When you go see the first friend, you can say upfront something like "I came over because I am free for an hour." Then, when the hour is up, comment on that and then get up to leave."

Mentioning suicide is a big concern though. Perhaps you could encourage him to speak more about that? You could ask what his reasons to die are, what his reasons to live are, and ask if he has a plan and the means needed to implement the plan. If what he says still is concerning, I suggest that you call 1-800-273-TALK (8255), the National Suicide Lifeline, and ask them for advice on what to do next. For one thing, you could encourage him to call that number.