Like many chemistry-using characters, it involves the writer having some knowledge about chemistry, so don't expect to see him too often.

I mean, the Legion had Chemical King, who could speed up or slow down chemical reactions. He joined the team the same time as Timber Wolf, who was basically a superhero werewolf at the time, but sounds a helluva lot easier to write. Anyway, today we've got Chemistro, from 1990's Iron Man #252, "Apothecary Now!" Written by Dwayne McDuffie, pencils by Herb Trimpe, inks by Al Milgrom.

This was the third Acts of Vengeance crossover issue, although counting #250 with Doctor Doom in the future seems like a stretch. And, Tony had faced Doom before, anyway. #251 had featured the Wrecker, and right on the heels of that fight comes another foe Tony hadn't faced before: Chemistro. Or, more accurately, Chemistro II: Calvin Carr, who had stolen his brother Curtis's invention, with help from the Wizard. Curtis had lost a foot to his "alchemy gun," and thought his brother was an idiot for messing with it.

Tony gets his armor turned into lead, but Curtis distracts Chemistro enough for Rhodey to help Tony get out of the suit: the armor isn't really all that thick, although I'm surprised it held up long under its own weight. Left in his underwear, Tony's able to get a pretty girl in a convertible to stop and give them a lift. Back at Stark Enterprises, Tony tells Curtis they will rebuild the Stark Prosthetics research center that was destroyed by the Wrecker, and they begin work on a counter to Chemistro's weapon. The force-field they build gives Iron Man a little edge against Chemistro, who does wreck a lot of Stark Industries buildings and equipment. Chemistro manages to trap Tony in water, by then turning it to steel; but Tony tries to heat the steel to accelerate its decay. (The elements created or changed by Chemistro's weapon were always unstable, and would dissolve into dust in time.)

Curtis confronts his brother again, and gets his other foot shot off for his trouble. That gives Tony time enough to get free, and he takes down Chemistro with judicial application of his tractor beam, crushing his weapon and possibly his hands. Later, Curtis vows he will stand on his own feet again, even if he has to build those feet himself. Sometime later, Curtis would build a suit of armor called High-Tech, which may have been McDuffie's precursor to Milestone's Hardware!