336 SHORT PAPERS [,.Z?zalyst, Vol. 91 The Detection of Dinitro and Trinitro Aromatic Bodies in Industrial Blasting Explosives BY S. A. H. AMAS AND H. J . YALLOP (Royal Armament Research and Development Establishment, Fort Halstead, Kent) THE detection and identification of nitro-bodies is a common requirement in the explosives labora- tory. Janowski’s reactionf provides an adequate test for dinitro and trinitro aromatic compounds by means of the characteristic colours developed in alkaline acetone. In the forensic laboratory, however, these compounds normally have to be detected as minor constituents in small samplesMay, 19661 SHORT PAPERS 337 of industrial blasting explosives. For this purpose J anowski’s reaction has been found unsatis- factory, particularly when applied as a spot test.The reason for this is that the test is insufficiently sensitive, and so an attempt has been made to effect a n improvement. It has been found that this gives better results with forensic samples than any other of a range of organic solvents tested. The alkali normally used for this reaction is potassium hydroxide, 5 per cent. being the commonly recommended strength. It was found, however, that the sensitivity of the test was increased if stronger alkali was used. This agrees with the observations made by English on alcoholic sodium hydroxide. The limit of detection for 2,4-dinitrotoluene was found t o be 20 pg with 10 per cent. potassium hydroxide, improving to 1 p g with 50 per cent. potassium hydroxide. Because very strong alkali is not a convenient reagent for bench use, alternatives were con- sidered.It was known that coloured complexes are formed between some nitrobodies and organic bases,3 and this reaction forms a convenient technique for colouring trinitrotoluene in crystal struc- ture investigation^.^ A range of organic bases was therefore studied, and three emerged as giving good colour reactions with di- and trinitrotoluene a t low concentrations. These were tetramethyl- ammonium hydroxide, diethylene triamine and tetraethylene pentamine. For use as a bench reagent, 25 per cent. aqueous tetramethylammonium hydroxide was found to be the most con- venient since it is a clear mobile liquid that can be used satisfactorily with a dropping bottle. The reaction can be readily carried out on a spot plate. The addition of a 5 to 10-mg specimen of one drop of acetone - alcohol, and one drop of tetramethylammonium hydroxide produces a blue colour with dinitrotoluene and a dark red with trinitrotoluene.The initial colour should be observed since changes occur with time. A slight yellow is produced with nitroglycerine so that if this is present thc colour produced with dinitrotoluene is green. The test has been applied to a wide range of obsolete and current industrial blasting explosives, and i t has been found that none of the other components present interfere with the reaction. The limits of identification are 4 p g for nz-dinitrobenzene, 2 pg for 2,4-dinitrotoluene and 1 pg for 2,4,6-trinitrotoluene. English2 has described the use of 50/50 acetone - alcohol as a solvent. REFERENCES 1. 2. 3. 4. Janowski, J. V., Ber., 1886, 19, 2155. English, F. L., Analyt. Chem., 1948, 20, 745. Davis, T. L., “The Chemistry of Powder and Explosives,” John Vc’ilcy and Sons Inc., Sew \*ark, Yallop, H. J., Analyst, 1960, 85, 300. 1941, Volume 1, p. 135. Received August 17th, 1965