Consider the following premises. p_8 <-> q. p_8 <-> q. Can we infer ~(q <-> p_8) from them?
 From p_8 <-> q we can infer p_8 -> q. From p_8 <-> q we can infer q -> p_8. Finally, from q -> p_8, p_8 -> q we can infer q <-> p_8, which contradicts ~(q <-> p_8). Therefore, the answer is no.