First published in Galaxy. Caveat: I will "ruin" some of these Larry Niven stories as it is impossible to discuss the science without revealing the key plot points.
Mars explorers find they weren't the first. The prior inhabitants appear to have adapted to the acidic environment. When they find something that looks like a well, it turns out to be used for the exact opposite purpose. The explorers add water to a corpse they found:
"That nitric acid wasn't dilute, exactly, but there was water in it. Maybe this guy's chemistry can extract the water from nitric acid."What they'd achieve is not clear-- However, the corpse explodes. Remember, kids: "Add acid to watuh, as you oughta." Assuming this is the reaction intended. Below is a video of a kid pouring water into acid (out to prove his chemistry professor wrong). The mixture only heats up (in his other video he does not measure before and after, nor account for different volumes, nor the fact that the water he adds has not been in the sun). As an undergraduate, I've had the mixture fizz and splatter acid out.
Niven may have had another reaction in mind although the corpse is dry, so when heated, maybe it becomes kindling.