Vogt was appointed professor of metallurgy at the University of Christiania in 1886. His first important work, Studier over slagger (1884; “Studies on Slags”), began a series of studies on molten slags (slag), in which he examined the crystallization of furnace slags and pointed out the close resemblance in mineral composition and texture between slags and certain igneous rocks. His principal work on slags, Die Silikatschmelzlösungen (“The Molten Silicate Solutions”), appeared in 1903–04. Vogt's studies served as a starting point in applying the known laws of solutions to the crystallization of igneous-rock magmas, and his pioneer work did much to stimulate the quantitative research that followed. In 1912 he took the chair of mineralogy at the technical high school at Trondheim, retiring 16 years later.