Minol II (40% ammonium nitrate, 20% aluminum) is useful as an explosive fill for bombs, because its use substitutes cheap, and abundant, ammonium nitrate (AN) for more expensive, and sometimes scarce, TNT. However, Minol II exhibits poor dimensional stability when exposed to temperature cycles during storage. It has been shown that growth of Minol II charges during temperature cycling is caused by the polymorphic phase transition which occurs in AN above 32C. Review of the literature suggested that this phase transition could be prevented by substitution of a solid solution of potassium nitrate (KN) in AN for AN in explosive compositions. Some of the reported properties of such solid solutions (KN-AN-III or AN-KN) have been confirmed. Charges containing 40% TNT, 40% AN-KN and 20% aluminum (now designated Minol IV) showed better dimensional stability during temperature cycling than either TNT or TNT/ aluminum (67/33).

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