I went down a bit of a rabbit hole with this yesterday. It's interesting--there's clearly some parts of the poem that are effective and lasting, while other parts aren't.

"thought was H20 was H2SO4" is identical in all the variants I found after the mid-20th-century. Most, but not all, have "What he thought was H20 was H2SO4". It seems like they "perfected" that part and it hasn't really changed since.

But the rest is very changeable--a few variants mention chemists and most mention a male name of some sort, but most have nothing else in common.