Two chemists walked into a bar. *corny chemistry joke* The first chemist said ""I'll have H20."" So he drinks his H20 and feels fine. The second chemist said ""I'll have H20 2."" He dies. He couldn't handle the Hydrogen Peroxide.

Two chemists walk into a bar. The first chemist says ""I'd like a glass of H2O"". So the bartender gives him a glass of water. The second chemist says "" I'd like a glass of H2O too"". So the bartender hands the second chemist a glass of water also, as no bar serves it's customers hydrogen peroxide.

Two chemists walk into a bar. The first chemist says ""I'd like a glass of H2O."" So the bartender gives him water. The second chemist says ""I'd like a glass of H2O too."" So the bartender also gives him water, because he knows what he meant and had no conceivable reason to be carrying hydrogen peroxide, much less to be giving it as a drink.

Two chemists walk into a bar The first chemist tells the bartender "I'll have some H2O, please." The second chemist agrees: "I'll have some H2O also, please." The second chemist died of aluminum, sulfur, and oxygen poisoning.