Arsenic compounds have been used historically as pigments, and as components of bronze.

Dwarf Fortress includes a variety of different types of bronze, and already includes Orpiment and Realgar (two common arsenic ores) as valid stone materials, why not make arsenic bronze, and arsenic dyes? Such uses of the material predate the 1400s, and were used well into antiquity.

This mod does the following:
-Makes Orpiment and Realgar ores of Arsenic
-Makes new metals: Arsenic, and Arsenic Bronze
-Adds a reaction to make Arsenic Bronze
-Makes Arsenic Bronze a permissible reaction for dwarven civilizations

Future plans:
-Make Orpiment and Realgar valid options to be used as dyes.

Changelog:
-0.03:
Made Arsenic Bronze a permissible reaction for "Mountain Entity" (Dwarven civilizations), allowing Arsenic Bronze to be crafted at smelters


Feel free to post any issues with the mod here:
https://www.bay12forums.com/smf/index.php?PHPSESSID=82gna2ee8gt7ot535a9o2ihc1n&topic=183617.0