TNT Trinotrotoluenes, Mono , and Dinitrotoluenes pdf

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r r i

r R r N I T E O T O L U E N E S A N D

M O N O - A N D D I N I T B O T O L U E N E S

THEIR MANUFACTURE

AND PROPERTIES

BY

G . C A R L T O N S M I T H , B . S . Instructor in General Chemistry, School of Applied Science,

Carnegie Institute of Technology, Pittsburgh, Pa,

L O N D O N

C O N S T A B L E A N D C O M P A N Y , L I M I T E D 10 O R A N G E S T . , L E I C E S T E R S Q . , W . C .

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A C K N O W L E D G M E N T

T H E writer wishes t o t h a n k all those who h a v e so kindly aided h i m in t h e p r e p a r a t i o n of this book.

H e is especially grateful for t h e v a l u e d c o m m e n t s a n d criticisms offered b y t h e m e m b e r s of t h e Staff of t h e D e p a r t m e n t of Chemical Engineering, Carnegie I n s t i t u t e of Technology; for t h e facts which form t h e basis of C h a p t e r X , b y D r . S a m u e l H a y t h o r n of t h e Singer Memorial L a b o r a t o r y , Allegheny General H o s -p i t a l ; a n d for d a t a on T N T m a n u f a c t u r e b y M r . R o b e r t M . Crawford of t h e Grasselli Powder C o .

T h e Chemical a n d I n d u s t r i a l J o u r n a l s h a v e been consulted freely, and m u c h v a l u a b l e m a t e r i a l h a s been extracted therefrom.

Department of Chemical Engineering, Carnegie Institute of Technology,

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CHAPTER I

PAGE

INTKODUCTION 1

CHAPTER II

HISTORICAL 6

CHAPTER III

THE THEORY OF THE NITRATION OF TOLUENE 20

CHAPTER IV

THE MANUFACTURE OF TNT 29

CHAPTER V

THE PURIFICATION OF TNT 52

CHAPTER VI

INSPECTION AND TESTING OF TNT 61

CHAPTER VII

PROPERTIES OF THE TRINITROTOLUENES 77

CHAPTER VIII

PROPERTIES OF THE MONO- AND DINITROTOLUENES 95

CHAPTER IX

ACCIDENTS IN TNT PLANTS 106

CHAPTER X

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T R I N I T R O T O L U E N E

C H A P T E R I

I N T R O D U C T I O N

T H E almost universal a d o p t i o n of trinitrotoluene as t h e m o s t efficient explosive i n m o d e r n warfare; t h e development a n d refinement of its manufacture, a n d t h e interesting c h e m i s t r y of its compounds, as well as those of t h e lower nitro-derivatives of toluene h a s p r o m p t e d quite extensive research as to their composition, s t r u c t u r e , m a n u f a c t u r e , properties a n d uses. T h e fact t h a t t h e results of these researches h a v e been v a r i e d ; often q u i t e c o n t r a d i c t o r y ; some-w h a t disconnected a n d expressed some-w i t h some confusion of t e r m s would seem t o w a r r a n t t h e publication of this little volume in which a n a t t e m p t is m a d e t o gather together a n d correlate all accessible information on t h e subject, b o t h theoretical a n d p r a c t i c a l .

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use in specifications, etc., t h e y have spreatf tjeyond t h e territory in which t h e y originated. Little wonder is caused, therefore, t h a t t h e uninitiated should confuse t h e several n a m e s now in vogue for trinitrotoluene, a n d t h a t he should t h i n k " T N T " t o be one substance, " t r o t y l " t o b e another, a n d so on. T h e entire list of contractions a n d designations is m u c h too l e n g t h y t o give in its entirety, b u t t h e more familiar ones a r e these:

" T N T " ; t h e American contraction, a n d t h e one usually used for trinitrotoluene in this c o u n t r y .

" Trotyl " ; this t e r m is of English origin, a n d is used almost exclusively i n English specifications a n d literature.

" Tolite " ; t h e F r e n c h abbreviation. " T r i l i t e " ; Spanish.

" F u l l p u l v e r - 0 2 " or simply " Fp-O2 " is used b y t h e Germans t o denote trinitrotoluene. T h i s is, of course, neither a contraction nor a n abbreviation of t h e name itself, b u t denotes merely a certain explosive in accordance w i t h t h e G e r m a n system of classifica-tion.

Some other t e r m s a r e " Trinol," " t r i t o l , " " t r i -tolo " and " coal t a r s a l t , " this last being t h e newest designation for trinitrotoluene. B y comparing t h e above terms w i t h t h e full word, t h e relation of m o s t of t h e m is easily seen.

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INTRODUCTION 3

B y t r e a t i n g toluene w i t h n i t r i c acid, three nitro-groups a t t a c h themselves t o t h e molecule in this m a n n e r :

C H3 C H3

O 2 N / N N O 2

+ 3 H N 03- > +3H2O.

N O2

T h i s p a r t i c u l a r t r i n i t r o t o l u e n e is one of t h e six isomeric c o m p o u n d s of t h a t n a m e , and is t h e one formed b y t h e commercial n i t r a t i o n of toluene. Chem-ically it is t h e a, 1 - 2 - 4 - 6 , or " s y m m e t r i c a l " tri-nitrotoluene.

Trinitrotoluene belongs t o t h e shattering class of explosives k n o w n as t h e " b r i s a n t s . " T h e members of t h i s class possess great force, a n d upon exploding, s h a t t e r t h e containing shell i n t o small pieces, t h u s doing more d a m a g e p e r shell.

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On the other hand, trinitrotoluene is.npt quite as powerful as picric acid, but its insensibility to shock, together with the advantages cited above, have resulted in its almost totally replacing the latter in warfare. T h e first nation t o use trinitrotoluene in shells was the Germans, who adopted it in 1904.

The great insensibility of trinitrotoluene as com-pared to that of picric acid, is shown in the following table of minimum charges necessary for the detona-tion of both explosives:

Detonator. Mercury fulminate Cadmium fulminate Silver fulminate Mercurous azide Lead azide Silver azide Cadmium azide TNT. Gram. .36 .11 .095 .145 .09 .07 .04 Picric Acid. Gram. .30 .05 .05 .075 .025 .035 .02

Aside from its use individually as an explosive, trinitrotoluene is often mixed with other ingredients. The most important of these blends, together with their analyses, are:

" Thunderite"; T N T , 4 per cent; ammonium nitrate, 92 per cent; flour, 4 per cent.

" P e r m o n i t e " ; T N T , 10 per cent; ammonium nitrate, 42.5 per cent; potassium chlorate, 32.5 per cent; starch, 12 per cent; wood meal, 3 per cent.

" Aluminium e x p l o s i v e " ; T N T , 31 per cent; ammonium nitrate, 44.9 per cent; aluminium wool, 24.1 per cent.

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INTRODUCTION 5

" M a g a n t e " ; T N T , 30 p e r c e n t ; lead n i t r a t e , 70 p e r cent. „

" D o n a r i t e " ; T N T , 12 p e r c e n t ; col.cot. 0.2 p e r c e n t ; a m m o n i u m n i t r a t e , 80 p e r c e n t ; flour, 4 p e r c e n t ; nitroglycerine, 3.8 p e r cent.

Dinitrotoluene is also u s e d in conjunction w i t h o t h e r materials as a n explosive. One such mixture is " C h e d d i t e - 0 2 . " T h e analysis of t h e m i x t u r e i s : D N T , 15 per cent; p o t a s s i u m chlorate, 79 per c e n t ; m o n o n i t r o n a p h t h a l e n e , 1 p e r c e n t ; castor oil, 5 p e r cent.

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HISTORICAL

SOME doubt exists as t o whom t h e honor of t h e dis-covery of toluene is due. D r . W. Wilson in a n article dated 1850, (1) gives t h e credit of t h e discovery t o Deville, a French chemist, who obtained from b a l s a m of tolu a compound to which he ascribed t h e n a m e

" benzoen." F r o m t h e above article, Deville

evi-dently did not analyze t h e " benzoen " b u t arbitrarily assigned to it the formula C u H i e .

Beilstein and Kuhlberg, in their " E l e v e n t h T r e a -tise on Isomers of t h e Toluene S e r i e s / ' (2) give t h e honor to Pelletier and Walters, also F r e n c h chemists, who obtained an oil from t h e distillation of pine resin, a n d from which oil they separated a liquid which t h e y called " retinaptha." Their description of this liquid is this: " I t is a very clear liquid, . . . boiling a t 108° C , and it is not completely solidified a t —20°. T h e results of three analyses indicate t h e formula C7H8." (This is just half the molecular formula given b y Deville to his substance.) " One could also give t h e formula C u H i e , but there is no definite ground for such a statement. I n fact, t h e vapor density is 3.23— t h e vapor density corresponding t o t h e formula C7H8 would be 3.226."

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HISTORICAL 7

formula (supposedly) C14H16 h a d been isolated, and t h a t , b y determining t h e v a p o r density, they h a d proved it t o be just half this molecular weight, or C7H8. On t h e other h a n d , there is no reason why—if t h e y did know of t h e previous discovery of this same substance — t h e y should give it a new n a m e . T h e dates on which t h e above-mentioned m e n published their article seems to point t o Pelletier a n d Walters as t h e dis-coverers—their work was completed about 1838, while Deville's work was published somewhere about 1841. Of course, there is t h e possibility t h a t Deville completed his work some years before his results were published.

I n 1843, Berzelius technically accorded the discovery of toluene t o Deville b y suggesting t h e name " toluol " or " toluene " for the compound, (3) the n a m e being derived from " oil of t o l u . "

Some of t h e scientists of t h a t period (probably friends of Pelletier a n d W a l t e r s ) , did not approve of Berzelius7 choice of n a m e for this substance, and

two of these, M u s p r a t t a n d Hoffman, in a research paper d a t e d 1845, t a k e occasion to r e m a r k : (4) " Ber-zelius h a s proposed for this compound the n a m e l

tol-uol ' or ' t o l u e n e / n a m e s which are not very well chosen, b u t which we shall r e t a i n in the following dis-cussion."

tc

T h e " r e t i n a p t h a " of Pelletier a n d Walters and the benzoen " of Deville were proved t o be the same sub-stance b y the preparation of t h e nitro-derivatives, and b y comparing t h e constants of those, and possibly the acid nitro-derivatives a n d corresponding toluidins.

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Wai-ter's work, isolated toluene from " Dragon's blood." (5) N o further reference, and consequently no identifica-tion of this substance, could be found. Glenard a n d B o u d a l t gave the name " dracyl " to the substance t h e y isolated. Following t h e methods of their predecessors t h e y proved the identity of dracyl a n d toluene.

Still another man, Cahours, during the years 1 8 4 7 -48 isolated a substance from crude wood alcohol b y treating t h e alcohol with sulphuric acid. H e called this substance " t o l u e n / ' which is so near " toluene " t h a t naturally it would be supposed t o b e t h e same. Cahours demonstrated, however, t h a t t h e formula of " toluen " was C u H s , which gives rise t o a d o u b t as to whether his product was really identical with tol-uene. An abstract, dated 1849, reads t h u s : (6) " Cahours has separated from crude wood alcohol different oily hydrocarbons, some already k n o w n ; some new. Toluen C14H8 is identical with t h e toluene of Deville. I t distills between 108 a n d 112° C. Cahours found t h e vapor density to be 3.27. T h r o u g h t r e a t m e n t with nitric acid he obtained mono- a n d dinitrotoluene, and from these, b y reduction w i t h ammonium sulphide, t h e corresponding toluidin a n d nitrotoluidin."

I t is rather difficult to understand w h y Cahours insisted on the formula C14H8 after having determined a vapor density of 3.27, which so closely checked Pelletier and Walter's determination.

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HISTORICAL 9

toluene \^ill be cited, however, because of its scientific interest. I n 1846, two G e r m a n chemists, Tollens a n d Fittig, prepared toluene synthetically from m e t h y l iodide a n d brombenzene. (8) This method was a modification of Wurz7 synthesis of the aliphatic h y d r o

carbons, a n d it is interesting because the primary p r o d uct of t h e now commercially valuable " Fittig's s y n -thesis " was toluene, t h e basis of t h e greatest explosive of modern times.

T h e earliest reference t o b e found concerning t h e purification of coal t a r toluene is contained in Wilson's paper, (9) wherein he s t a t e s : " " T h e best m e t h o d of obtaining p u r e toluene consists in collecting t h e p a r t which passes over between 100 and 120° C. and t r e a t -ing this with one-half its weight of concentrated sul-phuric acid. I h a v e not determined which substances are removed in this process; t h e fact remains, however, t h a t a constant boiling-point is obtained more easily t h r o u g h t h e use of sulphuric acid t h a n without. T h e boiling-point of p u r e toluene was found to be 110° C. . . . U n d e r all conditions a series of protracted dis-tillations is necessary t o obtain this object."

As is seen from this statement, Wilson followed t h e same m e t h o d of procedure as is followed to-day in order t o effect t h e removal of t h e olefines from t h e crude toluene. M o d e r n plants, equipped with t h e latest t y p e of fractionating stills, with their compli-c a t e d compli-columns, refluxes a n d fracompli-ctional compli-condensers are fortunately n o t p u t to t h e same trouble in t h e p u r i -fication of toluene as was Wilson.

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tol-uene w a s identified b y t h e several chemist^. Deville p r e p a r e d t h e mononitrotoluene and also t h e sulphonate of toluene. T h e nitrocompound he called " p r o t o n i -trobenzoen," a n d describes it in this m a n n e r : " I t tastes like b i t t e r almonds; smells suffocating a t first t h e n penetrating. I t s specific gravity is 1.18 a t 16°. I t boils a t 225°." T h e same chemist found the v a p o r density t o be 4.95. T h e vapor density as calculated b y h i m would be 7.87, basing t h e calculation on his formula of C u H i 6 for toluene. (10)

Berzelius, in a research paper published in 1843, gives i n detail t h e p r e p a r a t i o n of nitrotoluene. (11) T h e results of a series of researches t o prove its con-stitution are mentioned also. Berzelius was misled b y his results., as was Deville. His final conclusion states, " Nitrotoluene can b e considered as a n i t r i d e of toluid oxide, C i 4 H i 4 0 = N . " T h e chemical proper-ties of nitrotoluene were studied a t length b y Berzelius, b u t he evidently arrived a t no definite conclusion re-garding these properties.

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Comment-HISTORICAL 11

ing on tjjris question, Beilstein a n d Kuhlberg (12) explain t h e decomposition of nitrotoluene as being due to t h e p r o b a b l e content of higher nitro-derivatives of toluene. T h i s we now know t o b e t h e t r u t h , and t h e firms who are purifying their nitrotoluene b y distilla-tion are v e r y careful t o remove all t h e higher nitro-compounds before a t t e m p t i n g t h e distillation.

A b o u t this time, another chemist entered the field of t h e nitro-compounds. T h i s m a n w a s Jaworsky. H e s t a r t e d o u t his work b y preparing nitrotoluene, which h e claimed to b e a solid, a n d n o t a liquid as Deville, Wilson, a n d others h a d t h o u g h t it to be. (13) J a w o r s k y represents a b o u t t h e best t y p e of p u r e indus-trial chemist t o b e found in this period of time. His work on nitrotoluene h a d a great effect on the indus-tries; so m u c h so, t h a t a t t h e Paris Exposition of 1867 there was exhibited a great q u a n t i t y of beautifully crystallized nitrotoluene. W h e t h e r this consisted of the p u r e solid isomer of nitrotoluene or whether it was a m i x t u r e of one or more nitrotoluenes a n d dini-trotoluenes, is n o t known. Jaworsky w a s also t h e first t o produce toluidin—the homologue of aniline— b y t h e reduction of nitrotoluene w i t h t i n a n d h y d r o -chloric acid. T h e immediate industrial result of J a w o r s k y ' s work was t h a t the use of nitrotoluene as a dyestuff base was firmly established.

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nitro-toluene is nothing else t h a n a mixture of n^rotolu< a n d nitrobenzene."

Summarizing t h e work of these earlier i n v e s t i tors of t h e nitrotoluenes, there is one fact t h a t s t a i out very clearly t h r o u g h o u t all their w o r k — t h e y 1 n o thought of t h e possible isomerism of n i t r o t o l u e T h e results obtained b y all t h e various work d o n e these chemists was finally interpreted b y K e k u l e meaning t h a t nitrotoluene was a solid, a n d t h a t ' liquid obtained b y Deville a n d others was a liqi only because of t h e admixture of nitrobenzene.

This cloud began t o disappear w i t h t h e w o r k Rosenstill, who was t h e first to suggest t h e possibil of t h e existence of nitrotoluene in different fori H i s work was later supplemented b y Beilstein a Kuhlberg, who found in Rosenstill's work t h e h t h a t led t o their isolation of t h e t h r e e isomeric n i t toluenes, and t h e classification a n d n a m i n g of t h compounds. T h e results of Beilstein and K u berg's work was published in 1879, when, for t h e fi time, the true constitutions of t h e nitrotoluenes \ established.

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HISTORICAL 13

to s t a t e tjiat t h e y were led a s t r a y b y s t a t e m e n t s a n d hypotheses which later p r o v e d t o b e w i t h o u t founda-tion. T h e p a r t i c u l a r point t o which I refer is t h e nomenclature used b y Beilstein a n d K u h l b e r g for t h e nitrotoluenes. T h i s m a y a p p e a r a small m a t t e r , b u t when reference is m a d e to t h e publications of these m e n , a n d when these references a r e viewed in t h e light of present d a y accepted facts, their nomenclature is con-fusing. M o r e so, because t h e y m a d e use of t h e t e r m s " o r t h o , " " m e t a , " a n d " p a r a , " which are t h e same a s a r e used today. T h e m e t a a n d ortho isomeric n i t r o -toluenes appear t o b e j u s t reversed from those isomers now regarded as m e t a a n d o r t h o . T h i s view was n o t d u e t o Beilstein a n d K u h l b e r g alone, for a t least one other scientist, V. von Richter, was of t h e same mind. Von Richter states t h u s : (14) " T r i n i t r o t o l u e n e from

meta mononitrotoluene crystallizes in yellow needles

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Ortho Meta Para

These same constants as we have t h e m to-day,

Ortho Meta Para.

Melting-point.

16

54

B^jiling-point.

230-231 222-223 235-236

of t h e nitrotoluenes n a m e d are different:

Melting-point.

-10.5 16 54

Boiling-point.

218-220 230 234

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HISTORICAL 15

After Beilstein a n d K u h l b e r g completed their work on t h e nitrotoluenes, t h e y set a b o u t investigating tol-uene t o discover whether or n o t t h i s substance existed i n isomeric forms, thinking t h e r e b y t o explain t h e isom-erism of t h e toluene derivatives. Their experiments are interesting in t h e extreme, b u t are too lengthy t o discuss in this book. Suffice it t o say t h a t t h e results of their research proved conclusively t h a t toluene existed in b u t one form.

I n considering t h e discovery of dinitrotoluene, w e m u s t again give t h e credit t o Deville. H i s original p a p e r on the general subject of toluene a n d its n i t r a tion derivatives contains t h e s t a t e m e n t t h a t he p r e -pared t h e dinitro-compound, which he called " binitro-benzoen," in direct accordance w i t h t h e scheme of nomenclature h e adopted. Deville gives t h e melting-point of his preparation as 71°. Therefore it is inferred t h a t his " binitrobenzoen " was 1-2-4 dinitrotoluene. (15)

Cahours also prepared a dinitrotoluene, b u t unfor-t u n a unfor-t e l y he did nounfor-t leave a n y d a unfor-t a as unfor-to which of unfor-t h e isomers he obtained.

Beilstein a n d K u h l b e r g p r e p a r e d t w o dinitrotol-uenes, b u t give the melting-point of b u t one of t h e t w o . T h i s was t h e same as t h a t of Deville. T h e work of Beilstein and Kuhlberg seems to h a v e been mostly on t h e mononitro-compounds of toluene, a n d t h e acidic a n d basic compounds of mononitrotoluene.

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obtained; the ortho a n d p a r a . " T h i s s t a t e m e n t is further proof t h a t Beilstein was mistaken in his no-menclature.

The second dinitrotoluene was discovered b y Rosen-still, b u t he was not sure whether it was t h e 1-2-3, t h e 1-2-5, or t h e 1-2-6 compound. D r . C u n e r t h , after much work, identified this dinitrotoluene as t h e 1-2-6 modification.

The 1-3-4 dinitrotoluene was discovered b y Beil-stein, who did this work independently of Kuhlberg in 1873. I t was then t h a t Beilstein gave t h e names to t h e three known dinitrotoluenes. T h e 1-2-4 modi-fication he called t h e a; t h e 1-2-6, t h e (3; a n d t h e 1-3-4, the 7. This nomenclature is n o t strictly adhered to, b y modern chemists, t h e usual m a n n e r of denoting a certain di- or trinitrotoluene being to s t a t e t h e position occupied b y t h e groups.

Lampricht is credited with t h e isolation of t h e next dinitrotoluene. This was t h e 1-2-5 derivative, a n d was discovered b y Lampricht during experiments on the action of fuming nitric acid on toluene.

The isolation of t h e remaining t w o modifications, the 1-2-3 and the 1-3-5 is somewhat in d o u b t . T h e sources of information a t h a n d point t o either Nolting and Witte or t o Bernthsen as t h e discoverers.

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HISTORICAL 17

modification. Peculiarly enough, this was t h e first discovered, v e r y likely because i t is t h e modification present in t h e largest p r o p o r t i o n s in t h e n i t r a t i o n of toluene.

T h e discoverer of t h e s y m m e t r i c a l trinitrotoluene was D r . J. Wilbrand, who, a t t h e t i m e of his discovery, was working a t G o t t i n g e n University. D r . Wil-b r a n d ' s discovery was m a d e in 1862 or 1863. Speaking of his research, which led t o t h e isolation of t h e sym-metrical T N T , D r . W i l b r a n d s a y s : " T h e p r e p a r a t i o n of trinitrotoluene is v e r y easy. Toluene is h e a t e d t o a b o u t boiling t e m p e r a t u r e w i t h a m i x t u r e of fuming nitric a n d sulphuric acids for a d a y . T h e acid mix-t u r e is agimix-tamix-ted wimix-th wamix-ter, a n d mix-t h e residue is crysmix-tal- crystal-lized after washing w i t h w a t e r a n d drying with alcohol. T h e analysis of trinitrotoluene i s :

Carbon... Hydrogen Nitrogen. Oxygen..

Trinitrotoluene crystallizes in white glistening needles, which are, t o all appearances, scarcely differ-e n t from dinitrotoludiffer-endiffer-e. T h i s substancdiffer-e m differ-e l t s a t 82° a n d is easily soluble in h o t alcohol, b u t v e r y slightly in cold. I n ether it is easily soluble. Boiling alkalies react m u c h easier with trinitrotoluene t h a n w i t h dini-trotoluene. F r o m t h e deep r e d alkaline solution, acids precipitate d a r k flocks.'7 (17)

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proved it to be symmetrical. (18) T h e melting-point was found to be 82°, in accordance with D r . W i l b r a n d ' s statement. I n the light of modern research, this melt-ing-point appears too high. T h e correct meltmelt-ing-point is probably 80.6°.

T h e next trinitrotoluene to be isolated was t h e 1-2-3-6 modification. This was discovered b y P a u l H e p p in 1882. (19) H e p p found the melting-point of this trinitrotoluene t o be 112°.

T h e discovery of t h e 1-2-3-6 compound was fol-lowed very shortly b y t h e disooyery of t h e 1 - 2 - 4 - 5 modification b y Beilstein, who isolated b o t h t h e 1-2-3-6 a n d the 1-2-4-5 isomers the same year t h a t H e p p isolated the 1-2-3-6. Beilstein found t h e melting-point of the 1-2-4-5 isomer to be 104° C.

T h e remaining three trinitrotoluenes h a v e been discovered in very recent times. I n 1914, Giua a n d Molinari discovered t h e 1-2-3-5 modification. (20) T h e isolation of this compound was accomplished while the discoverers were working on an industrial problem with the oily substance resulting from the centrifugali-zation of, crude dinitrotoluene. I t will be remembered t h a t Nolting and W i t t e worked with this same s u b -stance in 1885. These latter investigators overlooked this trinitrotoluene a n d also several dinitrotoluenes, since Giua and Molinari found the following constitu-ents in the oil.

Mono-.

1-3 1-4

Di-.

1-2-4 1-2-5 1-2-6 1-3-4

Trinitrotoluenes.

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HISTORICAL 19

Giua a n d Molinari give t h e melting-point of this trinitrotoluene as 79.5°.

T h e next trinitrotoluene t o b e isolated was t h e 1-3-4-5 modification. This was discovered b y Korner a n d C o n t a r d i in 1915. (21) U n d e r w h a t conditions, or from w h a t source this trinitrotoluene was dis-covered is not known, since t h e original reference is not a t h a n d . T h e melting-point given b y t h e dis-coverers is 97.2°.

T h e last trinitrotoluene, a n d t h e last of t h e fifteen possible nucleus-substituted nitro-derivatives of toluene, is supposed to have been discovered b y Coparisow during t h e latter p a r t of t h e y e a r 1915. (22) T h e melting-point of this trinitrotoluene is 137.5°.

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T H E THEORETICAL NITRATION OF T O L U E N E

I N this discussion of t h e theoretical n i t r a t i o n of toluene, I shall m a k e use of the ideal process—the three-stage. If either t h e one- or two-stage processes were substituted, t h e r e would be changes in minor points only, and I t h i n k t h e three-stage illustration will ren-der t h e theory m o r e clear.

T h e reactions of t h e first nitration of toluene are as follows:

First stage:

C6H5CH3 + H N O 3 -> C6H4(CH3) (NO2) + H 2 O .

There is also a possibility t h a t the reaction m a y go forward in two steps, t h e first step being t h e sulpho-nation of the toluene, a n d the second step t h e substitu-tion of nitro-groups for t h e sulphonic groups:

C6H5C H3 +H2SO4 -> C6H4( C H3) (SO3H) + H 2 O

and,

C6H4(CH3) (SO8) + H H N O3- > C6H4(CH3) ( N O a ) + H2S O4.

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THE THEORETICAL NITRATION OF TOLUENE 21

2) +H2SO4

- * C6H3(CH3)(NO2)(SO3H) + H 2 O ,

a n d

C6H3(CH3)(NO2)(SO3H) + H N O 3

T h e third-stage reaction is similar to t h e second s t a g e :

C6H3( C H3) ( N O2)2 + H2S O4

- * C6H2(CH3)(NO2)2(SO3H) + H 2 O ,

a n d

C6H2(CH3)(NO2)2(SO3H) + H N O 3

-> C6H2( C H3) (NO2)3 + H 2 S O 4 .

I n each stage there m a y b e t h e reactions of either previous or later stages t a k i n g place, because of t h e impossibility of absolute control.

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stage has resulted in t h e formation of i s o m e ^ w i t h the groups in such positions t h a t the sulphonic group cannot e n t e r t h e molecule easily, t h e isomer will b e n i t r a t e d only b y very strong nitric acid, or b y using some special m e t h o d of introducing t h e sulphonic group.

This solution to t h e question would seem to indicate t h a t in t h e first-stage nitration the sulphonation does n o t t a k e place, b u t t h a t t h e toluene is n i t r a t e d directly b y t h e use of nitric acid.

Starting with toluene, purified as is considered neces-s a r y for nitrationneces-s, t h e p r i m a r y nitration ineces-s to mono-nitrotoluene. T h e theoretically perfect n i t r a t i o n would proceed in t h i s m a n n e r :

CH3 CH3 CH3 CH3

NO2

T h i s nitration, however, is never accomplished, for t h e mononitrotoluene consists of all three isomeric forms. T h e mononitrotoluene modifications are present in t h e proportion of 38 per cent para, 60 per cent ortho, a n d 2 to 4 per cent m e t a . (1) This result is exactly w h a t would be expected, because with t h e m e t h y l group in position 1, t h e t e n d e n c y of t h e nitro-groups is to enter either position 2 or position 4. This fact holds t r u e even with t h e more generally accepted view t h a t t h e first stage of t h e reaction consists in sulphonating t h e toluene, because t h e sulphonic group behaves a n d orientates j u s t t h e same as the nitro-group, a n d w i t h t h e m e t h y l group in position 1, t h e sulphonic group

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THE THEORETICAL NITRATION OF TOLUENE 23

nitro-group can t h e n easily replace t h e sulphonic group.

T h e formation of t h e small a m o u n t of m e t a n i t r o -toluene is explained t h u s b y H o l l e m a n : (2) " I t is a p p a r e n t t h a t there is a n o p p o s i t i o n between t h e o r t h o a n d p a r a derivatives on one h a n d , a n d t h e m e t a deriv-atives on t h e other. E i t h e r tjhe first two are t h e chief products, or the last. Concerning t h e t e m p e r a t u r e of t h e reaction, it h a s been p r o v e d t h a t t h e q u a n t i t y of t h e byproducts is t h e smaller, t h e lower t h e t e m -p e r a t u r e of n i t r a t i o n . " T h i s s t a t e m e n t of Holleman is based on earlier work b y himself, a n d in a p a p e r he gives this t a b u l a t i o n : (3)

CONSTITUTION OF MIXTURE OF UNITS

Temp, of Nitration. Deg. C. -30 0 30 60 Ortho. Percent. 55.6 56.0 56.9 57.5 Meta. Per Cent. 2.7 3.1 3.2 4.0 Para. Per Cent. 41.7 40.9 39.9 38.9

Considering, then, t h e m i x t u r e of mononitrotoluenes t o consist of, approximately, 38 p e r cent p a r a , 4 per cent m e t a , a n d 58 p e r c e n t o r t h o n i t r o t o l u e n e ; t h e reactions which occur on n i t r a t i n g t o dinitrotoluene will b e investigated.

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another nitro-group,but still ortho or p a r a t o t h e m e t h y l group. Of course, as in t h e first-stage nitration, a small a m o u n t of t h e mononitrotoluene (especially t h e meta) may, under t h e influence of conditions con-cerning which we know nothing, a t t a c h nitro-groups in other t h a n t h e specified positions.

By t h e nitration of m e t a nitrotoluene there is formed mainly t h e 1-3-4 dinitrotoluene. Some small a m o u n t s of 1-2-3 a n d 1-3-6 (or 1-2-5) isomers also result from t h i s nitration. (4) I n each of these cases it m a y b e noticed t h a t t h e t e n d e n c y of t h e nitro-group is t o resist the intruding p r i m e nitro-group, which h a s entered t h e molecule c o n t r a r y to t h e laws governing its action, because t h e second group will enter either ortho or para t o t h e m e t h y l group. These isomeric dinitrotoluenes, other t h a n t h e 124, a n d t h e t r i nitrotoluenes together w i t h some unchanged m o n o -nitrotoluene constitute t h e oil t h a t separates from t h e 1-2-4 dinitrotoluene b y centrifugalizing or cooling a n d filtering. This oil is known in Germany as " Bini-trotropfol." Nolting a n d W i t t e (5) s t a t e t h a t this oil constitutes a b o u t 7 per cent of t h e entire charge. Various chemists have analyzed t h e oil, their analyses being summarized a n d checked b y Nolting a n d W i t t e , who found, in addition t o t h e substances isolated b y t h e others, some m e t a nitrotoluene. According t o Nolting a n d Witte, t h e analysis of this oil shows t h e presence of 1-2-4 a n d 1-2-6 dinitrotoluenes, a n d 1-3 and 1-2 mononitrotoluenes. Giua a n d Molinari (6) discovered some trinitrotoluenes in t h e oil which were evidently overlooked b y their predecessors.

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mix-THE mix-THEORETICAL NITRATION OF TOLUENE 25

t u r e . T h i s s u m m a r y assumes n o separation of t h e binitrotropfol:

MNT.

1-3 1-2

1-4 (possibly)

DNT.

1-2-4 1-2-6 1-2-3 1-3-4 1-2-5 (1-3-6)

TNT.

1-2-3-4 1-2-4-6 (1-3-4-5) 1-2-4-5(1-3-4-6) (all questionable)

T h e a m o u n t of i m p u r i t i e s ; t h a t is, products other t h a n 1-2-4 dinitrotoluene, a m o u n t s t o from 7 t o 8 per cent.

T h e t h i r d stage is m u c h m o r e complicated t h a n either t h e first or t h e second, o n account of having so m a n y things with which to deal. Possibly b y consider-ing t h e action of each c o m p o u n d separately, t h e result will b e m a d e more clear.

MONONITROTOLUENES

1-3 nitrates to 1-3-4 DNT (possibly further nitrates to 1-3-4-5 TNT) (7);

Also 1-2-3 DNT (possibly further nitrates to 1-2-3-4 TNT) (8); Also 1-2-5 DNT (possibly further nitrates to 1-2-4-5 TNT) (8); 1-2 nitrates to 1-2-6 DNT (9) \ (Both possibly further nitrated to

also 1-2-4 DNT (10). 1 1-2-4-6 TNT).

DINITROTOLUENES

1-2-4 nitrates to 1-2-4-6 trinitrotoluene (10); !_2-6 " 1-2-4-6 " (9); 1-2-5 " 1-2-4-5 " (8);

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(The German theory of nitration, advanced by Hepp, JCscales, etc., and the Italian theory, which is supported by Giua, Molinari, Copari-sow, and others; differ at this point. The Germans assert that 1-3-4-5 TNT is formed from 1-3-4 DNT, while the Italian theorists state that this is impossible. The statements given in substantiation of both theories are quoted at the end of this chapter.)

T h e trinitrotoluenes remain unchanged u p o n a t t e m p t s to further n i t r a t e , unless too strong a n i t r a t -ing mixture is used. I n t h i s case t h a y m a y be oxidized to trinitrobenzoic acids or t o tetranitromethane. (11) All of the lower products of nitration must, of necessity, be included in t h e products of t h e thirdstage n i t r a -tion, because a small a m o u n t of a n y or all of these m a y have escaped nitration in all three stages. T h e r e is no reason to suppose t h a t a n y one of t h e nitration reactions m a y have proceeded to completion, with t h e possible exception of t h e nitration of 1-4 mononitrotoluene. This particular nitrotoluene is the most easily n i t r a t e d of the entire number, a n d from all reports, is never found in the finished product. (12)

Summarizing t h e products which may be found in the crude trinitrotoluene, t h e following formidable list appears:

MNT.

1-2 1-3

DNT.

1-2-4 1-2-6 1-2-5 (1-3-6) 1-3-4 1-2-3

TNT.

1-2-4-6 1-2-3-4

1-2-4^6 (1-3-4-6) 1-3-4-5

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THE THEORETICAL NITRATION OF TOLUENE 27 GERMAN MNT. 1-2 1-3 1-4 DNT. r1-2-41 \ 1-2-6 / 11-3-4 I 1-2-3 11-2-5 f1-2-41 11-2-6 i TNT. 1-2-4-6 (1-2-3-4 11-3-4-5 1-2-3-4 1-2-4-5 1-2-4-6 ITALIAN MNT. 1-2 1-3 1-4 DNT. r1-2-41 11-2-6 J r 1-3-4 | 1-2-3 11-3-6 1-2-4 TNT. 1-2-4-6 1-2-3-4 1-2-3-4 1-3-4-5 1-2-4-6

T h e differences in these t w o schemes a r e self evident. T h e Italian t h e o r y is p r o b a b l y correct, in t h a t m u c h more is k n o w n a b o u t t h e behavior of t h e various nitrotoluenes on n i t r a t i o n t h a n was k n o w n when t h e G e r m a n t h e o r y was proposed. I n defense of his theory, H e p p states a s follows:

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' t h e small a m o u n t of substance we had was a mixture.7

T h e t r u t h is, we have succeeded in demonstrating t h a t from a mixture of t h e n i t r a t i o n products of m e t a nitrotoluene at least t w o trinitrotoluenes m a y be isolated. . . . T h e first of these is a difficultly soluble compound having a melting-point of 104° C. T h e second, which I shall designate as the beta compound, is an isomer of t h e first, a n d melts at 112° C . " (13)

Giua's statement is m u c h more brief a n d t o t h e point. H e says:

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CHAPTER IV

THE MANUFACTURE OF TNT

THE complete manufacture of trinitrotoluene

in-volves the several processes of nitration, separation,

washing, crystallization and possibly purification.

The experimental stage has been passed in every one of

these various divisions in the manufacture of this

prod-uct, until the modern plant runs as smoothly as a

well-oiled machine. The apparatus necessary to carry on

any one or all of the steps in the manufacture of TNT

is now well standardized, and many excellent machines

are on the market for accomplishing the end toward

which every manufacturer works—a pure product.

A detailed description of the necessary apparatus will

not be gone into, but a brief outline of the requirements

to be fulfilled by the various machines will be given in

their respective places.

The first step in the manufacture of TNT is the

the nitration. This reaction is carried out in a large

vessel called the nitrator. This nitrator is generally

a cylindrical kettle or tank, built of either an acid-proof

cast metal or of boiler plate. The material of which

the nitrator is built should be thoroughly tested with

the acids of various concentrations met with in the

manufacture of the product. The nitrator must be

well equipped with cooling coils and heating coils so

placed that the temperature of the reacting mixture

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responds instantly to t h e operation of these cgdls. T h e cooling is effected b y t h e circulation of cold water through one set of coils, a n d t h e heating coils m u s t b e supplied with either superheated steam, or steam u n d e r pressure. Some a t t e m p t s h a v e been m a d e to build a nitrating kettle with b u t one set of coils, this set serving for both heating and cooling. So far as I a m aware, there has never been a really efficient nitrator y e t built along the above line. T h e trouble with this type of machine is t h a t when cold water is wanted, it is wanted quickly, and sufficient time to m a n i p u l a t e the several valves necessary on t h e above t y p e of machine is not to be h a d . I n addition t o t h e t e m -perature control coils, t h e n i t r a t o r m u s t be equipped with a good agitating a p p a r a t u s . This agitator is just as necessary as t h e water a n d s t e a m coils, and, through keeping the mixture of toluene a n d acid uni-form, aids in maintaining t h e t e m p e r a t u r e level. T h e manufacture of T N T is essentially a problem in t e m -perature control. After t h e nitration is complete, t h e rest of the process is easy. I n order to check the opera-tor of the nitrating kettle it is well to install a recording thermometer in each unit. This eliminates error, a n d causes the operator to be more careful, because he knows t h a t a mechanical w a t c h is being k e p t on his work.

I have noticed a tendency in quite a number of T N T plants to perform t h e nitration in a r a t h e r slip-shod manner, and on remarking concerning it this reply was made: " Well, its cheaper to use a little less acid in the nitration and purify t h e product afterwards.37

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THE MANUFACTURE OF TNT 31

comparatively safe, it is m a d e primarily to explode. Now, t h e more care t a k e n w i t h t h e manufacture of T N T — t h e less explosions in t h e plant, a n d t h e more explosions out of the p l a n t .

T h e r e are three general processes for t h e nitration of toluene to T N T . These are t h e one-stage, the two-stage, a n d t h e three-stage. All of these are being used a t present in N o r t h America, b u t t h e three-stage seems to h a v e t h e greatest preference. As t h e names imply, t h e process involves either one, t w o or three separate nitrations t o carry t h e toluene to T N T . I n some respects, t h e names " o n e - s t a g e / ' " t w o - s t a g e / ' etc., are misleading, because in every p r e p a r a t i o n of T N T , whether it be b y t h e one-stage, t h e two-stage or t h e three-stage process, there are t h r e e distinct nitrations. W i t h t h e one-stage process these three nitrations are all effected with the one acid m i x t u r e a n d w i t h o u t separation of t h e nitro-derivatives and t h e spent acid until t h e T N T is completed. Similarly, t h e two-stage a n d t h e three-two-stage processes accomplish t h e same thing in either two or t h r e e different steps, each step necessitating separation of t h e spent acid, a n d t h e addition of fresh acid. I t m u s t n o t be supposed, however, t h a t the entire a m o u n t of t h e toluene is converted t o mononitrotoluene before a n y of t h e m o n o is n i t r a t e d t o dinitrotoluene, or t h a t all of t h e m o n o -nitrotoluene is n i t r a t e d to di-nitrotoluene before t h e di- is n i t r a t e d to T N T . T h i s ideal result is not obtained with even t h e three-stage process. N o m a t t e r which of t h e three processes is used, t h e r e will always be m o r e or less impurities existing a t each stage in t h e form of higher or lower nitration p r o d u c t s .

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in the manufacture of T N T m u s t be v e r y p a r e . T h e standard specifications now current in t h e U n i t e d States are as follows:

" T h e first drop m u s t distill not below 108° C. " 95 per cent of t h e entire sample m u s t distill with-in 2°.

" T h e dry point m u s t be below 112° C . "

I n addition, t h e toluene m u s t b e practically free from olefines or members of t h e di-olefine series. T h i s demands t h a t the toluene be washed several times w i t h concentrated sulphuric acid t o remove these com-pounds. T h e laboratory test for olefines consists in agitating some of the toluene with a certain percentage of concentrated sulphuric acid. If olefines are present, the acid layer will acquire a yellow t o red color. T h i s color must not be deeper t h a n whatever shade t h e cer-tain plant has adopted as its s t a n d a r d . T h e com-parison standard colors consist of definite concentra-tions of soluconcentra-tions of potassium dichromate, chromic acid, etc.

T h e presence of olefines is dangerous because these substances form nitro-compounds in t h e nitration proc-ess, and these compounds are r a t h e r unstable. A fire or even an explosion m a y possibly result if t h e toluene is not freed from them. T h e presence of m e m b e r s of the aliphatic or paraffin series is n o t nearly so detri-mental as the presence of t h e olefines. These compounds do not react on nitration, and with t h e t h r e e stage process t h e y m a y be removed after t h e n i t r a -tion to mononitrotoluene.

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THE MANUFACTURE OF TNT 33

is never accomplished. I t is approached most nearly with t h e three-stage process, in which process puri-fication is possible a t each s t e p . I n order to compare t h e t h r e e processes, a n outline of each is given.

NOTE.—The acid mixtures given are approximate only. Each plant has determined just which mixture will give the best results, some of these mixtures varying as much as 10 per cent. A statement of the exact analysis of the mixed acid is therefore impossible.

T h e O n e - s t a g e P r o c e s s . I n t h e one-stage process, b u t one acid m i x t u r e is used. T h i s mixture consists of 75 per cent sulphuric acid, a n d 25 per cent nitric acid. T h e usual charge for t h i s process is in t h e ratio of one p a r t toluene t o twelve p a r t s mixed acid. E a c h kilogram of toluene requires, therefore, 3 kilograms nitric acid a n d 9 kilograms sulphuric acid.

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This principle of chemical control is adopted#sometimes

in the two- and three-stage processes as well as in t h e stage process. T h e yield of T N T b y t h e one-stage process is 1.9 kilos per kilo toluene used.

The Two-stage P r o c e s s . There are two possible

modifications of the two-stage process:

1. Nitration from toluene t o M N T ; separation and purification of the mononitrotoluene, and n i t r a t i o n to T N T .

2. Nitration to dinitrotoluene, separation of this product from the spent acid, a n d further n i t r a t i o n to T N T .

T h e second modification h a s been practically dis-continued in this country, a n d will therefore n o t be discussed.

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THE MANUFACTURE OF TNT 35

t h a t it C£ya be safely distilled providing t h e r e is n o trinitrotoluene present. I n every case, however, t h e distillation should b e m a d e u n d e r reduced pressure, as t h i s lessens t h e danger from explosions.

Following t h e purification of t h e mononitrotoluene, or in case n o purification h a s been m a d e , following t h e separation from t h e spent acid, t h e mononitrotoluene is placed in t h e n i t r a t o r a n d is sulphonated w i t h a n a m o u n t of sulphuric acid equal t o t h r e e times t h e weight of t h e mononitrotoluene. T h i s requires a b o u t one-half hour. T h e reaction m i x t u r e is t h e n heated t o 70° a n d mixed acid containing 50 per cent each of nitric acid a n d sulphuric acid, equal in weight t o t h e sulphuric acid used for sulphonating, is a d d e d through a period of one hour. After t h e addition is complete t h e charge is cooked a t a t e m p e r a t u r e of 120° C. for two hours, t h e n separated, washed, etc.

T h e a m o u n t of acid necessary in t h e two-stage process per kilogram toluene is 5.6 kilos sulphuric, a n d 2.2 kilos nitric. T h e yield of T N T per kilo t o l -uene is 1.99 kilos.

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such t h a t t h e water concentration in t h e fi^jal mixture was about 4.4 per cent. T h e experimental d a t a indi-cate t h a t t h e yield of T N T a t a given t e m p e r a t u r e is n o t a function of t h e w a t e r concentration of t h e reac-tion mixture as assumed from

C6H4CH3NO2+2HNO3 z± C6H 2 C H 3 ( N O 2 ) 3 + 2 H2O .

I n his discussion H u m p h r e y makes perfectly clear t h e point t h a t the above s t a t e m e n t does not apply t o either very low or v e r y high w a t e r concentrations, because experiments have shown t h a t with a v e r y high w a t e r concentration t h e nitro-group enters t h e side chain of t h e toluene molecule, while w i t h a low w a t e r concen-tration, oxidation p r o d u c t s , such as trinitrobenzoic acids, result.

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THE MANUFACTURE OF TNT 37

T h e T h r e e - s t a g e P r o c e s s . T h e first-stage acid for this process is composed of 70 p e r cent sulphuric acid, 15 p e r cent nitric acid, a n d 15 per cent w a t e r . T h e acid is r u n i n t o t h e toluene, t h e addition generally t a k i n g a b o u t t w o h o u r s . T h e t e m p e r a t u r e during t h e addition of t h e acid m u s t n o t rise above 30° C. T h e proportion of acid to toluene is t h r e e t o one. Follow-ing t h e acid addition t h e t e m p e r a t u r e is raised t o 60° C , a n d is held a t t h i s p o i n t one a n d one-half h o u r s . T h e spent acid is t h e n separated, a n d t h e mononitrotoluene is either purified a n d n i t r a t e d t o dinitrotoluene, or t h e n i t r a t i o n is m a d e w i t h o u t a n y purification o t h e r t h a n the separation of t h e spent acid.

T h e acid used in t h e second stage contains 60 per cent sulphuric, 25 per cent nitric, a n d 15 per cent w a t e r . T h e acid is a d d e d to t h e mononitrotoluene a t 75° C , one a n d one-half hours being consumed in t h e opera-tion. After this addition h a s been m a d e , t h e charge is cooked a t a t e m p e r a t u r e of 90° for one a n d one-half h o u r s . T h e n t h e s p e n t acid is s e p a r a t e d , a n d t h e dini-trotoluene is r e a d y for centrifugalization, or n i t r a t i o n to T N T w i t h o u t purification.

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2.2. T h e total acid necessary is 2 kilos nitric a n d 5 kilos sulphuric per kilo toluene.

T h e German process of manufacturing T N T is of interest at this point, since t h e manufacture of this product originated in t h i s country. T h e two-stage process is the one in greatest use in Germany, a n d in m a n y plants t h e mononitrotoluene is separated, one of the isomers being used in t h e dye plants, while t h e other two are nitrated further to T N T . T h e first stage of the German process consists in placing 90 liters of toluene in t h e n i t r a t i n g kettle a n d adding a n equal volume of nitric acid (gravity 1.25) a t a t e m -perature of 30° or lower. B y using this acid alone, the Germans claim t h a t t h e separation of t h e o r t h o a n d p a r a mononitrotoluenes is effected more easily, a n d t h a t little or no T N T is present. T h e p a r a isomer is the one used for dyestuffs, a n d it is separated from t h e ortho and the small a m o u n t of m e t a b y cooling t h e mixture to 10° C. A t this t e m p e r a t u r e some of t h e p a r a mononitrotoluene separates out a n d m a y b e filtered off. If a complete separation is desired, a vacuum distillation of t h e mixture must be carried out. For nitration t o T N T only, no separation of t h e t h r e e mononitrotoluenes is necessary.

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THE MANUFACTURE OF TNT 39

temperature is t h e n raised to 120°, a n d held a t this p o i n t until t h e charges is finished as indicated by t h e control analyses.

In some p a r t s of (Jermany trinitrotoluene is ma.de from dinitrotoluene, which occurs as a b y - p r o d u c t in v a r i o u s processes of the m a n u f a c t u r e of other m a t e r i a l s . I n such a en.se, the dinitrotoluene is melted, s u l p h o n a t e d with one and one-fourth its weight of oleum, n i t r a t e d with threefifths its weight of nitric acid a t t e m p e r a -t u r e s varying from 100 -to VMY\ a n d finally s e p a r a -t e d from t h e spent, acid, washed a n d crystallized.

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tion of the higher grade of p r o d u c t t u r n e d out, £he three-stage process m a y be said to be the best.

M a n y engineers h a v e investigated to t h e extreme t h e conditions necessary for t h e best yields a n d t h e best product possible in t h e manufacture of T N T . M u c h credit is due one of these investigators, M . Coparisow, because of the light his research has t h r o w n u p o n t h e nitration of toluene, a n d t h e cure for t h e troubles encountered in this reaction. A s u m m a r y of Copari-sow's work is given here, it being t a k e n from a recent article. (3)

" T h e mineral m a t t e r present during t h e process of nitration m a y act either as a catalyst or as a chemical reagent, and this action m a y explain some of t h e curious occurrences in t h e course of a nitration. F u r -thermore, when mineral acids act u p o n t h e m e t a l p a r t s of the apparatus, hydrogen m a y be set free, a n d m a y reduce some of t h e nitro-compounds. U n d e r t h e working conditions amino groups m a y be diazotized yielding cresols a n d nitrocresols, whose salts are highly explosive, and this action m a y explain some of t h e heretofore mysterious accidents in T N T p l a n t s . These m a y be obtained as by-products, through t h e action of t h e hydrogen, a n d t h e oxidizing action of t h e nitric acid itself:"

" 1. Trinitrobenzoic acid and t e t r a n i t r o m e t h a n e . These result from oxidation in case of overheating or pressure. The intense odor of the t e t r a n i t r o m e t h a n e is sometimes observed in t h e factories, b u t t h e t r i n i -trobenzoic acid, owing t o its solubility, generally escapes detection.77

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THE MANUFACTURE OF TNT 41

nascent h y d r o g e n which is g e n e r a t e d b y t h e action of t h e acids u p o n t h e m e t a l of t h e n i t r a t o r . "

" 3. Sulphonic acids. T h e s e compounds m a y result

when t h e q u a n t i t y of sulphuric acid is too great; i.e., when t h e m i x t u r e of acid contains too m u c h sul-phuric acid in proportion t o t h e nitric acid."

I n t h e process of t h e m a n u f a c t u r e of T N T , Copari-sow points o u t t h e following as being m a t t e r s requiring p a r t i c u l a r care a n d watchfulness:

" 1. T h e a m o u n t of nitric acid used m u s t exceed t h e theoretical a m o u n t necessary b y a t least one-half molecule."

" 2. T h e extent of t h e n i t r a t i o n should be regulated more b y t h e concentration of t h e acids, t h e t e m p e r a t u r e a n d t h e d u r a t i o n of t h e n i t r a t i o n t h a n b y t h e actual q u a n t i t y of nitric acid p r e s e n t . "

" 3. T h e reaction p r o d u c t should n o t be kept in contact w i t h t h e spent acid longer t h a n is absolutely necessary."

" 4. T h e concentration of acid a n d t h e n a t u r e of the material in t h e p l a n t should b e such as t o reduce their action on one a n o t h e r t o a m i n i m u m . "

" 5. T h e r a w materials m u s t be p u r e . "

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Following t h e n i t r a t i o n of the T N T , e i t l ^ r one of two processes m a y be followed. T h e first of these processes consist in " blowing " the charge of T N T plus t h e spent acids t o a separating pan, where t h e charge is allowed to cool. On cooling, t h e T N T crystallizes out, a n d so separates from t h e spent acid. W a t e r is usually added to the mixture w h e n it is blown, in order t o more completely precipitate t h e T N T from t h e acid solu-tion. McHutchison a n d Wright (4) h a v e investi-gated the m i n i m u m a m o u n t of water necessary t o completely separate T N T from t h e m o t h e r liquor in order to avoid unnecessary expense in t h e recovery of t h e spent acids. I t was found t h a t t h e m a x i m u m p r e -cipitation of T N T occurred on the addition of t h e acid to 4 - 5 volumes of w a t e r . A greater dilution t h a n this, or the addition of t h e water to t h e acid was found t o be less effective. Following the separation, t h e spent acid is drawn off to a t a n k , and m a y either form t h e basis for the new n i t r a t i n g acid, or m a y be sent to t h e reclaiming plant for purification. T h e T N T is transported to t h e washing plant b y either m a n u a l labor, or b y melting a n d blowing t h r o u g h pipes or troughs.

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THE MANUFACTURE OF TNT 43

nitrating* acids. T h u s , t h e T N T in solution in t h e spent acid is reclaimed, so t h e percentage dissolved does n o t m a t t e r .

E v e n after t h i s s e p a r a t i o n of t h e spent acid, there still remains a considerable a m o u n t of acid in t h e T N T . I n order t o o b t a i n a m a r k e t a b l e p r o d u c t , this acid m u s t all b e washed out. T o perform this operation, t h e T N T is blown from t h e s e p a r a t i n g p a n or, if t h e separa-tion was m a d e in t h e n i t r a t o r , from t h e nitrator t o t h e washing t a n k s . T h e washing is accomplished b y m e a n s of h o t w a t e r (85 to 90° C.) Seven or eight changes of w a t e r are necessary for t h e complete removal of t h e acid.

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h a v e been used with more or less success I t h a s been found t h a t these m o r e distinctly alkaline salts t e n d to darken t h e T N T , a n d also t e n d to render it u n s t a b l e . There are, in fact, some sodium salts of T N T which explode as low as 160° C.

T h e washing of T N T is, in short, a chemical engineering problem which often taxes t o t h e limit t h e r e -sources of the engineer. Practice h a s proved t h a t t h e most efficient washing a p p a r a t u s is t h e most simple in construction. As a m a t t e r of fact, t h e more simple t h e entire T N T plant, t h e b e t t e r the product, a n d t h e most efficient t h e operation of t h e p l a n t . One t y p e of washer, a very complicated piece of a p p a r a t u s , built of iron, containing a lead lining, and well supplied w i t h baffle walls, interior wells, a n d valves a n d syphons galore, was a t one time in use a t a certain p l a n t . T h i s machine was a model of t h e designer's a r t , b u t was absolutely useless for t h e washing of T N T , since t h e charge generally finished u p b y solidifying in t h e various valves, wells, a n d syphons in and connected w i t h t h e machine. This necessitated dismantling t h e whole apparatus, and t h e cleansing of each individual valve a n d well with live s t e a m . Plain wood t a n k s h a v e now replaced this machine, a n d are washing t h e T N T perfectly, t h e entire t a n k costing less t h a n a new lead lining for the old t y p e a p p a r a t u s , and lasting from t w o t o three times as long. T h e agitation of t h e T N T a n d water in this wood t a n k is done b y means of compressed air or steam entering t h r o u g h small holes in a pipe r u n -ning lengthwise on t h e b o t t o m of t h e t a n k .

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THE MANUFACTURE OF TNT 45

order to^reclaim t h i s dissolved m a t e r i a l the wash water coming from t h e washers is r u n through a series of t a n k s containing baffle walls t o force t h e water t o t r a v e l a considerable distance. T h i s is known as t h e " labyrinth.7 7 H e r e t h e w a t e r cools, a n d t h e T N T is

t h r o w n o u t of solution. T h e s e labyrinths are cleaned o u t periodically, a n d t h e recovered T N T is melted, sieved, a n d if necessary t r e a t e d w i t h a nitrating acid a n d finished in t h e o r d i n a r y w a y . I n some cases this reclaimed T N T (sometimes of inferior quality) is mixed w i t h good T N T ( " b l e n d i n g " ) a n d is t h u s disposed of. T h e conscientious inspector of T N T will n o t allow this practice unless done under his personal supervision. Blended T N T possesses certain charac-teristics t h a t p u r e T N T does n o t possess, and m a y t h u s b e d e t e c t e d .

Following t h e washing, t h e T N T is crystallized or " grained.7' F r o m t h e washing t a n k or kettle t h e

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This is necessary t o p r e v e n t friction b e t w e e n r t h e a r m and t h e pan, a n d t h e possibility of ignition of t h e T N T . T h e a r m should be set in a sloping position w i t h t h e slope downward in t h e direction of r o t a t i o n . T h i s slope causes t h e T N T to climb over t h e arm, a n d greatly facilitates t h e graining of t h e material.

A second m e t h o d of reducing t h e T N T t o small particles, and which is, as yet, quite new, depends u p o n t h e rotation of a d r u m in t h e molten T N T . As t h e d r u m revolves, a t h i n layer of T N T adheres t o it, a n d is scraped from t h e d r u m b y a knife after a b o u t one-half revolution. This machine decreases t h e t i m e necessary for t h e crystallization greatly. T h e process is known as " flaking."

T h e completion of t h e crystallization m a r k s t h e end of t h e process of m a n u f a c t u r e of crude T N T . T h e only operation left is t h e screening. This is done b y shovel-ing t h e T N T directly from t h e crystallizshovel-ing a p p a r a t u s into an oscillating screen h a v i n g 10 t o 30 meshes per inch. T h e T N T passing t h r o u g h t h e screen is p a c k e d into boxes of 100 p o u n d s each.

One of the problems confronting t h e pioneer chem-ical engineers in t h e explosive field was t h e disposal of the spent or waste acid from t h e nitrations. T h e analysis of a typical s p e n t acid shows t h e following composition:

Nitric acid 3 - 1 2 % Water 10-30 Organic m a t t e r |—3 Sulphuric acid Balance

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-THE MANUFACTURE OF TXT 47

tion to t h e spent acid tank, and from this place to the denitrifying plant. Modern practice utilizes the spent acid from one stage as the ba^is of the nitrating mix-ture for the next preceding stage. This re-use is along certain lines t h a t are developed by the individual plant. This method of using the spent acid over again possesses the following advantages:

1. T h e saturation of each spent acid with organic m a t t e r lessens the loss of t h e T X T b y solution.

2. A uniform spent acid is discarded b y the nitra-tion plant, thus enabling t h e denitrating plant t o adopt a standard practice, a n d t o treat each batch of acid the sanie.

T h e first step in the reclaiming of the spent acid is the cooling a n d filtering of the acid. This removes a large p a r t of the organic m a t t e r . The removal of the organic m a t t e r is very important, especially so if the recovered nitric acid is to be used in the manufacture of ammonium nitrate. Foreign material in the nitric acid ma}' result in an explosion. In the United States alone, at least one explosion is known to have been caused b y such contamination.

Following the removal of t h e organic matter, the acid goes to the denitrating plant. Here the nitric acid is separated from the sulphuric acid b y blowing air a n d steam through the mixture. The weak nitric acid resulting from the solution from the denitrating towers is used, as stated above, in the manufacture of ammonium nitrate.

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granted in 1914, separates the nitrotoluenes c o n t a i n e d in the waste acid b y washing the acids with toluene or a nitrated toluene which h a s been n i t r a t e d to a lower degree than t h a t of t h e products to be removed. If t h e process be carried o u t a t a suitable t e m p e r a t u r e , t h e toluene or nitrotoluene used for t h e e x t r a c t a n t undergoes nitration in t h e process. Fresh nitric acid m a y be added to the waste acids for this purpose.

Another process of extracting t h e organic m a t t e r , from the waste acids b y solvent means was p a t e n t e d in 1915. (6) This process is made continuous b y r u n -ning together t h e waste acid and solvent, in suitable proportions, into a mixing tank, while maintaining t h e appropriate t e m p e r a t u r e a n d pressure. T h e m i x t u r e flows from the mixing t a n k through a n overflow pipe into settling tanks, where t h e liquids divide into layers, t h e nitrotoluenes formerly dissolved in t h e acids being now dissolved in t h e solvent. Suitable solvents men-tioned in the process are toluene, mononitrotoluenes, etc.

A distillation process is interesting because of its uniqueness. I n t h e operation of this process (7) t h e waste acid is e v a p o r a t e d in a suitable container, a n d the organic substances are removed from the gas a n d vapors b y passing these vapors t h r o u g h a chamber over water. T h e p a r t n o t absorbed b y t h e w a t e r in this chamber passes o u t into a condenser. T h e solidified organic m a t t e r collects in a readily accessible chamber, a n d is removed from time t o time.

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super-THE MANUFACTURE OF TXT 4M

p h o s p h a t e , from t h e Russian phosphate rock. T h e s u p e r p h o s p h a t e t h u s prepared is said to be much more d r y a n d more pulverulent t h a n t h a t made with sul-p h u r i c acid alone.

A f t e r t h e separation of the nitric acid from the solu-t i o n , solu-t h e r e remains a mixsolu-ture of sulphuric acid ar.d w a t e r . T h i s is concentrated b y running slowly through a s e r i e s of pans, called a " cascade/7 which are heated

f r o m b e n e a t h . Various other patented processes are

n ^ w c o m i n g into use for concentrating sulphuric acid

s o l u t i o n s . T h e acid coming from the concentrating p l a n t is mixed with oleum to further reduce the water c o n t e n t , a n d m a y b e used in nitrating mixtures again. A n o t l i e r use for the acid as it comes from the concen-t r a concen-t i n g house is in concen-t h e manufacconcen-ture of niconcen-tric acid.

A n o t h e r problem which the engineer must meet is t h a t of transferring the T N T after it has been completed b y n i t r a t i o n t o the various other stages of the manu-f a c t u r i n g process. W i t h the toluene, acids and other r a w m a t e r i a l s this is comparatively easy, since these are i n t h e liquid s t a t e . T X T , however, will solidify at 8 O ° C . a n d m u s t be kept above this temperature if it is t o b e blown through pipes. Blowing consists in run-n i run-n g t h e T N T irun-n a molterun-n state irun-nto a strorun-ng box called a cc b l o w - c a s e , " a n d then, b y means of compressed

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good plan to overcome this difficulty is to r u » t h e T N T through very short pipes, b y gravity, or where a short pipe is not feasible, a t r o u g h m a y be m a d e , a n d sur-rounded b y steam pipes embedded in asbestos cement or sand. Should t h e T N T solidify through accident, t h e trough can be readily cleaned out without delay or inconvenience.

T h e oily substance which separates on t h e second stage of t h e three-stage process, called b y t h e G e r m a n s " binitrotropfol," is q u i t e indifferent to a t t e m p t s m a d e to n i t r a t e it. T h e problem has been solved in Italy, according t o Giua, i n this m a n n e r : (9)

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THE MANUFACTURE OF TNT 51

centrifuged t o s e p a r a t e t h e oil. B y t h e above m e t h o d of n i t r a t i n g , a great a m o u n t of t h i s oil h a s been saved. I t will b e seen from t h e foregoing description of t h e complete m a n u f a c t u r e of T N T t h a t t h e modern fac-t o r y m u s fac-t b e m u c h larger fac-t h a n a simple nifac-trafac-ting, washing a n d crystallizing p l a n t . T h e m o d e r n p l a n t m u s t include, besides t h e T N T u n i t s : (a) P l a n t for m a n u f a c t u r i n g nitric acid; (6) Sulphuric acid concen-t r a concen-t i o n p l a n concen-t ; (c) d i n i concen-t r a concen-t i n g a n d filconcen-tering p l a n concen-t ; (d) a m m o n i u m n i t r a t e plant, or other p l a n t to utilize t h e w e a k nitric acid t h a t is recovered from t h e spent acid.

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T H E PURIFICATION OF T N T

T H E purification of T N T , while in reality a p a r t of its manufacture, m a y consist of any one of a n u m b e r of methods, most of which are equally good as a m e a n s of extracting t h e " impurities " in t h e T N T . T h e r e are appearing every d a y new m e t h o d s of purifying this substance, and t h e n u m b e r is now too great t o t r e a t each method separately. I t is thought wise, in view of the fact t h a t a differentiation is m a d e between crude and purified T N T , t o t r e a t t h e purification as a sepa-r a t e subject, sepa-r a t h e sepa-r t h a n to include it in t h e discussion of the manufacture.

T h e product which results from t h e application of the various processes outlined in the previous chapter is known as " crude T N T .7 7 T o define t h e word

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THE PURIFICATION OF TNT 53

these a r e jthe " impurities " m e a n t when this t e r m is used in connection w i t h T N T .

B y referring t o t h e chapter on " T h e N i t r a t i o n of T o l u e n e " i t is seen t h a t T N T m a y contain mono-nitrotoluene, dinitrotoluene a n d even other isomeric trinitrotoluenes aside from t h e symmetrical T N T . T h e c o m m o n expression " T N T " (or its synonyms) h a s become narrowed down t o m e a n t h a t certain trinitrotoluene isomer defined as t h e alpha, or 1-2-4-6 isomer. T h e melting-point of t h i s particular trinitro-toluene as determined b y r e p u t a b l e authorities is 80.6 t o 80.8° C. Now, if o t h e r trinitrotoluenes or a n y m o n o - or dinitrotoluenes be mixed w i t h t h e symmetrical T N T , t h e melting-point will b e either raised or lowered, according t o t h e specific nitrotoluene present. As a general rule, t h e melting-point of t h e mixture is lower t h a n t h e melting-point of p u r e T N T , indicating t h e pres-ence of some of t h e m o n o - a n d dinitrotoluenes. I n order t o remove these c o m p o u n d s from t h e T N T , m a n y different m e t h o d s of purification are resorted t o . T h e greater n u m b e r of these m e t h o d s depend u p o n the solvent action of some s u b s t a n c e u p o n the-mononitro-toluenes a n d t h e dinitrothe-mononitro-toluenes. T h e more i m p o r t a n t of t h e s e m e t h o d s are outlined below.

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with the t o p of t h e T N T . At this p o i n t#a further

amount of alcohol equal t o one-quarter t h e weight of the T N T is added, a n d the filter is sucked d r y . T h e T N T is dried b y either a current of w a r m air, or b y vacuum. I n the l a t t e r case, the filter m u s t be so ar-ranged t h a t a v a c u u m m a y be effected in t h e upper chamber.

T h e action of the first portion of alcohol a d d e d is to dissolve t h e mononitrotoluenes a n d t h e dinitro-toluenes. T h e second volume added dilutes this solu-tion and dissolves a n y of the nitrotoluenes which escaped solution b y t h e previous addition. T h e last portion of alcohol serves to dissolve out a n y remaining traces of the impurities, a n d also serves to wash the T N T .

The cost of this m e t h o d of purifying T N T is r a t h e r high. P u r e ethyl alcohol is preferable t o denatured alcohol, because of t h e action the denaturing agents have on the T N T . T h e cost of the u n d e n a t u r e d sol-vent is too high, however, to permit its use unless a well-developed plan of solvent recovery is in operation, so t h a t practically none of t h e solvent is lost.

Figure

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References

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