When a site has a question that could benefit from the expertise on another SE site, it makes sense to go to that other site's meta or chat and ask for help. For example, the Bicycles site had a question a while back that could have benefitted from some people who had some physics chops.
We now have a question that could benefit from some knowledge in chemistry. (The question may or may not be closed as a duplicate, but that's another issue.) However, there's no chemistry site (yet).
Leaving aside the question of whether it would do any good: Would it be considered good form to post to the Chemistry proposal and ask for help?
Edit, in case I'm not being clear: I'm not suggesting one would go to the Area 51 proposal and ask "Hey, how is vegetable oil different chemically from chain lube?" I'm suggesting it would make sense to go there and simply post a link to the existing question: "We have a question about chemistry and lubrication, folks here might be interested in helping out."