Interesting ... the most cited chemistry papers are seminal works on graphene. You'd think we be getting more kids on these forums asking about graphene. We get some, but not as many as I'd expect if it were as hot a topic.
I remember back in my day, one paper was cited every time. The original Lowery assay for protein :
http://en.wikipedia.org/wiki/Lowry_protein_assay Do check out the Wikipedia page, it is listed in the references as the most cited paper in publishing history. I actually had to go see my university's copy. The bound collections of that journal were old looking, like all documents that are that old, except for that paper. It was much yellower, and even stained and notes written on. I guess, in 60 years, a lot can happen to an article.