 The French expertise in explosives was well judged by the Allies when later they dispatched Jöns Jacob Berzelius to Paris to update general knowledge.In 1819 he spent two full months as a guest of Berthollet in the laboratory at Arcueil experimenting, but above all sounding Pierre Dulong whose memoir on a new detonating substance (nitrogen trichloride) had appeared in the 1817 volume of" "Mémoires de Physique et de Chimie de la Société d'Arcueil"" (André-Marie Ampère had already briefed Humphry Davy on prior stages (1811-1813) of Dulong's invention).There were three volumes of ""Mémoires de Physique et de Chimie de la Société d'Arcueil""