pharmaceutical secondary standard; traceable to USP, PhEur and BP Synonym(s): Allopurinol; 1 H -Pyrazolo(3,4-d)pyrimidin-4-ol; 4-Hydroxypyrazolo(3,4-d)pyrimidine; 4-Hydroxypyrazolo[3,4-d]pyrimidine; HPP Empirical Formula: C5H4N4O Formula Weight: 136.11 Linear...