This is a short story I read in school in the '70s in an anthology.
People had to wear protective suits, and if these were torn, the person inside would dissolve. The protagonist's suit gets torn and he stops to smoke a cigarette. He then realizes that the nicotine makes you immune and runs off screaming.
I am pretty sure the story is The Last Objective by Paul Carter , 1946, by Street & Smith Publications, Inc. Published in Astounding Science-Fiction.
It was dramatized in by the radio show Dimension X, which is where I first heard it : https://tangentonline.com/oldtimeradio/dimension-x-qthe-last-objectiveq-by-paul-a-carter/
I also have the story in an anthology book : A Treasury of Science Fiction , 1980 Bonanza Books , edited by Groff Conklin
here are some quotes that support the biological weapon dissolving people:
And then Lieutenant Carpenter screamed.
All eyes were riveted on the psycho officer, a hideous suspicion growing in their minds as he cringed in a corner and yelled meaninglessly, his whole body shaking with unutterable terror. They had all seen men afraid of death-but in Carpenter's mad eyes was reflected the essence of all the hells conceived in the ancient religions he slavered, he whimpered, and suddenly his body began to ripple.
His fellow officers stood rooted to the deck in sheer fright as he slid rather than fell into a huddled heap that continued to sink down after he had fallen, spreading and flowing and finally running like water. Sanderson stared in stunned horror at a pool of sticky yellow fluid that dripped through a bronze grating in the floor.
"Read that radiogram again," he ordered hoarsely, signaling to the two crewmen to release their prisoner. The exec rubbed his wrists to restore circulation as the handcuffs were removed. Then he picked up the crumpled paper, smoothed it out. "Research Project X-39, a semi-living chemical process attacking all forms of protoplasm, was released-" Culver choked over the words.
And then in a few terrible minutes of screams and curses and hideous dissolution, all the officers understood why the Asiatics had committed suicide."
The only survivor is Carson who is a synthetic soldier who smokes:
Carson, the strange one-separated by more than aloofness from his fellows-spawned in a laboratory, the culmination of thousands of experiments in the vain hope of circumventing the extremity of the slaughter by manufacturing men. His metabolism was subtly different from that of normal man; he needed nicotine in his system for some reason that was why he chain-smoked-but tobacco was a narcotic. It could not protect protoplasm. Why can't you die, Carson? All through the ship, silence, wet clothing, little pools - not even the dead had escaped - nothing moved or lived except this running, half-mad man or Thing-born in a laboratory, if one could say he had been "born"
A quick movement of his gloved hands sealed the round helmet on his shoulders. He ran and stumbled and climbed through passageway and down ladders; he fairly flew down the landing ramp and soon disappeared in the black depths of the tunnel.
