During the expedition, Iradier - accompanied by his wife, sister-in-law and others, traveled almost 1,900 kilometres (1,200 mi) from Aye up to the Muni River.

The expedition reached the islands of Corisco and Elobey Grande, as well as Inguinna and San Juan, the Utongo and Bathe rivers, as well as the Paluviole and the Saw of Crystal mountain ranges.

Iradier mapped the regions he had visited and, on his return to Spain, these were published by the Company of Africanists and Colonistas of Madrid.

His second expedition began at the end of 1877 during which he recorded vocabularies and grammars of the languages of the tribes he encountered, as well as numerous astronomic, ethnographic, climatological and commercial observations.

In February 1885 he submitted to the Company of Africanists and Colonists of Madrid various documents, contracts of annexation and notarial deeds, incorporating the territories of the river Muni under Spanish sovereignty.