In 1797, he acquired the porcelain manufactory in Volkstedt (a suburb of Rudolstadt), which he sold two years later.
After the dissolution of the kingdom of Westphalia, Ernst Constantine succeeded his brother Louis as Landgrave of Hesse-Philippsthal in 1816.
Ernest Constantine died on 25 December 1849 in Meiningen and was later buried in Philippsthal.
[1] Ernest Constantine married Louise (1775-1808), the daughter of Prince Frederick Charles of Schwarzburg-Rudolstadt (1736-1793), on 10 April 1796 in Rudolstadt, with whom he had the five children: Later, he married his niece, Caroline of Hesse-Philippsthal (1793-1869), daughter of his elder brother Prince Charles of Hesse-Philippsthal, on 17 February 1812 in Kassel.
From his second marriage he had two children: This article about a member of the German nobility is a stub.