Police cordoned off an area of Westgate near Wakefield city centre yesterday while investigations were carried out at the flat at Westgate End.
Insp Carlton Young of West Yorkshire Police said a 41-year-old man was arrested on suspicion of a drugs related offence in Leeds earlier on Sunday.
He said police went to search the man's home address in Westgate End at Wakefield at 4.30pm Sunday when they discovered the chemicals.
An army bomb disposal team from Catterick arrived at the scene just before 9.30pm. Fire crews were also at the scene.
Insp Young said last night: "We are dealing with some unknown chemicals at an address. They (the army bomb disposal team) are there to assist us."
Insp Young added: "This is not being treated as terror related."