He assumed the role of a state supervisor for the German-Russian community, first in German book censorship, later (1801) as the manager of German-language theaters.
[6] From the end of Napoleonic Wars until his death in Saint Petersburg, Adelung was involved in sorting, reviewing and categorizing the European manuscripts related to pre-Petrine Russian history.
He published biographies and critical assessments of Sigismund von Herberstein (1818), August von Meyerberg (1827), Conrad Bussow and other major sources on Muscovy; the work culminated in Kritisch-literarische Übersicht der Reisenden in Rußland bis 1700 (Critical bibliographical review of the memoirs by travelers into Russia prior to 1700).
In a completely unrelated effort, Adelung compiled a bibliography of then known Sanskrit sources; an abridged version of his work has been since regularly reprinted (latest English reissue: 2008).
Adelung's elder son Karl (1803–1829) joined Russian diplomatic service and was killed in Tehran together with Alexandr Griboyedov.