On his return to New York, in 1848, he established with Charles T. Harris a laboratory on Broadway for the purpose of giving instruction in analytical chemistry, and for making commercial analyses.

Doremus was authorized by the French minister of war to modify the machinery in the Bouchet pouderie so that gunpowder of the American character could be produced.

Subsequently, an exhibition of the firing of compressed granulated powder in cannon and small arms was made in Vincennes, before Napoleon III and many of his generals.

This system was adopted by the French government, and a large portion of the Mont Cenis Tunnel was blasted with "la poudre comprimée."

He established a special toxicological laboratory, with a dissecting room attached, kept under lock and key, using only reagents of known purity, and purchasing new glass and porcelain vessels for each case.

Under his direction, specially prepared vessels for the generation of this powerful gas were introduced between decks, the hatches battened down, and the vapor allowed to accomplish its work of destroying germs.

He obtained aid from the Board of Health in suppressing the gases emanating from the gas houses, and opposed its action in adopting the "lactometer with the senses" as the sole means of testing the purity of milk.

His published writings include only a few addresses, notably that at the unveiling of the Humboldt statue in Central Park, and papers delivered before scientific societies.