenyl spontaneously flammable on contactwith moist air and water

Magnesium Ethyl spontaneously flammable in airMagnesium Hydride spontai )usly flammable on contact

with itoist air and tap waterMagnesium, metal-powder, ribbon, reacts with air and moisture evolving

chips H2 which ignites spontaneouslyMagnesium Methyl spontaneously flammable in airMagnesium Phosphide spontaneously flammable on contact

with waterManganese II Aluminohydride spontaneously flammableManganese Bismuth Alloy spontaneously flammableSMethyl Aluminum Sesquibromide spontaneously flammable .

Methyl Aluminum Sesquichloride spontaneously flammableMethyl Magnesium Chloride spontaneously flammableMethylene Dilithium spontaneously flammable in airMethylene Magnesium spontaneously flammableMethyl Lithium spontaneously flammable

Methyl Sodium spontaneously flammableMolybdenum Metal spontaneously flammableMolybdenum Dioxide spontaneously flammableMolybdenum Trioxide spontaneously flarmnableMonomers - for polymerizations subject to self-heating from spon-

taneous polymerization caused byheat and light

Nickel - Finely divided, activatedor spent, wetted with not lessthan 40%, by weight, of water or spontaneously flammable (.01-.03other suitable liquid microns)

Nickel Carbonyl in the presence of air forms a depositwhich becomes peroxided which thentends to decompose and ignite

Nickel Iron Alloy spontaneously flammableNickel Lanthium Alloy spontaneously flammable

19

NSWC/WOL/TR 75-159

TABLE 1 (Cont.)

MATERIAL REMARKS

Oils, animal and vegetable* subject to spontaneous ignitionOleic Acid impregnated fibrous materials may

self-heat unless ventilatedPaper, waste paper - treated

with unsaturated oils,incompletely dried (includescarbon paper) subject to spontaneous Ignition

Pentaborane spontaneously flammablePhenyldiazosulfide explodes when dried in airPhenyl Magnesium Chloride spontaneously flammablePhenylsilver explodes at room temperaturePhosphorus red-commercial subject to spontaneous ignition in

thick layers, critical thickness oft layer defined by Y-2X=[K(To-Ta)/Q]/ 2

where Y - critical thickness of layera in centimeters, above which spon-taneous combustion occurs, X - dis-tance in cm from plane of wax,

heat transfer coefficient,To = autogenous temp., Ta = ambienttemperatu-e, Q = heat of reactionin cal/cc/sec. The thickness of thelayer above which spontaneous ignitionoccurs is inversely proportional tothe temp. of the rate of generationof heat which is directly propoztionalto the rate of oxidation of redphosphorus.

Phosphorus white or yellow spontaneously flammable in air at 340C,preserved under water

Phosphorus Pentasulfide spontaneously flammable, can ignite oncontact with nmoisture

Plastics subject to spontaneous ignitionPlutonium explosive reaction with water, ignites

syontaneously in dry airPlutonium Hydride spontaneously flammablep-Nitrosodimethylamiline spontaneously flammablePotassium spontaneously flammable in air, also

possibility of explosionPotassium Antimony Alloy spontaneously flammablePotassium Arsenic Alloy spontaneously flammable

*Some of the more common animal and vege-able oils in decreasing tendencyto spontaneously ignite -- cod liver oil, fish oil, linseed oil, menhadenoil, perilla oil, > corn oil, cottonseed oil, olive oil, pine oil, red oil,soybean oil, ting oil, whale oil > castor oil, lard oil, black mustard oil,oleo oil, palm oil, peanut oil, -- avoid contact with any fibrouscombustible ma-arials.

20

NSWC/WOL/r:R; .5

TABLE 1 (Cont.)

MATERIAL REMARKS

Potassium Borohydride spontaneously flammable in waterPotassium Carbide explosive reaction on contact with

waterPotassium Carbonyl detonates on contact with air and waterPotassium Chlorate spontaneously explosivePotaJ3ium Dithionite spontaneously flammablePotassium Graphite spontaneously combustible in airPotassium Hydride spontaneously flammiable in airPotassium Metal Alloys spontaneously flammable in waterPotassium Nitride spontaneously flammable in airPotassium Nitromethane spontaneously flammable in waterPotassium Peroxide spontaneously combustible and possibly

explosive on contact with waterPotassium Phosphide spontaneously flammable in moist air

and on contact with waterPotassium Silicide ignites explosively on contact with

waterPotassium Sodium Alloys water reactive materialPotassium Sulfide may ignite spontaneously in air when

anhydrous or containing < 30% waterof crystallization

Prosiloxane spontaneously flammable in air

Rags, used spontaneously combustible tendencydepends on previous use

Rubidium ignites in air and on contact withwater

Rubidium Antimony Alloy spontaneously combustibleRubidium Arsenic Allo7 spontaneously combustibleRubidium Bismuth Alloy spontaneously combustibleRubidium Hydride spontaneously flammable in moist air

and waterRubidium Phosphide spontaneously flammable in moist air, and waterRubidium Silicide spontaneously flammable in moist air

and water

Samarium Carbide evolves acetylene and hydrogen oncontact with water

Samarium Dichloride evolves acetylene and hydrogen oncontact with water

Sawdust subject to spontaneous combustionScrap Leather subject to spontaneous combustionScrap Rubber subject to spontaneous combustionSeeds, seed cakes, seed

expellers - containingvegetable oils subject to spontaneous uohibustion

Silicides (of light metals) decompose in water yielding hydrogenSilicocyn spontaneously flammable

2.L

NSWC/WOL/TR 75-159

TABLE 1 (Cont.)

MATERIAL REMARKS

Silicon, dust spontaneously flammableSilicon Hydride spontaneously flammable in airSilicon Monoxide spontaneously flammable

Siloxane spontaneously flammableSilver-fine powder spontaneously flammableSoap Powder subject to spontaneous combustion when

uninhibitedSodium Acetate possibility of spontaneous ignition

%then in contact with moist air orwater

Sodium Aluminum Hydride spontaneously flanmmabie in waterSSodium Amalgam spontaneously flammable on contact

with moist air and waterSodium Amide ignites spontaneously on contact with

V waterSodium Borohydride ignites spontaneously on contact with

• waterSodium Carbide explosive reaction on contact with

"waterSodium Carbonyl detonates in air and waterSodium Dithionate may ignite on contact with waterSodium Dithionite (Sodium

Hydrosulphite) may ignite on contact with waterSodium Hydrazide spontaneously flammable in moist air

and waterSodium Hydride spontaneously flammable in moist air

and waterSodium Hydroxylamine spontanecusly flammable in air 4Sodium Lead Alloy spontaneously flammable in water and

moist airSodium, Metal decomposes in water forming hydrogen

which ignites spontaneously

Sodium Nitromethane spontaneously flammable in moist airSodium Phosphamide spont neously flammableSodium Phosphide rear with water and moist airSodium Potassium Alloy spo neously flammable on reaction

Swi--i waterSodium Silicide, powder spontaneously flavinmable in moist air

and possibly explosive on contactwith water

Sodium Sulfide spontaneously flammable in airStannic Chloride reacts with water and evolves con-

siderable heatStannic Phosphid3 spontaneously flarmable on contact

with moist air and waterStearic kcid heats spontaneouslyStraw of Flax, Maize, Oats, Rice, subject to spontaneous heating and

Rye, Wheat, etc. combustion

22

NSWC/WOL/TR 75-159

TABLE 1 (Cont.)

MATERIAL REMARKS

Strontium Azide spontaneously flammableStrontium Metal if finely divided ignities on expo-

sure to air, also liberateshydrogen on zontact with water

Strontium Phosphide spontaneously combustibleSulfur possibility of spontaneous ignitionSulfur Trioxide violent reaction with water

Tankage subject to spontaneous combustionTextile Waste, wet subject to spontaneous combustionTetrabromosilane violent reaction with waterThorium Hydride spontaneously flammableThorium, metal spontaneously flammable (high as

powder, moderate as chips)Thorium Nitride snontaneously flammable in airThorium Oxysulfide spontaneously flammable in airThorium Silver Alloy spontaneously flammableTin spontaneously flammabl," when finely

dividedTitanium Bichloride spontaneously flammable in air and

waterTitanium Bromide spontaneously flammableTitanium Carbide, dust spontaneously flammable in airTitanium Chloride spontaneously flammable in moist airTitanium Dibromide spontaneously flammable in moist airTitanium Diiodide ignites in moist airTita*ium Monoxide spontaneously flammableTitanium Trichloride spontaneously flammable in airTriazide Borine spontaneously flammable in air and

waterTr =hlorosilane reacts with waterTriisobutyl Aluminum subject to spontaneous combustionTriphenylaluminum decomposes explosively in waterTungsten,8 spontaneously flammable

Uranium Bismuth Alloy spontaneously flammable, over 30% U(very pyrophoric

Uranium Borohydride spontaneously flammable and liableto detonate in air

Uranium Carbide spontanecusly 1lammable if particlesize < 40 microns

Uranium Hydride spontaneously flammableUranium Metal, powder spontaneously flammable, if dry

ignites in air, if dispersed itcan explode in air

Uranium Monocarbide spontaneously flarnmab]'q, if < 40microns - very pyrophoric

S Uranium Nitride spontaneously flammableUranium ONide spontaneously flammable

23

-.. . - '.. at..& n •i •r . " .... --

NSWC/WOL/T." 75-159

TABLE 1 (Cont.)

MATERIAL REMARKS

Vanadium Sesquioxide spontaneously flammableVarnished Fabrics subject to spontaneous comrn ;tion

Wood - chips, excelsior, sawdustshredded wood, wood flour,wood shavings, wood wool subject to spontaneous combustion

Wool subject to spontaneous combustion

Zinc Dithionite spontaneously flammableZinc Metal, dust, ashes, powder

filings, dross, chips, shavings, in the damp state may heat spontaneouslyetc. and ignite on exposure to air

Zinc Phosphide spontaneously flammable in moist airZirconium spontaneously flammable in airZirconium Borohydride spontaneously flammableZirconium Carbonitride spontaneously flammable in airZirconium Dibromide spontaneously flammableZirconium Metal, powder sponge,

strips, coiled wire, sheets,etc. sponteneously flammable in air

Other materials subject to spontaneous combustion include: dess'ccatedleather, leather scraps, dried blood, dried blood tankage, garbage 1

• t~unkage, leather meal, slaughter house tankage -- liable to spon-¶ taneously ignite which is dependent on (1) composition of the products,S* (2) method of drying, (3) degree of moisture, and (4) temperature at

time of loading. The following materials are subject to spontaneousignition especially when damp, greasy, oily or mixed with varnish -

artifical wool, automobile brakeband lining, batting dross,canvas, feathers, felt, filter press cloth, hair, mungo, shoddy, twist,waterproofed cloth, waste wool, wool pickings, wool waste.

I

21424

NSWC/WOL/TR 75-159

Conclusions (Ref: 1-21,43-49,11.1,131-136,138-145)

Substances subject to spontaneous combustion can be divided intothe following categories:

(a) Substances which are noncombustible but can causeignition as a result of spontaneous heating (calcium oxide, alkali,alkali earth oxides, etc.).

(b) Substances with low ignition temperature whose oxidationis allowed to proceed freely. The ratio of the surface exposed tothe mass being heated is so great that heat is generated by oxidationmore rapidly than it can be dissipated, and the temperature riseslocally until the ignition point is reached. Pyrophoric characterin general depends upon the nature and chemical reactivity of thematerial and varies with the amount of exposed surface and thephysical condition of that surface (finely divided metals, hydridesof phosphorus, white phosphorus, etc.).

(c) Combustible aubstances which ignite spon~taneously as aresult of slow oxidation -- vegetable and animal fats and oilscontaining glycerides of unsaturated fatty oils that abaorb oxygeninto double bonds producing heat, coal, wood charcoal, woodproducts, etc.

(d) Materials where biological processes cause spontaneousignition as a result of the metabolism of living organisms sub-sequently furthered by the absorption of oxygen - hay, grains, fishmeal, sugar, peat, and other agricultural products.

(e) Materials which teact with water, forming flammable orexplosive products (active metals, hydrides, carbides, phosphides,etc).

Although the causes of spontaneous combustion are few, theconditions under which these factors may operate to create adaugercus situation are many and varied. In some cases more thanone factor nmay be operative (oxidative and/or biological) and onemay initiate conditions favorable to the functioning of another.

Except for air-hazardous (pyrophoric) and water-hazardousmaterials, the tendency of susceptible materials to heat isgenerally increased by elevated temperatures and by the insulatingeffect of the material alone or by surrounding conditions in transitor in storage. Spontaneous heating does progress in various materialswithout hazardous effects if the conditions are such that thegenerated heat is dissipated at a rate that prevents the materialfror reaching its critical temperature. This temperature varies fordifferent materials but once reached, combustion can occur.Ventilat 4.on is thus an important factor in preventing many instancesof poten'.ial spontaneous ignition, although a complete lack ofventilation is also a certain deterrent against combustion in cases

25

NSWC/WOL/TR 75-159

where fixed oxygen is not present in the material. This fact maybe utilized where small quantities of material make practical theuse of air tight containers or compartments.

Temperature measurements in the interior of a mass of materialwill give an indication of the progress of spontaneous heating.These temperatures, taken at various locations within the materialwould detect localized focal points where spontaneous heating couldbe cccurring.

In the shipping and storage of agricultural products, the useof moisture control and biocides could reduce the hazard of spon-taneous combustion and the self-heating of these materials.

•226

?I

IiI

26

NSWC/WO /TR 75-159

REFERENCES

1. • P. Rothbaum, Journal of Applied Chemistry, 13, 291, 1963.

2. H. P. Rothbaum, Ibid., 14, 165, 1964.

3. H. P. Rothbaum, Ibid., 7, 291, 1964.

I• 4. R. E. Carlyle and A. G. Norman, Journal of Bacteriology, 4,

669, 1941.

5. T. Gibson et al., Journal General Microbiology, 19, 122, 1958.

6. M. Milner et al., Cereal Chemistry, 24, 507, 1947.

7. 0. F. Edwards and L. F. Rettger, Journal of Bacteriology, 34,489, 1937.

8. J. B. Firth and R. E. Stuckey, Nature, 159, 624, 1947.

[ 9. C. A. Broone, Science, 77. 223, 1933.

10. A. H. Nuckolls, Underwriters Laboratories Inc., ResearchBulletin, 2,3, 1938.

11. W. W. Moore, National Fire Prevention Association Quarterly,6,188, 1912.

*112. N. D. Mitchell, Ibid., 45, 165, 1951. sfr

i:13. A. K. Leont'ev and V. V. Pomerantsev transulated for Zhur.•

_Priklad. Khim., 33, 940, 1960.

14. N. N. Semenov, "Chemical Kinetics and Reactivity", Vol. 2,Pergamon Press. London, 1958.

15. D. A. Frank-Kamenetskii, "Diffusion and Heat Transfer inChemical Kinetics," 2nd ed., Plenum Press, New York, 1969.

16. P. H. Thomas, Trans. Faraday Soc., 54, 60, 1958ý

17. P. H. Thomas, "Ignition, Heat Release and Non-combustibilityof Materials," ASTM STP 502, Phila. Pa., 56, 1972.

18. D. E. McDaniel, Ibid., 24, 1972.

i 19. I. K. Walker, W. J. Harrison and C. N. Hooker, N.Z.J. Sci.,8, 319, 1965.

20. I. K. Walker, W. J. Harrison and A. J. Read, Ibid., 10,32,1967.

21. I. K. Walker and A. J. Read, Ibid., 12, 302, 1969.

27

L : .... ... .. . . . . .. . .... . .-.. . . .. .. ..... . . •x.., . • • • , ,.m . • • =• • •••• •, • • • • | '

NSWC/WOL/TR 75-159

22. I. K. Walker, Ibid., 4, 309, 1961.

23. E. K. Rideal and A. J. B. Robertson, 3rd Symposium on Combustion,Flame and Explosion Phenomena, Williams & Wilkins Co.,

I, - Balto., Md., P. 536, 1949.

24. J. L. C. Van Geel, Ind. Eng. Chem. (ind.) 58, 25, 1966.

25. N. J. Thompson, Ind. and Eng. Chem., 19, 394, 1927.k

26. F. D. Snell and C. L. Hilton eds., Encyclopedia of IndustrialChemical Analysis, Interscience, New York.

27. ASTM D 2155-63T, Method of Test for Autoignition Temperatureof Petrol1eum Products (Tentative), American Society for Testingand Materials, Philadelphia, Pa., 1965.

28. S. S. Penner and B. P. Mullins, "Explosions, Detonation,Flammability, and Ignition," Pergamon Press, London, 1959.

29. N. P. Setchkin, Journal of Research - NBS, Research Paper 2516,[ l 53, 49, 1954.

30. P. C. Bowes, Journal of Applied Chemistry, 4, 140, 1954.[ 31. J. T. Geoghegan and E. H. Sheers, Rubber Age, 102, 63, 1970.

32. J. T. Geoghegan and E. H. Sheers, J. Chem. Educ., 43, A-429, 1968.

33. W. Helmore, "Science of Petroleum," Vol. 4, Oxford Press, p. 29701938.

34. J. M. Kutchta and A. F. Smith, Bureau of Mines Report ofInvestigation No. 7593, 1972.

35. Department of Transportation No. TSA-20-72-2, by C. M. Mason andV. C. Cooper, Bureau of Mines (Pittsburgh Mining and SafetyResearch Center Report No. 4160, 10 March 1972).

36. W. J. Scott, Advances in Food Research, 7, 83, 1957.

37. H. P. Rothbaum, Journal of Bacteriology, 81, 165. 1961.

4 38. I. K. Walker and W. J. Harrison, N.Z.J. agric. Res., 3, 861, 1960.

39. R. E. Du Four and C. C. Clogston, Underwriters LaboratoriesResearch Bulletin No. 47, 5, 1953.

40. J. P. Foster, International Sugar Journal, 28, 603, 1926.

41. A. Schone, Deut. Zuckerind, 36, 608, 1926.

42. M. I. Goldin, Bull. State Agr. Microbiol. (USSR), 8, 155, 1936.

28 !}

NSWC/WOL/TR 75-159

43. M. K. Valdhuis, L. M. Christensen and E. I. Fulmer, Ind. Eng.

Chem., 28, 430, 1936.

44. R. 0. E. Davis and J. 0. Hardesty, Ind. Eng. Chem., 37, 59, 1945.

45. J. 0. Hardesty and R. 0. E. Davis, Ibid., 38, 1298, 1945.

46. Anon., Textil-Rendschau, 12, 273, 1957.

47. 1. K. Walker and H. M. Williamson, J. Appl. Chem. (London),7, 468, 1957.

48. I. K. Walker and W. J. Harrison, N.Z.J. Sci., 4, 26, 1961.

49. I. K. Walker and W. J. Harrison, Ibid., 8, 106, 1965.

50. W. D. Felix and H. Eyring, J. Text. Res., 33, 465, 1963.

51. I. K. Walker, W. J. Harrison and G. F. Patterson, N.Z.J. Sci.,11, 380, 1968.

52. A. J. Read, W. J. larrison and I. K. Walker, Ibid., 10, 964,1967.

53. M. S. Carrie, I. K. Walker and W. J. Harrison, J. Appl. Chem.,9, 608, 1959.

54. F. M. Fowkes et al., J. Agr. Food Chem., 0, 203, 1960.

55. I. K. Walker and W. J. Harrison, N. Z. J. agric Res. 3, 861,1960.

56. M. Milner and W. F. Geddes, Cereal Chem., 23, 449, 1946.

57. D. E. H. Frear, "Agricvl-urrl Chemistry," Vol. 2, D. vanNostrandCo., New York, 1951.

58. N. J. Thompson, Oil and 2at Industries, Nov., 317, 1928.

59. B. V. Ettling and M. F. Adams, Fire Technology, 7, 225, 1972.

60. P. S. Hess and G. A. O'Hare, Ind. Eng. Chem., 42, 1424, 1950.

61. M. B. Cunningham, Tappi, 44, 194A, 1961.

62. F. L. Schmidt, Ibid., 52, 1700, 1969.

63. E. L. Springer and G. J. Hajny, Ibid., 53, 85, 1970.

64. G. H. Hajny, Ibid., 49, 97A, 1966.

65. C. W. Rothrock Jr., et al., Ibid., 44, 65, 1961.

29

NSWC/WOL/TR 75-159

66. J. K. Shields and H. H. Unligil, Pulp Paper Mag. Can., 69, 62,

1968.

67. G. H. Hajny et al., Tappi 50, 92, 1967.

68. E. Bjorkman and G. E. Haeger, Tappi, 46, 757, 1963.

69. J. C. McKee and J. W. Daniel, Ibid., 49, 47A, 1966.

70. W. C. Feist et al., Ibid., 56, 148, 1973.

71. R. M. Lindgren and W. E. Eslyn, Ibid., 44, 419, 1961.

72. T. P. Crane, Jr., and D. L. Fassnacht, Tappi, 43, 188A, 1960.

73. H. Greaves, Tappi, 54, 1128, 1971.

74. H. Greaves, Wood Sci. Technol., 5, 6, 1971.

75. W. E. Eslyn, Tappi, 56, 152, 1973.

76. S. La Vaun Merrill Jr., Fuel, 52, 61, 1973.

7 D. L. Carpenter and G. D. Sergeant, Fuel (London), 45, 429, 1966.

78. C. S. Finney and T. S. Spicer, Pyrodynamics, 1, 231, 1964.

79. D. W. Van Krevelen, "Coal", Elsevier Publ. Co., Amsterdam, 1961.

80. K. K. Bhattacharyya, Fuel, 51, 214, 1972.

81. A. K. Bhattacharyya, J. Mines Metals Fuels, 18, 5, 1970.

82. K. K. Bhattacharyya, Fuel (London), 50, 367, 1971.

83. R- L. Bond et al., Fuel (London), 29, 83, 1950.

84. R. E. Jones and D. T. A. Townend, 3rd Symposium on Kinetics andMechanism of Combustion Reaction, p. 459, 1949.

85. M. Gilney, Canadian Mining and Metallurgical Bulletin, 64, 1381971.

86. W. Francis and R. V. Wheller, J. Chem. Soc., 2558, 1967.

87. M. Giney and D. J. Hodges, Chem. and Ind., 42, 1429, 1968.

88. A. Cameron and J. D. McDowall, J. Appl. Chem. Biotechnol., 22,1007, 1972.

30

NSWC/WOL/TR 75-159

89. P. C. Bowes and A. Cameron, J. Appl. Chem. Biotechnol., 21,244, 1971.

90. N. Boden et al., J. Appl. Chem. (London), 12, 145, 1962.

91. K. Akita, Rep. Fire Res. Inst. (Japan), 9, 1, 1959.

92. P. H. Thomas and P. C. Bowes, J. Appl. Physics (British), 12,222, 1961.

93. T. Kinbara and A. Kawasaki, Bull. Fire Prevent. Soc., (Japan),

16, 9, 1967.

I . 94. P. Gray and P. R. Lee, in Oxidation and Combustion Reviews,Vol. 2, Elsevier Publ. Co., London, 1967.

95. N. Berkowitz and J. G. Speight, Can. Min. Met. Bull., 66,109, 1973.

96. G. E. Mapsone, Chem. and Ind. (London), 658, 1954.

97. N. Berkowitz and H. G. Schein, Fuel, 30, 94, 1951.

98. F. E. Littman and F. M. Church, AEC Research and DevelopmentReport - "A Study cf the Spontaneous Ignition of Metals," SRIProject No. SU-2887, Contract No. AT(04-3)-115, Aug 15, 1960.

99. C. 0. Nelson and D. B. Nelson, Sodium Air Reaction ExperimentsKAPL-639, Jan 1952.

100. B. Kopelman and V. B. Compton, Metal Progress, 63, 77, 1953.

101. E. J. Badin, 3rd Symposium on Combustion, Flame and ExplosionPhenomena, Williams and Wilkins Co., Baito., Md., 1949.

102. J. E. Knapp et al., Ind. and Eng. Chem., 49, 874, 1957.

103. J. Marsel and L. Kramer, 7th Symposium (International) onCombustion, the Combustion Institute, Butterworth ScientificPublications, 1959.

104. W. R. Wilcox, Dangerous Materials - A Compatibility Study,General Electric Co., AD-766-947, St. Louis, MO, Feb 1973.

105. National Fire Prevention Association, National Fire Codes -

Combustible Solids, Dusts and Explosives, Vol. 3, 492, 1964-65.

106. National Fire Prevention Association, Ibid., Vol. 3, 321, 1968-69.

107. J. R. Gibson and J. D. Weber, Handbook of Selected Propertiesof Air and Water Reactive Materials, U.S. Naval AmmunitionDepot, Crane, IN RDTR No. 144, March 1969.

31

NSWC/WOL/TR 75-159

108. Bureau of Fire Previntion - City of Los Angeles, DangerousChemicals Code, Parker and Co., Los Angeles, CA, 1951.

109 J. Aeby, "Dengerous Goods and Others", Lloyd Anversois, Antwerp* 4th ed., 1955.

110. A. Webster, Chem. and Ind. (London), 5, 502, 1958.

111. United Nations, "Transport of Dangerous Goods (1970), Vol. 1"ST,'ECA/81/Rev. 2, E/CN.2/Conf. 5/10/Rev. 2, 1 Nov 1970.

112. European Agreement Concerning the International Carriage ofDangerous Goods by Road (ADR): Annex A - Provisions ConcerningDangerous Substances and Articles, Her Majesty's StationeryOffice, London, 1970.

f 113. International Regulations Concerning the Carriage of DangerousT Goods by Rail (RID), Her Majesty's Stationery Office, London, 1973.

114. H. Zeiss, "Organometallic Chemistry," Reinhold Publ. Co.,New York, 1960.

115. G. E. Coates, "Organo-Metallic Compounds," John Wiley and SonsInc, New York, 1956.

116. D. T. Hurd, "An Introduction to the Chemistry of Hydrides,"John Wiley and Sons Inc., New York, 1952.

117. H. C. Kaufman, "Handbook of Organometallic Compounds,"D. Van Nostrand Co., Inc., New York 1961.

118. National Fire Prevention Association, National Fire Codes,Vol. 3, Boston, MA, 1965-66.

119. E. G. Rochow, D. T. Hurd and R. N. Lewis, "The Chemistry ofOrganometallic Compounds," John Wiley and Sons Inc., Now York,1957.

120. N. I. Sax, "Dangerous Properties of Industrial Materials,"Reinhold Publ. Corp., New York, 1963.

S121. F. D. Snell and C. T. Snell, "Dictionary of Commercial Chemicals,"D. Van Nostrand Co. Inc., New York, 1962.

122. R. A. Zingaro and R. E. McGlothlin, J. Chem. and Eng. Data,8, 227, 1963.

123. J. R. Van Wazer, "Phosphorus and its Compounds," Vol. 1,Interscience Publ. Inc., New York, 1958.

124. W. Ripley, RDTN, No. 32, U.S. Naval Ammunition Depot, Crane, IN,Oct. 28, 1966.

32

NSWC/WOL/TR 75-159

125. National Fire Prevention Association, Fire Prevention Guideon Hazardous Materials, Boston, MA, 1966.

126. Metal Organic Compounds, Advances in Chemistry Series No. 23,American Chemical Soc., Wash. D. C., 1957.

127. P. G. Stechler et al., eds., "Merck Index of Chemicals andDrugs," Merck and Co., Rahway, New Jersey, 1960.

128. F. Paulden, Chemical Products, 10, 67, 1947.

129. F. Paulden, Chemical Products, 11, 26, 1948.

130. M. S. Silverstein et al., Ind. and Eng. Chem., 40, 301, 1948.

131. J. H. McGuire, Fire Technology, 5, 237, 1969.

132. H. H. Brown and N. J. Thompson, NFPA Quarterly, 25, 255, 1932.

133. C. A. Clifford, G. Hampel, and G. Hawley eds., Encyclopedia ofChemistry, Van Nostrand-Reinhold Co., 3rd ed., p. 291, 1973.

134. Thorpes Dictionary of Applied Chemistry, 4th ed., Longmanand Green and Co., New York, 1954.

135. V. Virtala, Valtion Teknillinene Tutkimuslaitoksen - S•im.aryTranslation, Julkaisuja, Helsinki, 14, 57, 1949.

136. A. S. Minton, Trans. Inst. Marine Engrs, 75, Suppl. i, 1963.

137. W. H. Shearon Jr., Chem. and Eng News, 29, 17, 1951.

138. Guide to Precautionary Labeling of Hazardous Chemicals,Manufacturing Chemists Assoc., inc., 5th ed., Wash. D.C., 1961.

139. H. Fawcett and W. S. Wood, "Safety and Accident Prevention inChemical Operation," Interscience, New York, 1965.

140. J. F. ;4obis, Ind. and Eng. Chem., 49, 44A, 1957.

141. A. K. Leont'ev in Oxidation and Combustion Reviews, Vol. 2,Elsevier Publ. Co., London, 1967.

142. J. T. Garrett, Safety Maintenance and Production, 112, 26, 1956..

143. R. D. Minteer, Ind. Eng. Chem., 47, 1202, 1955.

144. J. B. Firth, Proc. 3rd Conf. Chem. Wks. Safety, 89, 1950.

145. C. C. Concannon, Chem. Eng. News, 29, 3612, 1951.

33

NSWC/WOL/TR 75-159

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