248 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 12, No. 3 ACTION OF SODIUM. CARBONATE ON TETRYL which have been under more or less discussion since Having proved that m-nitro-tetryl may be satis- the outbreak of the war. factorily removed from tetryl by means of sodium I-As an indication of the stability of tetryl, ordi- carbonate, it appeared advisable to determine the nary qualitative heat tests are of little value. effect of this alkali on tetryl itself. After a thorough 11-The Obermuller or gas evolution test in vacuo laboratory investigation it was shown conclusively shows the true stability of tetryl to be indicated by that sodium picrate was the sole reaction product the melting point, to which it is directly proportional. when sodium carbonate acted on tetryl. 111-The instability of ordinary tetryl is due to a During the reaction the whole nitromethylamine large extent to the presence of tetranitrophenylmethyl- radical is replaced by the ONa group, nitrous acid nitramine (m-nitro-tetryl). This impurity is formed being evolved. As might be expected, this reaction by nitration of the monomethylaniline present in takes place to a greater extent on boiling tetryl with the dimethylaniline used. caustic alkalies, sodium or potassium picrate being IV-The nitration of pure dimethylaniline under formed with the liberation of methylamine. With ordinary conditions gives no m-nitro-tetryl. sodium carbonate solutions the rate of hydrolysis of V-m-Nitro-tetryl is unstable and its presence tetryl is relatively slow. However, sufficient sodium greatly decreases the stability of tetryl. picrate was prepared in this manner to carefully study VI-m-Nitro-tetryl may be removed from tetryl its properties and prove its identity. The picric acid by boiling with water, by which it is converted into after acidification and recrystallization melted at soluble trinitromethylnitramidophenol, and more read- ily by a sodium carbonate solution, whereby the 122. 5' C. and showed a molecular weight of 129, the theory for picric acid. soluble sodium salt of styphnic acid (trinitroresorcinol) is formed. DETECTION OF SODIUM PICRATE IN TETRYL VII-Tetryl is slightly hydrolyzed by a dilute Since sodium picrate is very soluble in water, it sodium carbonate solution to sodium picrate. appears that any of this compound formed would be VIII-Sodium picrate is insensitive and stable and easily removed by the subsequent water washes after its presence does not lower the stability of tetryl to neutralization. To settle this point, a sensitive test any appreciable degree. for the determination of small quantit:es of sodium IX-Sodium carbonate is a very satisfactory sta- picrate in tetryl was developed and it was found that bilizing agent for tetryl. It removes acidity and such none:of this product could be detected in our finished impurities as m-nitro-tetryl. Any sodium picrate tetryl nor in our second wash water after the alkali formed and not removed by washing is non-injurious boil. This indicated that any sodium picrate formed to the tetryl. was removed by the first water wash. EFFECT OF SODIUM PICRATE ON STABILITY OF TETRYL THE MANUFACTURE OF TRINITROXYLENE FOR USE AS A SUBSTITUTE FOR TNT IN BURSTING CHARGES Since sodium picrate is a relatively stable explosive, FOR HIGH EXPLOSIVE SHELL' it is difficult to conceive of its lowering the stability By John Marshall of tetryl and its complete removal seems of little im- EASTSRNLABORATORY, E. I. DU FONT DE NEMOURS& CO., CHESTER, PA. portance. Varying mixtures of tetryl and sodium picrate have been carefully made up and the stability From its physical properties trinitroxylene, or and sensitiveness determined. Even large quanti- TNX, would appear to be most unfavorable for use ties of sodium picrate were found to affect the tetryl as the bursting charge for high explosive shell. The melting point of the predominating isomer is very but slightly. high, 182' C., making it impossible to load by direct The addition of I to IO per cent sodium picrate to tetryl has no effect on the drop test, the mixture giv- casting. Moreover, this compound is almost insolu- ing a detonation in each case with a 4 oz. weight at ble in other lower melting nitro bodies at low tempera- 14 in., the drop test for pure tetryl. Pure sodium tures such as are preferable for casting, seemingly pre- cluding the casting of such a mixture. It has not picrate cannot be detonated with an 8 oz. weight at more than 80 per cent the explosive strength of TNT, 24 in. and it is much less sensitive to detonation. The acute The addition of IO per cent of picrate to tetryl was situation which developed in the TNT supply in the found to lower the melting point by only 0.6' C., while the presence of smaller amounts could hardly summer of 1917, however, made it necessary to con- be detected from thc drop in melting point, indicating sider the use even of materials which appeared un- that the stability of the material was not impaired. favorable. About this time it was suggested by a member of the du Pont Company's chemical depart- ILloreover, the stability of mixtures of sodium picrate and tetryl gave approximately the same gas evolution ment that TNX might be used to advantage as a test as pure tetryl. The decomposition in vacuo partial substitute for TNT by casting a mixture of TNX suspended in molten TNT. of a mixture containing IO per cent sodium picrate was less than that for ordinary crude tetryl. Experiments were immediately started at the Eastern Laboratory for the preparation of a few pounds of CONCLUSIONS TNX for experimental purposes. The nitration process It is hoped that this discussion of the stability of 1 Presented at the 58th &Meeting of the American Chemical Society, tetryl has brought out the following points, most of Philadelphia, Pa., September 2 to 6, 1919. Mar., 1920 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY 249 itself offered many difficulties, but a few pounds were difficult owing to the viscous nature of the charge prepared, and a study made of the use of the com- in the nitrator. pound in a shell bursting charge. 2-It was necessary to separate the crystalline Rather to the surprise of those concerned, TNX product from the spent acid by filtration, followed by proved to be almost ideal for the purpose. When 30 a secondary separation of the oily products not held to 50 parts of TNX were suspended in 70 to 50 parts by the filter. of TNT at 100' C. a sufficiently fluid mass was ob- 3-The yield of desirable product was greatly low- tained to admit of direct casting without the use of ered owing to the loss of material in the form of oil, any extruding mechanism. The castings when which obviously could not be used in shell loading. cooled proved to be completely amorphous, resembling &--When washing the oil-contaminated crystals paraffin in texture. They showed no segregation of with boiling water in the neutralizing process, there either component of the charge, were remarkably was a tendency for the crystals to cement together free from air holes, showed high and uniform densi- in small lumps, which included small quantities of acid ties, were non-hygroscopic, and showed no tendency from the wash waters. This acid could be finally re- to become oily or leaky, even on storage at elevated moved only with great difficulty. temperatures. They could be completely detonated The first requirement was therefore the production with smaller primers of tetryl than could castings of of a homogeneous material, and for this three methods TNT alone. They could be drilled with ease for of procedure were open: first, by using pure m-xylene; booster cavities, and in fragmentation tests showed second, by increasing the severity of nitrating condi- results approaching those obtained with refined TNT. tions to the point of partial oxidation of the 0- and Added to these advantages, it was found that more +isomers and more complete nitration of the un- satisfactory castings could be obtained with a mix- oxidized residue; and third, by controlling the composi- ture of crude TNX and crude TNT than with refined tion of the raw material so as to partially exclude the materials, which in itself would produce a considera- undesirable isomers. ble saving in both operating and material costs. THE NITRATION OF PURE "-XYLENE Since the potential supply of xylene in the country Pure m-xylene is easily prepared by the partial was at least 20 per cent of the supply of toluene, the sulfonation of the mixed xylenes, followed by steam development of a manufacturing process for TNX distillation of the sulfonated product for the regenera- was immediately advisable and the study was at tion of the m-xylene. once undertaken. m-Xylene thus prepared, having a boiling range of The development of the manuf acturing process 0.4' C., was subjected to a three-stage nitration and from the laboratory scale to the design, construction, gave an almost pure trinitroxylene melting above and operation of a large scale plant occupied more than I 75' C. It was found, however, that the solid product a year and a half, and production was proceeding was precipitated in the final nitration in a very finely rapidly at the time of the signing of the armistice. divided crystalline form that made the charge ex- The details of the work done during this period are tremely viscous. This could not be overcome ex- manifestly beyond the scope of this paper. It will cept by using prohibitive amounts of nitrating acid be attempted, therefore, only to outline the difficulties to obtain the necessary fluidity.