In 1860 he published the pamphlet "Salus Publica Suprema Lex," urging the reorganization of the army.
Successively member of the Zollparlament and of the imperial Reichstag, Friedenthal was prominent in the proposal and passage of many bills.
From October 1877 to March 1878, during the absence of Friedrich Albrecht zu Eulenburg, he was head of the Ministry of the Interior.
In the same year he was elected member of the Upper House, but in 1881 resigned, and retired to the management of his estate, Giesmannsdorf, near Neisse.
Besides his doctor dissertation, "De Rerum Litigiosarum Alienatione ex Jure Romano" (1845), Friedenthal published "Reichstag und Zollparlament"