870
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
few tests with non-corrosive priming compositions and a low-pressure nitrocellulose powder have shown t h a t corrosion from the nitrocellulose powder probably occurs only with extremely low confining pressures, such as those of blank cartridges. N o nitrocellulose corrosion followed the use of a low-pressure gallery powder confined behind the full weight 0.3ocaliber bullet. SUMMARY
A review of the scientific, patent, and trade literature, and the compilation of the experiences of many practical riflemen has indicated much confusion in theories dealing with t h e after-corrosion of firearms and much divergence in the practices recommended for prevention. Generally this corrosion has been attributed t o acid products on the bore, although other explanations, including the action of chlorides, have been advanced. A critical laboratory study, comprising t h e exposure of fired rifles and fouled barrel sections t o known humidities, t h e chemical examination of the corrosive residue, t h e use of special ammunition, and the analysis and testing of many "nitro-solvents" and other compositions recommended as preventatives showed the following: The present high-pressure smokeless cartridge leaves no nitrocellulose residue and no corrosive acid residue. After-corrosion following the use of such cartridges is caused by the explosive deposition of a water-soluble salt or salts in whose aqueous solution steel corrodes, together with subsequent exposure t o a high humidity a n d the presence of oxygen. I n the present service ammunition this salt is potassium chloride from the decomposition of the chlorate in the primer. Such water-soluble salts are retained in tool wounds and Dits on the bore surfaces in which they cannot be seen from the breech or muzzle, and from which they cannot be removed mechanically. They are easily dissolved by water or suitable aqueous solutions. After-corrosion may also be prevented by keeping both ends of the bore tightly corked. The present service ammunition can be rendered non-corrosive by eliminating the chlorate of the primer. It may be possible t o develop a non-corrosive primer which will not affect the present ballistic properties of this cartridge. This point is under investigation. A number of non-aqueous compositions recommended for cleaning firearms possess little or no value. Their supposed virtue apparently rests upon tests conducted a t humidities so low t h a t no corrosion couldoccur. After-corrosion proceeds below t h e dew point. A simple test for differentiating between worthless and valuable cleaning compounds is described. Corrosion from nitrocellulose powder probably occurs only when the confining pressure is extremely low, as in blank cartridges. ACKNOWLEDGMENTS
The writer wishes particularly t o acknowledge the assistance of Mr. A. C. Fieldner, supervising chemist, and Dr. E. W. Dean, petroleum chemist, of the Pittsburgh Station of the Bureau of Mines, and of Dr. G. A. Hulett, Dr. C. E. Munroe, and Major General F. C. Ainsworth, U. S. A. (retired).
Vol.
12,
No. g
STRENGTH AND VELOCITY OF DETONATION OF VARIOUS MILITARY EXPLOSIVES1 By W. C. Cope EASTERN LABORATORY, E. I. DU PONT
DE
NEMOURS & CO., CHESTER, PA.
During the past three years many tests on military explosives have been conducted a t the laboratory and a t the proving ground of this company. I t would not be possible t o review in a short paper all the d a t a accumulated. This discussion, therefore, will be limited t o the strength, velocity of detonation, and fragmentation tests of some of those military explosives t h a t were used or proposed for use during the war. STRENGTH
One of the first considerations of a military explosive is t h a t of strength. The delivery of the explosive a t the desired point by shell, or other means, is so expensive t h a t i t is desirable t o have as strong a n explosive as. possible. Various methods have been proposed a n d used for determining strength, but the one found most satisfactory is the ballistic mortar, by means of which the various explosives are tested for strength in comparison with a standard explosive whose properties are generally well known. The ballistic mortar used in the author's work is similar t o the one described by Comey and Holmes,2 and its construction and operation are briefly as follows: Length of pendulum, I D ft.; weight of mortar, 5 2 4 lbs.; diameter of explosion chamber, 2 in. ; length, j.5 in. ; diameter of shot chamber, 47j8 in.; length of shot, 5 in.; weight of shot, 36.5 lbs. Ten grams of T N T are shot in the mortar, followed by t h a t weight of the explosive under test, as found by trial shots, which will deflect t h e mortar approximately an equal number of ballistic degrees. TABLEI TNT Value in EXPLOSIVE Ballistic Mortar Tes Ammonium nitrate.. ......................... 10.51 Ammonal Ammonium nitrate 8 9 . 0 11.2 T N T (crude) 6.01 A1 5.0 Amatol (hot pressed) Ammonium nitrate 80.0 20.0 , , , . . . . . . . . . . . . . . . . 12.1 TNT
...................
1 1.................. 50.0
Amatol (melt). Ammonium nitrate 5 0 . 0
TNT
Ammonium nitrate 20.0 TNT TNX(trinitroxy1ene) 10 .O Ammonium Trinitroanisol nitrate
. . . . . . . . . . . . . . . . . . . 11.9
;;;E ] . . . . . . . . . . . . . . . . . . .1 1
; ; ; 1
.9
. . . . . . . . 10.51
........ Nitrostarch (12.8 Picric acid.. ..... Tetranitroanil Tetranitromet Trinitroanisol
11.8
8.6
. . . . . . . . . . . . . . . . . . 12.1 ryl). . . . . . . . . . . . . . . 12.1 . . . . . . . . . . . . . . . . . .10.6
..................................
9.3
Calculated values: see page 871.
The T N T value of t h e explosive is obtained by calculation. For example, if i t required 11.5 g. of a n explosive t o deflect the mortar the same number of degrees that 10.0 g. of T N T would deflect it, the T N T 1 Presented at the 59th Meeting of the American Chemical Society, St. Louis, Mo., April 12 to 16, 1920. 2 8th Intern. Congr. A p p . Chem., 26 (1912), 209.
Sept., 1920
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
value would be I O . O / I I . ~ X I O or 8.7, and the explosive would be 87 per cent as strong as T N T . I n Table I are given the T N T values of the most common explosives t h a t were used in the World War. Other explosives are also included in order t o give a n idea of t h e relative strengths of explosives with which we are more or less familiar. The figure for ammonium nitrate was derived by calculation from results obtained, when it was substituted in various percentages in dynamite, since ammonium nitrate itself is not sufficiently sensitive t o detonation b y means of a blasting cap. To make these substitutions trustworthy, i t was necessary t o maintain an equal excess of oxygen in all the dynamite mixtures. Ammonal was an explosive used in mining and sapping operations, of about the same strength as 6 0 per cent nitroglycerin dynamite made with active base. Amatol was one of the most important military explosives used in the war, but, since the so-called “melt” amatol was not sensitive enough to detonation with a blasting cap, it was necessary t o obtain results on dry mixed, materials. Ammonium picrate also was not sensitive enough with blasting cap, and its strength was calculated from substitution in various dynamite mixtures. While not detonating completely with a blasting cap, ammonium picrate when shot in t h e mortar with a No. 6 cap had a T N T value of 8.24, and when shot with a special tetryl blasting cap had a value of 9.9. The strength of high-grade nitrocellulose is greater than perhaps would be expected, b u t this material has a very low den_sity, hence its limited application. Nitroglycerin is included t o show t h a t it surpasses in strength explosives t h a t are generally regarded as very strong. T N A and tetryl have the same strength, while hexanitrodiphenylamine is intermediate between these explosives and T N T . Although picric acid is stronger t h a n T N T , its use as a military explosive has been limited because of its cost, the large amount of raw materials required for i t s production, and difficulty in loading. I n spite of these objections, it was used t o a considerable extent b y the French and Italians. VELOCITY O F DETOKATIOS
A high velocity of detonation is greatly desired in military explosives, especially those t h a t are contained i n steel shells, for the reason t h a t , t o be effective for a great distance, the fragments from the shell should be animated with a high velocity. Although the chemical constitution of an explosive controls its velocity of detonation, the latter can be altered1 t o a certain extent by varying: ( I ) The diameter of the explosive column. (2) The density t o which the explosive is pressed. (3) The method of confining t h e charge. Six explosives, representing material largely used or proposed for use as shell fillers, were tested for velocity of detonation under the following conditions. The explosives were cast or malleted into wroughtiron pipes, 1 2 in. long, 1 9 / ~ in. ~ inside diameter, with ‘ / 8 in. wall thickness. The pipes were open at both ends when the explosive was detonated. A 1
Marshall, “Explosives,” 2 (1917), 482.
871
hole, I in. in diameter and z in. in depth, was drilled in one end of the explosive column. This hole was loaded with 2 8 g. tetryl in which a KO. 6 blasting cap was imbedded, which served as primer and booster in detonating the explosive under test. At distances of 4 and I O in. from the booster end of the pipe, 9/32-in. holes were drilled t o take the velocity cap and cordeau as employed in the Dautriche method of testing; and on the opposite side of the iron pipe, 9/32-in.holes were drilled 5 and I I in. from t h e booster end of the pipe. The purpose of the two sets of holes was t o obtain simultaneous velocity records on the one test piece. The velocity figures obtained from the two records were averaged, as i t was believed t h a t this would give more trustworthy results. The method of obtaining the velocity of detonation was t h a t of Dautriche, using detonating fuse, as described by Comey.’ The velocity of the detonating fuse was accurately determined by means of a recording chronograph of t h e Mettegang type, and was found t o be 5 3 0 0 m. per sec. The results of tests on six explosives are shown in Table 11. T N T sample No. 168, having a melting point of 80.1’, was used in all tests except B , where crude T N T melting a t 7 7 . 3 ’ was used. The T N X was granular in structure and had a freezing point of 163’. Two samples of ammonium nitrate were used, having the following characteristics: SAMPLE. .....................
. A N N o . 276 Per cent NHaN03 (purity). . . . . . . . . . . . . . . . . . . 9 9 . 0 Granulation 20-40 mesh
....................
37.0 27.0
AN No. 279 Per cent 98.1 67.0 24.0 6.0 3.0
.................... TOTAL . . . . . . 100.0 100.0 The results in Table I1 show t h a t T N T gave t h e highest velocity, and t h a t for shell fillers any one of the six explosives would be satisfactory. The mean variation of velocity is within zoo m./sec., which is probably as near as could be expected by this method, when taking a record on a high velocity explosive on a column only 6 in. in length. The mean variation of 230 m./sec. for Explosive B, which consisted of a mixture and not a homogeneous compound like Explosive A, is considered very good. It should be noted t h a t crude T N T was used ,in this mixture, which would give a lower velocity t h a n the refined material. Explosive C gave a greater variation in velocity figures than might perhaps be expected. This is not attributed t o the method so much as t o the composition itself. I t i s well known t h a t in melt amatol, containing only 40 per cent ammonium nitrate, the nitrate has a tendency t o settle out of suspension. Since the mixture is not homogeneous the velocity results should be expected t o be somewhat erratic. I n Explosive D, the 5 0 : jo melt amatol gave very concordant results, which may be accidental, or due to t h e homogeneity of t h e mixture. Ammonium nitrate has less tendency t o settle out of suspension in 5 0 : jo amatol t h a n from mixtures containing less nitrate. 1 7 t h Intern. Congr. A#*. Chem., Sb (1909), 30.
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
872
TABLE 11-VELOCITY OF DETONATION OP
EXFT,OSIVE
COMPOSITION
A T N T (80.1')
Density.. . . . . . . . . . . . . . . . . . . Velocity, m./sec.
..........
1.91
[ E% 7960
.................... 7600 ............. 191
Average., Mean variation..
B T N T (77.3') T N X (163') 1.56 6525 6970 6920 7175 7390 7000 230
60 40
C T N T (80.1') ANNo. 276 1.59 7595 6660 8125 7000 7820 7440 488
The variable velocity results of Explosive E may be attributed t o the settling of the nitrate. The coarse nitrate has more tendency t o settle than the fine. Explosive F, hot pressed amatol, had a mean variation of 2 6 1 m./sec., which is considered very good for a mixture. These velocity figures probably are fairly comparable with those obtained in explosive shells. One important point brought out is t h a t coarse ammonium nitrate does not have any deleterious effect on the velocity of melt amatol, especially if there is 5; per cent T N T present. To show the effect of density on velocity of detonation, a few tests are recorded on tetryl and T N T . Tetryl, when hand tamped into a 1 . 2 j X 8 in. paper dynamite cartridge shell t o a density of 1.0,had a velocity of 5450 m./sec., and, when compressed into pellets, 1.2; in. in diameter and I in. long, with a density of 1.40, and thesepellets were wrappedin paper, a velocity of 7300 m./sec. was obtained. Since the diameters were equal, the increase of 185 m./sec. must be attributed t o a n increaseof 0.4 in density. TNTwhen hand tamped into 1 . 2 j-in. dynamite cartridges t o a density of 1.0, gave a velocity of 4600 m./sec. No figures are available for velocity of TNT'compressed into pellets of the same diameter and shot under exactly the same conditions. F R A G iUE N T A T I 0 N T E S T S
The brisance of an explosive is usually referred t o as its violence or shattering effect, and this characteristic is due to two properties, zliz., strength and velocity of detonation, but it is not known exactly how great a value should be given t o each when obtaining the value of brisance by calculation. A practical way of determining brisance is by means of fragmenting steel shells filled with explosives, and comparing the fragments with those obtained from a shell loaded with T N T as a standard. Just what constitutes suitable fragmentation is not clearly defined. Naturally, when a shell detonates, it is blown into various sized pieces, some of which are no larger than a pin head, and, as would be expected, these small pieces are not effective, except perhaps t o blind a person. For the above reasons pieces of a certain size are arbitrarily considered as effective, and shell fragments are counted on this basis, usually taking T N T as a standard. I n our early work on fragmentation i t was customary t o count the fragments held on a 2mesh screen, and those passing a 2-mesh screen and held on a 6-mesh screen. As this involved considerable work, a revised method was used, which consisted in counting the fragments held on 2 - and on 4-mesh screens. On account of this change in procedure, i t will be necessary t o give two tables showing the frag-
60 40
SIX
Vol.
12,
No. 9
EXPLOSIVES D
T N T (80.1') AN No. 276 1.56 7000 6880 7235 7070 6930 7020 103
E
TNT (80.1')
50 50
ANNo.279 1.55 7065 6715 7920 6565 6880 7030 371
55 45
T N T (i0.1") ANMo. 276 1.40 5775 5655 6135 5680 6360 5920 261
20 80
mentation of shells containing the explosives shown under velocity of detonation. All the explosives shown in Table I1 are not given under fragmentation, because i t was necessary t o use a different kind of shell on some of the tests. TABLE111-FRAGMENTATION TESTS ON 3-IN. TONATING SHELLS
EXPLOSIVE
u. s.
A
ARMY BASE DE-
-
B P COMPOSITION T N T (80.1 ") T N T 76 6') 60 TNT (80.1") 60 T N X l165.6') 40 ANI (No.277) 4 0 Density of explosive 1.60 1.56 1.59 Weight of explosive (g.) 449 432 465 Weight of tetryl in fuse (g.) 28.1 28.1 28.1 Weight of shell (grams) 5608 5642 5662 Weight of fuse (grams) 616 616 616 Metal recovered (grams) 6103 6226 6142 Metal recovered (per cent) 98.0 99.4 98.2 Per cent metal recovered Held on 2-mesh 56.7 59.9 63.5 Held on 6-mesh 37.4 * 35.5 32.3 6C 5.9 4.6 4.7 Number of fragments Held on 2-mesh 204 179 Held on 6-mesh 3087 2824
-
TOTAI.~
1 2
--
-
3291 3003 2744 Fine crystalline ammonium nitrate, 97.5 per cent NH4NOs. Represents average of 5 tests.
The shell chosen for most of our fragmentation work was the U. S. Army 3-in. base detonating shell, fire& by means of a medium caliber base detonating fuse. This fuse is very efficient from the standpoint of detonating explosive mixtures, although not from ai mechanical point of view. The 3 in. shell was chosen because fragmentation pits will not stand up long under the action of larger shells. The fragmentation pit was cylindrical in shape, I O f t . in diameter and 11 f t . high, with a concave roof held in place by sand ballast. TABLEIIV-FRAGMENTATION TESTSON TONATING
EXPLOSIVE COMPOSITION
A
TNT (80.0')
Density of explosive Weight of explosive (g.) Weight of tetryl in fuse (g.) Weight of shell (grams) Weight of fuse (grams) Metal recovered grams) Metal recovered {per cent) Per cent metal recovered Held on 2-mesh Held on 4-mesh Held on 6-mesh 6+ Number of fragments Held on 2-mesh Held on 4-mesh
1.6 505 28.0 5668 616 6090 96.9 58.1 33.3 4.1 4.5 195 1495
-
3-IN. U. S. ARMY BASE DE;
SHELLS F
G TNT(80.0') 20 T N T (80.0') 20 AN' (No. 283-A) 80 T N X (168') 10 AN2 (No. 292) 70 1.4 1.5 422 454 28.0 28.0 5623 562b 616 616 6100 6181 97.8 99.0 70.2 23.9 3.0 2.9 193
868 1061
TOTALS 1690 62-per cent passes 60 mesh, 96.8 per cent NH4NOs. 92 per cent passes 60 mesh, 96.0 per cent NH4NO8. 3,Represents average of 5 shots.
73.8 20. T 2.7 2.8 220
890 -
1110
1 2
On the base of the pit was a n anvil on which t h e shells exploded when dropped through a 4 in. iron pipe entering the top of the pit. The pit was constructed of I-in. boiler plate reinforced by wooden piles, a n d had the necessary entrance for workmen, and port holes for the gases t o escape. The shell was placed in a crad1e:on a platform 2 j r f t . above the pit and armed.
Sept
,
1920
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
T h e operator retired behind a barricade and inverted t h e cradle by pulling a wire, causing t h e shell t o slide down the pipe, where i t detonated on t h e anvil. After the gases resulting from t h e detonation had been cleared out, workmen swept up the fragments in the pit. The results of the fragmentation tests with various explosives are shown in Tables I11 and IV. Explosive A, containing TNT alone, gave a greater number of fragments t h a n Explosives B or C. Likewise Explosive B gave more fragments t h a n Explosive C. This is no doubt due t o the greater brisance of Explosive B as compared with Explosive C. I n Table IV, T N T is shown t o be superior t o the other two explosives, due t o greater brisance. While Explosives F and G are stronger than T N T , the latter has a higher velocity of detonation, and this characteristic seems t o overbalance the inferiority in strength, within certain limits. The fragmentation results indicate t h a t any of these explosives would be satisfactory as shell fillers. S U &I MA R Y
I-The strength of several explosives, used or proposed for military use, is given, as compared with T N T , t h e comparison being based on the results of the ballistic mortar test. 2-The velocity of detonation of several military explosives has been determined under known conditions of density and confinement. 3-Several military explosives have been detonated i n steel shells, and the resulting fragments have been compared as t o number and size with those obtained when using T N T as a standard bursting charge.
873
tremuloides) after extraction with ether, alcohol, a n d water. Schwalbe and Beckerl have analyzed typical species of German woods and obtained results which on the whole correspond satisfactorily with those of Schorger for similar American woods. K6nig and Becker2 have examined several European woods particularly for their non-cellulose content. Determination of lignin by four different methods gave surprisingly concordant results. The pentosan-free cellulose values obtained by difference are much lower t h a n those obtained by Schwalbe and Becker using the chlorination method. A proximate analysis of five California woods has been made by D ~ r e . ~ These contributions, as well as earlier ones, are characterized by the diversity in form of material employed for investigation and also b y suggested modifications in methods, apparatus, or procedure, particularly for the determination of cellulose. Schorger4 .has pointed out t h a t one of the most important points in determining cellulose consists in obtaining the sample in proper physical condition, and Schwalbe6 has indicated the necessity of further standardizing methods and apparatus for the analysis of all fibrous raw materials. It is the purpose of this paper t o give some data, obtained in connection with the analysis of woods, which have a bearing on these two problems. EXPERIMENTAL^ THE
EFFECT
OF
SIZE
OF
PARTICLE
ON
YIELD
OF
CELLULOSE-wood is exceedingly difficult t o disintegrate uniformly, and material in a uniform s t a t e of division and composed of particles of rather limited dimensions appears t o be of prime importance for t h e determination of cellulose if comparable results are SOME OBSERVATIONS ON THE DETERMINATION t o be obtained. OF CELLULOSE IN WOODS1 I n the application of their chlorination method By S. A. Mahood t o wood Cross and Bevan7 state t h a t i t should be reFORESTPRODUCTSLABORATORY, U. s. DEPARTMENT OF AGRICULTURE, duced “to a state of the finest possible division,” MADISON, WISCONSIN Some time ago the Forest Products Laboratory and suggest the use of a fine plane for this purpose. Dean and Towers found ground wood passing a a4-mesh took up the systematic study of t h e chemistry of sieve unsatisfactory, but obtained more suitable American woods. The results of a preliminary study material by using a woodworker’s rasp and removing of the subject were published in 1917 b y Schorger.2 the fine particles from the sample by sifting through The complex nature of wood from a chemical point of view, together with the scattered and incomplete cheese cloth or a very fine sieve. Sieber and Waterg inforrnation on methods, necessitated confining the used finely rasped wood graded to pass through a No. 7 5 sieve but not through a No. 110. method of attack t o the determination of a number of Schorger used shavings not over 0.00; in. thick from constants under arbitrary but rather well-,defined conditions which would show ( I ) possible variations which all particles passing a 40-mesh sieve had been in the composition of the different woods, and ( 2 ) removed. Johnsen and Hovey employed raspings the presence and percentage of constituents of possible passing an 80-mesh sieve but not a Ioo-mesh sieve. commercial value, in addition t o those already known; Dore’s samples consisted of “fine sawdust,” while and which would give data upon which conclusions Schwalbe and Becker and Konig and Becker analyzed might, be drawn regarding the chemical constituents material in the form of wood flour (holzmehl). The variations t h a t may be obtained by using maof wood as a whole. Since the publication of Schorger’s results several contributions t o the subject of wood chemistry have been made. Johnsen and Hovey3 have investigated balsam fir (Abies balsamea) and aspen (Populus 1 Read at the Symposium on Cellulose Chemistry at the 59th Meeting of the American Chemical Society, St. Louis, Mo., April 12 to 16, 1920. 2 THIS JOURNAL, 9 (1917), 556, 561. Fa9er, 21 (1917-18). No. 23, 36.
Z . angew. Chem., 32 (19191, 229. I b i d . , 32 (1919), 155. a THIS JOURNAL, 11 (1919), 556. 4 Lac. c i t . , p. 566. 5 2.angew. Chem., S i (1918), 193; J . Sac Chem. I n d . , 37 (1918). 685a. 6 Acknowledgment is made to Mr. D. E. Cable for assistance in securing 1
2
the experimental data given. 7 “Cellulose,“ 1903, 266, 244. 8 J . A m . Chem. Sac., 29 (1907), 1121, 1125. 9 P a p i e r f a b r i k . , 11 (1913), 1179; J . SOC. Chem I n d , 32 (1913), 974
