In 1823 while still in the small laboratory at Nørregade he identified a new family of sulfur-containing compounds, calling them xanthates (xanthus, Greek "yellow") on account of the predominantly yellow colour of xanthate salts. Zeise was accordingly awarded a silver medal by the Royal Danish Academy of Sciences and Letters, and he became a member of that body the following year on the recommendation of Ørsted. In 1836 he became a Knight of the Order of the Dannebrog, a very high honour bestowed by the Danish monarch.