The use of coal tar colors in food products
A 1904 New York treatise by Hugo Lieber, issued by H. Lieber & Co., on coal tar dyes used to colour foods and their physiological effects, aimed at chemists and food inspectors. The two pictures are chemical structural diagrams: a triphenylmethane dye with sulfonate groups drawn as a branched ring-and-bond formula, and an azo compound with a naphthalene ring labelled with alpha and beta positions. A designer might take their clean line-drawn molecular geometry as a model for scientific diagrams.
