Chemo, the mute chemical monster, gains a voice in a story by Len Wein, Curt Swan and Dave Hunt in Superman 370 (April 1982).
The tale opens as Superman decides he just can’t do without a bottle city in the Fortress, even if he has to make a fake, unpopulated one.
Spotting a giant green comet heading towards Earth, he intercepts and smashes it, creating a huge explosion, and paying little to no attention to the part that makes it down to Earth.
The reader, who probably is paying attention, can see that this turns out to be the discorporated Chemo, tossed into space at the end of his last appearance. On his way down to Earth, the comet bit hits an angry man, laid off from his job at a car plant. He had been pestering Lois Lane to write about how evil the company was for firing him.
So when Chemo emerges from the river in his new body, but now talking, and out to destroy the car manufacturer, it’s pretty clear that the two have merged.
Since there is a human consciousness inside the monster this time, Superman cannot just destroy Chemo. Instead he sort of distills him, removing the man, who feels really embarrassed about everything, and then throws him out of the city at super-speed, relying on friction ti burn him up. We see that at least some of Chemo lands in the ocean, where it winds up re-forming in the pages of Crisis on Infinite Earths.
But the story is not quite over, as Superman returns to the Fortress, only to find that his fake Kandor now has real people in it.
This plotline continues in the next issue.