That same year, he participated in organizing the workers' congress of Barcelona, over which he presided. In September 1869, he attended the fourth congress of the First International in Basilea, representing the "Federation of Workers' Societies of Barcelona". There he made the acquaintance of Mikhail Bakunin. They struck up a friendship immediately because of their common interest in music. He also became a member of Bakunin's International Alliance of Socialist Democracy and created an autonomous Catalan branch of that group. He was an organizer and president of the workers' congress of Barcelona in 1870, a constituent of the Spanish Regional Federation of the International Workers Association (IWA). Two years later he participated in the congresses of the IWA in The Hague, where he came out strongly against the expulsions of Bakunin and James Guillaume. For the remainder of his life, he was a determined advocate of Bakuninism as the foundation of anarchism in Spain.