With approximately 150 UV–visible spectra of organic and mineral substances this library is not comparable to other UV–vis spectra databases available. If the number of substances is lesser than other databases, the spectra acquisition conditions and the use of data are exclusively oriented to/for water and wastewater quality monitoring. The great majority of spectra of this library were acquired for substances in aqueous solution, chosen for their potential environmental impact, several of them being a part of the list of priority substances. They are grouped into 10 classes of organic substances, plus one group for organic solvents and one group for minerals. In this new edition, more than 30 substances have been included among 14 pesticides and 15 pharmaceuticals and personal-care products.