At the Silesia Verein Chemischer Fabriken in Saarau (Lower Silesia), Eugen de Haën became involved in 1860 in the chemical laboratory of Julius Knoevenagel (1832 – 1914) in Linden near Hanover, with whom he initially founded the small Chemische Fabrik Dr. Eugen de Haen & Cie in 1861. at Falkenstrasse 9.

[3] In 1861, he founded the E. de Haën company in Linden and later in List, two small villages close to Hanover.

Therefore, the company had to look for a new location and finally found one at a favorable price in a 120-acre site with good rail connections in the village of Seelze.

The old company site was transferred to the descendants in the course of the early succession and was finally demolished at the expense of the heirs.

[4] All development costs for the future building land contractually concerned the heirs, and the "construction of an ornamental and playground" was therefore dedicated to the benefactor as de Haën Square.