INDUSTRIAL A N D ENGINEERING CHEMIXTRY
January, 1923
73
Estimation of t h e Proportions of TNT and Tetryl from the Freezing Point Curve'*2 By C. A. Taylor*and W. H. Rinkenbach' PITTSBURGH EXPERIMENT STATION,BUREAUOF MINES, PITTSBURGH, PA.
flaky crystals of faint YelIn this paper data and a curoe therefrom showing the equilibrium low tint. The setting Point and tetryl are used diagram of the binary system TNT-tetryI have been obtained, in certain types the existence of a neu molecular complex, 2C7HbN806:C7Hfla08. Was 128.72" c. of detonating fuses and may has been indicated, and practical use for the data has been outlined. METHOD be found in detonators. The method of determinAt present there is no satisfactory method of estimating the proportions of the two ing the equilibrium temperatures of known mixtures of T N T substances. The method usually used is to determine the and tetryl was that described by Bell and Sawyer,s and Bell total nitrogen by the Dumas method and calculate the ratio and Herty.0 As used in this work, carefully weighed quanof the ingredients using the known nitrogen content of pure tities of the two substances were transferred to a glass tube TNT and tetryl as a basis. This method is tedious, and a 3 / ~in. in diameter and 11 in. long. This tube also containea small error in the result of the analysis causes a large error in a' - carefully calibrated thermomthe proportions calculated. The binary system of T N T and tetryl was studied in order eter reading from to obtain data that could be used in analytical methods and 0" to 150' C. and a looped wire stirrer as physical constants in other work. held in place by a MATERIALS cork. The tube and contents were TRINITROTOLUENE-This was prepared by recrystallizing heated until the Grade I commercial T N T from' hot benzene after filtering substances had to remove any insoluble matter. The crystals were air- melted and formed dried to remove mechanically held benzene. They were then a clear, homogenerecrystallized from boiling 95 per cent ethyl alcohol. The ous liquid. This light yellow, fluffy crystals were redissolved in hot 95 per t u b e was t h e n cent ethyl alcohol and then crystallized by pouring the solu- jacketed by means tion into about two volumes of distilled water. The mix- of a tube 12 in. ture was allowed to stand for several hours in a dark place long and 13/4 in. in to cool and complete crystallization. The crystals were d i a m e t er, t h e then rapidly filtered on a Buchner funnel, washed several mouth of the times with cold, dis- smaller tube being 45 tilled water, and flush with the cork given a final rinse of the jacket. The 65h IO PO 30 40TN I:50FER60CENT70 BO 90 /C with cold, 95 per cent jacket-tube was alcohol in order to 42 then immersed as FIG.2 f a c i l i t a t e drying. far as possible in a The mass of crystals 5-liter beaker of was dried on filter water or oil, maintained a t a constant temperature somepaper, and kept in what below the crystallizing temperature of the mixture under sulfuric acid desicca- observation, this having been roughly determined in advance. tors in a dark place. Upon agitating the liquid mixture by means of the wire The final product stirrer, the temperature fell a t a uniform rate. TemperabB was a mass bf very 3 5 k U 0 ZW, 300 4 D U 5i0-600 700 800 900 /000M!O TIME, SECONDS light, fluffy, white ture readings were taken every minute and in some cases every FIG.1 microscopic crystals. half minute. After falling for some time, there would be a The T N T did not rike in the temperature coincident with the appearance of a develop any color during 6 mo. storage in a dark room. The solid phase. After attaining a maximum, the temperature would again fall a t a time rate lower than that observed setting point was 80.27" C. TETRYL-A good grade of commercial tetryl was purified before the appearance of the solid phase. Such a typical in the same manner as the TNT. Efforts to obtain colorless cooling curve is shown in Fig. 1, temperatures being plotted as tetryl proved unsuccessful. The material precipitated in abscissas and time readings as ordinates. Guia,' working upon the nitrotoluenes, took the point B the water from the hot alcohol appeared colorless, but as soon as it was filtered a faint yellow color developed, even (Fig. l), a t which crystals first appeared, as the equilibrium temperature of the mixture. Bell and Herty,6 however, when the work was done in a dark room. The final product of this purification was a mass of light, in repeating this work, showed that, although point C is nearer the true value than B, the true value, C', may be ob-
M
XXTURES of T N T
s'
1 2
* 4
Received July 29, 1922. Published by permission of the Director, U. S. Bureau of Mines. Explosives Chemist, U. S. Bureau of Mines. Assistant Explosives Chemist, U. S. Bureau of Mines.
6 6
7
THISJOURNAL, 11 (1919),1025. Ibid., 11 (1919),1124. Bey., 47 (1914), 1718; GQZZ.chim. i f a l . , 111 46 (1915),339.
74
INDUSTRIAL A N D ENGINEERING CHEMISTRY
tained by extrapolating the second and slower rate of cooling upon the initial rate of cooling. Accordingly, this method of deriving the true equilibrium temperature was used by the writers. Upon continuing the cooling it was found possible to determine the eutectic point of the mixture with some concentrations, while with others the proportion of the solid phase was so great that after a time it was found impossible to stir and so insure equal cooling throughout. The results obtained follow, and are shown in the form of an equilibrium diagram in Fig. 2. TNT
Per cent 0.00 10.00 24.89 40.00 44.16 49.52 50.00 52.08 52.50 55.12 61.61 65.00 75.00 76.13 SO. 40 82.31 89.50 90.00
100.00
Tetryl Per cent 100.00 90.00 75.11 60.00 55.84 50.48 50.00 47.92 47.60 44.88 38.39 35.00 25.00 23.87 19.60 17.69 10.50 10.00 0.00
Extrapolated Point, C’ O
121.1 107.5 90.8
Eutectic Point
c.
128.72
120.8 90.9
76.8 75.4
75.5
70.8
70.8
70.4 70.95 72.7 73.0 76.45 76.3
c.
67.4 67.6 67.4 67.6 67.6 67.4 67.6
67.4 67.6 67.5 67.4
76.4 80.27
TNT-TETRYLCOMPLEX When concentrations of from 55 to 65 per cent of T N T were studied, it was found that there was no preliminary separation of a first solid phase and then gradual temperature decrease to the eutectic point. Instead, over this concentration range the temperature fell below the eutectic point, a solid phase appeared, and the temperature of the mixture rose to the eutectic point. When the values obtained were plotted in the form of an equilibrium diagram (Fig. 2) and these points connected, it was apparent that there were two eutectic points, connected by an almost straight line curve. This indicates the existence of a compound of the components, and calculation shows that a mixture of 61.27 per cent T N T and 38.73 per cent tetryl has the proportions of two molecules of TNT to one molecule of tetryl. The straight line indicates that the melting point of the complex is near the eutectic temperatures, and the method is not sufficiently sensitive to give the curve that probably occurs at that point. Melts containing 40, 60, and 80 per cent of T N T were sub-
Rare Books The library of the Chemists’ Club, New York City, has a small collection of interesting rare books. Assuming that our readers would be interested in knowing of the existence of such a collection, Miss E. J. Fell, the librarian, has prepared the following chronological list of the most ancient of these works: Aretino: “De metallicis libri tres.” Noribergae, 1602. Croll: “Basilica chymica.” Frankfort, 1620. Agricola: “De re metallica.” Basil, 1621. Linceo: “Discorsi dimostrazioni matematiche.” Leida, 1638. Bertereau: “La restitution de pluton.” Paris, 1640. Glauber: “Operis mineralis.” 3 vols. in 1. Amsterdam, 1651-2. Paracelsus: “Opera omnia medico, chemico, chirurgica.” 3 vols. in 2. Geneva, 1658. Boyle: “Chymista scepticus.” 2nd edition. Rotterdam, 1668. Guericke: “Experimenta nova (ut vocantur) Magdeburgica d e vacuo spatio.” Amsterdam, 1672. Borrichius (Ole Borsch) : “Hermetis Aegyptiorum et chemicorum sapientia.” Hafniae, 1674. Leeuwenhoek: “Arcana naturae ope microscopiorum detects.” Delphis, 1695. Manget: “Bibliotheca chemica curiosa.” 2 vols. Geneva, 1702.
Vol. 15, No. 1
mitted to W. M. Myers for examination under the petrographic microscope. He found that the 40 per cent T N T mixture contained tetryl and a compound other than TNT; the 60 per cent T N T mixture appeared to be almost entirely this compound; the 80 per cent T N T mixture was a mixture of free T N T and this compound.
APPLICATION OF
THE
DATA
When the time rate of cooling is plotted on a large scale, the C’ point can be checked to 0.2”, and this point can be determined in the curve to 0.2 per cent. If no C’ point is found, showing the T N T content to be between 55 per cent and 65 per cent, it is still possible to determine the percentage with a fair degree of accuracy by adding a weighed portion of either T N T or tetryl to a weighed portion of the unknown mixture so as to make the T N T content less than 55 per cent or greater than 65 per cent and then determining the C’ point of this new mixture. Knowing the weights of unknown mixture and pure component, and the percentage of TNTin the new mixture as found from the curve, the proportions of the substances present in the original mixture can be calculated : A = Wt. of sample. , B = Wt. of component added as TNT. x Per cent of component (TNT) which was originally present in sample. y = Total per cent or component (TNT) present in new mixture as found from curve. Y (A B) - 100B. Then A
-
+
If a C’ point obtained on an unknown mixture is between 67.5” .and 80.3” C., there is no means of knowing whether the point is on the tetryl or TNT side of the curve. This can be determined by changing the proportions as given above, locating another point in the curve, and noting whether the temperature is higher or lower than the original. It is usually more satisfactory to add tetryl for this purpose than TNT. Grade I materials are usually used in the detonating fuse SO that the error due to impurities as TNT is comparatively small. ACKNOWLEDGMENT The authors gratefully acknowledge the helpful suggestions and criticisms of Mr. A. C. Fieldner and Mr. R. E. Hall, and the assistance of Mr. W. M. Myers, who did the petrographic work on melts.
Lemery, Nicolas: “Dictionaire; ou, trait6 universe1 des drogues simples; pharmacopke universelle.” 4th edition. Rotterdam, 1727. Boerhaave:,‘ “Elementa chemiae.” 2 vols. .Paris, 1732. Lavoisier: Opuscules physiques et chimiques.” Vol. 1. Paris, 1774. Dalton: “New system of chemical philosophy.” 2 vols. in 3. Manchester, 1808-10.
American Academy Makes Grant At a meeting of the Committee on the C. M. Warren Fund of the American Academy of Arts and Sciences, held on December 8, 1922, a grant of $250.00 was made to Prof. James B. Conant, of Harvard University, to be used in furthering his research in connection with the electrochemical study of the reversible reduction of organic compounds. The next meeting of the committee for the warding of grants will be held on March 1, 1923. Applications for these grants must be in the hands of the chairman of the committee, Prof. James F. Norris, Massachusetts Institute of Technology, Cambridge, Mass., before this date.
