Events in the year 1850 in Brazil. Incumbents Monarch – Pedro II Prime Minister – Marquis of Monte Alegre Events September 4: Law n° 581, known as the Eusébio de Queirós Law, is passed, which extinguishes the African slave trade to Brazil.Lei N° 581, de 4 de setembro de 1850, no site do Palácio do Planalto. Births January 17: Joaquim Arcoverde, cardinal References