phosphoramide hexamethylphosphoric triamide HMPT phosphoric hexamethyltriamide phosphoric acid hexamethyltriamide N,N,N',N',N'',N''-hexamethylphosphoric triamide N,N,N',N',N'',N''-hexamethylphosphoric triamide Hexamethylphosphoramid hexamethylphosphoric acid triamide HEMPA phosphoric tris(dimethylamide) HMPA hexamethylphosphoric triamide hexamethylphosphoramide HMPTA Hexamethylphosphorsaeuretriamid hexamethylorthophosphoric triamide mutagen insect sterilant