I couldn't help linking it up in my mind with a suggestion from the Asimov's board ( www.asimovs.com ) that I discuss languages that occur in really unusual channels, like chemical odor signals and pheromones.
Here's the thing. No matter what kind of language you're proposing that your aliens use (or your humans, if you include sign language), in order for it to appear in a story in English, it has to be rendered in English!
You can always start by describing your language's transmission, and then put the content of messages in English. But if you want the language to feel real, doing a search-and-replace substitution of "emitted" for "said" obviously isn't going to do the trick! That's when you start looking for other places to put information related to language channel.
One possibility would be working with your descriptions, considering how people receiving this communication might respond to it. You could describe emotional response to this alien "speech" in the way you might describe response to scent signals in our world, for example. You could find every scent-imbued word you can think of or look up, and consider ways to integrate them into the dialogue and surrounding text.
All of this is for interaction that occurs in the scent language, internally to that language with "emitters" and "receivers" who can both understand it. But what about contrast, when you have scent communicators and auditory language speakers in the same story, or the same room?
Suddenly now you have to have two versions of English: English rendering of the auditory language, and English rendering of the scent language. How do you construct the dialogue so the two are sufficiently differentiated? Okay, so you design yourself a sophisticated translator which can pick up the scent signals and give a rough rendition of the language in English - what is going to come out of it? The easy solution is to say that your translator is just so darn good that of course it's going to give you the English equivalent of what the aliens say. But as Kelley Eskridge was discussing, translation isn't ever clean; there's no true "English equivalent," and in fact for a language as completely different as this hypothetical pheromone language we're discussing, I struggle to imagine how precise equivalents might be found for anything!
That's when I'd suggest looking into the idea of cultural and linguistic basic concepts for the alien language. The following will be a sequence of speculations, so I hope it makes sense!
In our scent language, very likely individual speaker identity will be hardwired into any "statement", because scent has a long history of being used for marking territory. Then, on top of that, you might have an ambient layer of the emotional state of the speaker as indicated by his or her scent profile. This might be used to correspond linguistically to English things like "definitely" or "maybe" or "!" which indicate the person's level of commitment to the content of the message. Beyond that I guess it might be a question of which chemicals were emitted when and how they were combined to form concepts.
But on the other hand, scent is less flexible than sound as far as temporal variables, because it's basically impossible (outside of a whipping wind) to emit one scent after another without having them mix. So maybe that very mix, that sequential deepening and complication of scent, would be our main variable rather than just a simple question of which chemicals were emitted. Which leads me to wonder how a species using this mode of communication might conceptualize time and change...
This is all totally hypothetical, of course, but it shows some of the ways I go about trying to tease apart cultural and linguistic concepts that I can use when I'm looking for a prose style for an alien language. So to put the final piece on the end for our scent language, maybe this is one where I'd try to have each piece of dialogue consist of a single initial word, followed by sentences of increasing length which would continue to feature this word but add concepts to it on both ends.
Now how the heck would I make that comprehensible by readers? Maybe I'm lucky that I'm not working with this particular scent language at the moment...