1,4-Dihydrazinophthalazine hydrochloride 2,3-Dihydrophthalazine-1,4-dione dihydrazone monohydrochloride 63868-75-7 C-7441 Dihydralazine hydrochloride EINECS 264-519-6 Phthalazine, 1,4-dihydrazino-, hydrochloride