Chemical analysis of extracting transition metal oxides from polymetallic ore by sulphate process Otgon-Uul Enkh-Uyanga, Baatar Munkhtsetseg, Urtnasan Urangoo, Enkhtur Tserendulam and Davaadorj Agiimaa EPJ Web Conf., 140 (2017) 13004 Published online: 30 June 2017 DOI: 10.1051/epjconf/201714013004