Picric acid is known to react with metals to form highly unstable metallic picrates, which are known to have been involved in serious explosive accidents. In this study, transition-metal picrates of chromium, manganese, cobalt and nickel salts are synthesized, and the thermodynamic and explosive properties (for example, initiation sensitivity) are examined.
The decomposition of Mn-picrate or Co-picrate determined through differential scanning calorimetry (DSC) begins at a lower temperature than that of picric acid, and the heat of decomposition of transition-metal picrates is found to be lower than that of picric acid. Thermogravimetry and Karl Fischer analysis confirm that transition-metal picrates contain crystal water, and the amount of crystal water in metastable-phase picrates is determined experimentally. Thermogravimetric analysis reveals that crystal water begins to dehydrate in a temperature range extending from slightly above room temperature to approximately 470 K. The activation energies of the decomposition reaction of these transition-metal picrates are 204.1 kJmol-1 for Cr-picrate, 108.1 kJmol-1 for Mn-picrate, 132.3 kJmol-1 for Co-picrate, and 184.3 kJmol-1 for Ni-picrate. Drop-hammer test results show that Cr-picrate has higher strike sensitivity than picric acid, and friction tests reveal that all of the transition metal-picrates examined here have equal or lower friction sensitivity compared to picric acid.