After poking around the site, I can't see any specific reference—which makes me suspect it was an independent discovery of a cool idea—but this is very similar to a deliberately-constrained version of the Join Calculus https://www.microsoft.com/en-us/research/wp-content/uploads/... which uses a similar chemical-ish model of computation. There's an implementation of the Join Calculus in an OCaml-like language called (of course) JoCaml. Where Alchemist would write

    2H + O -> H2O

JoCaml would write

    def h() & h() & o() = h2o();;

One of the big differences is that JoCaml allows you to embed payloads inside your atoms, e.g.

    def a(x) & b(b) = c(if b then x else 0);;

will consume an a with an integer payload and a b with a boolean payload, and produce a c with an integer payload. It also lets you include computations as reactions happen, e.g.

    def a(x) = ( Printf.printf "Reacting!\n"; b(x + 1) );;

which lets you use this "chemical soup" model as the basis for concurrent programming.

There is a very detailed tutorial (which appears to have sadly half-broken formatting) which explains JoCaml in more detail here: https://sites.google.com/site/winitzki/tutorial-on-join-calc...