This article shows how scientific travels contribute decisively to the construction of expert authority. An example of this can be observed in studying the work of the chemist José Casares Gil (1866-1961), who, together with other Spanish scientists, made several trips to European and Latin American countries. Some had formative and academic objectives, but others were related to diplomacy and cultural mediation in different spaces. Furthermore, he formed part of institutions that promoted scientific exchanges to modernize pedagogical practices in the teaching of chemistry in Spain and in America. But he was also a chemist who developed links and networks of contacts among a variety of different countries, which benefited both the institutions involved and the experts themselves who thereby strengthened their own scientific authority.