I worked on aircraft in the 1960s and there were no chemicals in the condensate trails.
One person did point out to me that there was a trail AHEAD of the aircraft that looked like a sight blue streak. He said it was from the nose radar. On the ground, I’ve seen that blue streak ahead of quite a few aircraft.
FROM the ground, I’ve seen that blue streak.
A company in Waco, Texas modifies large passenger planes. It is a fact that they install a long radio antennae “wire” that is uncoiled from the rear of the plane once it’s in flight. Some people I know who worked there told me it’s almost a mile long.