Jonathan Norling, 22, was arrested after he turned the poisonous chemical over to police, the New York Daily News reported Thursday.
He told police another chemical agent, Abrin, which is similar to ricin, was in his apartment.
A raid on his apartment Wednesday yielded an unknown substance police said.
The substance was not immediately identified.
Police tested the air in the apartment for noxious chemicals and took his wife, infant daughter and a friend in the flat to a hospital for observation.
Norling brought in the cyanide Friday, police said, but he only recently admitted to having more toxic chemicals. He was taken to a psychiatric hospital for evaluation.
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