Soon, he discovered teaching, first at the Imperial Lyceum from 1810 onwards, then at the University of Liège from its establishment in 1817, where he taught physics, chemistry, and metallurgy.

His main works focused on pharmacy inspection, the control of suspicious food, and the conducting of toxicological analyses at the request of the Prosecutor's Office.

[3] At the time, in the Principality of Liège, one of the ways to ascend in the enriched bourgeoisie was to associate with the canons, known as trefoiners, of Saint Lambert's Cathedral.

[1] Charles Delvaux, who was interested in the burgeoning industry, hesitated to continue practicing medicine, but in 1810, the door to teaching opened for him.

[5] In 1810, an decree from the Grand Master of the University of France, Louis de Fontanes, entrusted him with the chair of physical sciences at the Imperial Lyceum of Liège.

[1] His zeal and piety, stemming from his religious education and heavily influencing his teaching at the Imperial Lyceum, his conformity, and his loyalty to the regime, earned him a certain esteem from the ruling power in Paris.

[4][5] In 1814, he was appointed by Johann August Sack, the general governor of the Lower Rhine, to teach at the Gymnasium, which replaced the lyceum.

[9] Between 1818 and 1849, he awarded the diploma of pharmacist and, with Nicolas-Gabriel Ansiaux, established a pharmacy course[9] at the Bavaria Hospital in Liège in 1827, which his student, Gilles Peters-Vaust, was in charge of.

Lucie (1812–1883) became a nun of the Daughters of the Cross congregation, Marie-Charles-Adolphe (1815–1887) became a professor of metallurgy at the University of Liège, and Charles-Marie-Joseph (1824–1879) became a doctor of medicine and mayor of Chevetogne.

This mainly involved pharmacy inspection, the control of suspicious food, and the conducting of toxicological analyses at the request of the Prosecutor's Office.

[9] His analyses of the waters of Chaudfontaine, the Sainte-Catherine fountain in Huy, the coal mines of Sainte-Marguerite and Sainte-Walburge in Liège, Basse-Wez in Grivegnée, and Juslenville were published by Richard Courtois and Toussaint-Dieudonné Sauveur.

[9] As a chemist, Charles Delvaux determined the composition of a species of ferric phosphate found in the spoil heaps of a lead mine in Berneau.

[9] The geologist André Hubert Dumont found another specimen in a quarry in the same locality, which he presented to the Geological Society of France on May 21, 1838.