As a toxic material, Lewisite is somewhat interesting, being first reported in a thesis at The Catholic University of America, Washington DC, but being named for Winford Lee Lewis, who read the thesis. Lewisite forms from the reaction of AsCl3 with acetylene.
There was additional chemistry on the episode. Faded writing on a blueprint was recovered. A water-glycerin mixture was applied, and IR light was used.
And good-buy Logan talked to bad-guy Krol, and the CSI team figured out the plan was a heist, not a planned murder of good guy Logan. Good-guy Logan was compromised, as seen in a video, but no explanation was given for the earlier five phone calls.
Memorable line in the episode directed to Horatio: "That's why I own this building and you don't own your cell phone."