THE COLLIERY GUARDIAN AND JOURNAL OF THE COAL AND IRON TRADES. Vol. CX. FRIDAY, OCTOBER 8, 1915. No. 2858. Experiments with Ammonium Nitrate Explosives.* By H. SCHMERBER. The purpose of the researches and experiments detailed in the paper was to obtain data for enabling an approximate idea to be formed as to the characteristics —temperature of detonation, force, etc.—of mixtures of ammonium nitrate explosives without long and delicate theoretical calculations or preliminary tests in practice. The present series of experiments was conducted with binary mixtures, but the method adopted would be equally applicable to ternary or multiple mixtures. They were restricted to the determination of the two most important characteristics of an explosive—the tempera- ture (t) of detonation, and the explosive force (/)—the former playing an important, if not capital, role in the case of special explosives, whilst the force affords a o 02 02 '7500 '5500 fOOO '5500 9000 '.7000 3692 8633 "o F pou '1900° f I poU( 1500° >F lour 1300' Nitrote > pur 8t32 J 85 53 Fpot '1500 5500 85% 86 87 88 89 90 91 92 93 94 95 96 97 9 8 99 100*. Content of ammonium nitrate. Fig. 1.—Diagram of f Values up to the Limit of Complete Combustion. Mixture of ammonium nitrate with carbon with the toluene and naphthalene series. Pour = for. Binitrotoluol = binitro toluene. Binitro- naphtaline - binitronaphthalene. Monitronotoluol = mononitrotoluene. Mononitronaphtaline — mono nitro- naphthalene. Charbon = carbon. N aphtaline = naphtha- lene. Toluene = toluene. Pur = pure. The values of f for 1500° and 1900° are indicated by the larger black dots, the smaller dots indicating the intermediate mixtures. general idea of the value of an explosive, without intro- ducing special factors such as the density of the charge. All the mixtures examined were composed, on the one hand, of ammonium nitrate, and, on the other, of the combustible substances most usually employed in the explosives industry—carbon, naphthalene, toluene, nitro derivatives of naphthalene, toluene and xylene, nitro-glycerine, picric acid, and endecanitrocellulose. In a series of binary mixtures of ammonium nitrate, with, for example, trinitrotoluene, the one extreme member of such a series, pure trinitrotoluene, detonates perfectly, in spite of its lack of oxygen, whilst the other extreme member, ammonium nitrate, detonates only imperfectly under the ordinary conditions of practice. Of the inter- mediate members, the series containing an excess of nitrate undergoes, by reason of the excess of oxygen, * From the Bulletin of the Society de I’lndustrie Minerale. complete decomposition into carbon dioxide when detonated. The limit point of complete combustion is reached with that member of the series which contains just enough excess oxygen, from the nitrate, to trans- form all the carbon of the second ingredient of the mixture into CO2. Beyond this point follows a second series, in which the oxygen no longer suffices for the production of C02, so that CO, CH4, etc., etc., are formed. The same series of phenomena is reproduced, whatever the combustible substance used; but the series of mixtures capable of forming explosives will be more or less restricted, according to the detonative faculty of the combustible. It follows, therefore, that the study of any binary mixture will divide itself into two parts :—(1) The phase of complete combustion, with excess of oxygen—comprising all the mixtures with a relatively low temperature of detonation, and suitable for use in fiery mines; and (2) the phase of incomplete combustion, more or less extensive according as the second ingredient is more or less explosive by itself. The exception to this rule is the series in wThich nitro- glycerine is used, in which case—this substance itself containing an excess of oxygen—complete combustion occurs with all the members of the whole series. In determining the explosive force and -the tempera- ture of detonation, these values were first calculated for 7 000 9500 907 9000+^ 8500' 8932^ . 8710+. 8000\ 10084- 7500^*" iwoo^B^poo^ +1900* 19lrf\ 7000\ ■ ■ ■ u 19\ S^spo0 5500! : ■ '"'"I 5000', • ! • § io 1 Si tot 60%- 65 70 75 80 85 90 95 '00% Content of ammonium nitrate. Fig. 2.—Diagram of f Values up to the Limit of Complete Combustion. Mixtures of ammonium nitrate with picric acid, nitroglycerine, and bi- and trinitrotoluene and naphthalene, &c. Nitroglycerine = nitroglycerine. Coton endicanitrique = endecanitric cotton. Acide picrique = picric acid. Trinitrotoluol = trinitrotoluene. Trinitronaphtaline — trinitronaphthalene. Binitrotoluol = binitrotoluene. Binitronaphtaline = binitronaphthalene. the mixtures of limit composition, and then, the chemical formulae of two or three mixtures out of those containing an excess of oxygen, the values t and f being also calculated for these products. On the other hand, the characteristics of ammonium nitrate being known, it was easy to ascertain the values t and / for any mixture giving complete combustion, all that was necessary being to plot curves by taking the percentages of ammonium nitrate as abscissae and the values of t and f respectively as ordinates. These curves possess real interest, especially in connection with explosives for fiery mines, since an examination of the diagrams affords useful indications for preliminary trials. The tempera- ture curves show at once the composition of mixtures detonating at 1,500 and 1,900 degs. Cent., whilst the force curves show what power these mixtures may be expected to exert. Another point of interest about the force curve is that it shows whether any advantage is to be gained, in the case of mixtures high in the combustible ingredient, by producing incomplete combustion. Picric acid, for instance, explodes with great violence, though devoid of oxygen; but it is desirable to know whether its explosive force can be raised by adding the oxygen that is lacking. The investigation therefore divides itself into two parts : First, the study of the curves t and / up to the complete combustion limit (this group com- prising all the safety explosive mixtures); and secondly, the study of the curves—that of the explosive force in particular—beyond that limit, and verifying experi- mentally the force developed by mixtures which give incomplete combustion. The curves represented in fig. 1 relate to complete- combustion mixtures of ammonium nitrate with naphthalene, toluene, carbon, mononitronaphthalene, mononitrotoluene, binitronaphthalene, and binitro- toluene respectively, and were established from the following data :— Ammonium nitrate and naphthalene :—The limit of complete combustion is attained with 6-25 per cent, of naphthalene and 93-75 per cent, of nitrate; the calcu- lated values for t and f being, t = 2,122 degs. Cent, and f = 8,449. The intermediate points were obtained with, 3*85 per cent, naphthalene and 96-15 per cent, nitrate, t = 1,766 degs., f= 7,347; and with 1-96 per cent, naphthalene and 98*04 per cent, nitrate, t — 1,430 degs., f = 6,246. Ammonium nitrate and carbon:—Limit mixture, 6-98 per cent, carbon and 93-02 per cent, nitrate, t = 2,107 degs., f = 8,179. Intermediate mixtures, carbon, 3-62 per cent.; nitrate, 96-38 per cent.; t = 1,643 degs., /= 6,824; and carbon, 2*44 per cent.; nitrate, 97-56 per cent.; t = 1,465degs., f = 6,269. Ammonium nitrate and toluene :—Limit mixture, 6-01 per cent, toluene and 93-99 per cent, nitrate, t = 2,100 degs., f = 8,497. Intermediate mixtures, toluene, 2-80 per cent.; nitrate, 97-20 per cent.; t = 1,597 degs., f = 6,816; and toluene, 1-88 per cent.; nitrate, 98-12 per cent.; t = 1,432 degs., / = 6,240. Ammonium nitrate and mononitronaphthalene :— Limit mixture, mononitronaphthalene, 9-14 per cent.; nitrate, 90-86 per cent.; t = 2,171 degs., / = 8,553. Intermediate mixtures, mononitronaphthalene, 5-13 per cent.; nitrate, 94-87 per cent.; t = 1,735 degs.,