Solubility estimations for two selected explosives

Available data have been collected on the solubility of cyclotrimethylenetrinitramine (RDX) and cyclotetramethylenetetranitramine (HMX) in selected solvents from literature and experimental studies. Literature has been searched for solubility theory and estimation techniques. Using one of these techniques for the activity coefficient estimation, the UNIFAC method, combined with an equation for the estimation of solid-liquid solubility, predictions have been made for the solubilities of RDX and HMX in acetone, cyclohexanone, and acetic acid. These predictions have been compared with the available experimental data. The solvents selected are used extensively in RDX/HMX production operations.

Results from the model indicate a deviation from the experimental data ranging from close agreement to a maximum 88% deviation for RDX and a maximum 200% deviation for HMX systems. The percent deviation was smaller at the higher temperatures. The temperature range investigated was 30 to 90 degrees centigrade. The deviation may be due in part to the lack of precise data for the heat of fusion of these explosive compounds as analyses show the estimated solubility values are especially sensitive to that particular parameter.

Additional work, both experimental and theoretical, appear to be required in order to provide better solubility estimation techniques for compounds in this class, that is, compounds for which methods are unknown for determining melting points and heats of fusion.