Final answer:
Cyanide complexes with thiosulfate in the second step of its poisoning treatment to form thiosulfate ions, which are excreted in the urine.
Step-by-step explanation:
In the second step of cyanide poisoning treatment, cyanide complexes with thiosulfate to form thiosulfate ions. Thiosulfate ions are then excreted in the urine. This process is known as conjugation reaction and is facilitated by an enzyme called 'rhodanase'.