Way back when, I threw together an app called Green Solvents, which got started anachronistically from a tweet by Sean Ekins (which I misinterpreted, but it got the conversation started, so all is well). Since mid-2011, the app hasn’t had much attention, but that has now changed: it has been rewritten and given a much more modern look. The overhauled version is live on the iTunes AppStore, and is free to anyone with an iThing.

The basic premise of the app is that the American Chemical Society Green Chemistry Institute Pharmaceutical Roundtable (trying saying that in one breath) put a lot of time and money into producing a solvent selection guide, but at the time the distribution method consisted of a PDF file that was locked behind a firewall that required a membership login to access, even though it was nominally freely available. We decided to fix that by keying in the information in a more informatically friendly format, and pushing it out as an app, in the hope that people would be more inclined to actually use the information.

A year later, I had been dabbling with building a parallel suite of apps for the Android platform, and built the Lab Solvents app. This had a bit more attention given to the user interface, and additional solvents, some of them pulled from the GlaxoSmithKline Solvent Selection Guide: where they overlapped with the ACS ratings, the numbers were averaged. And all this was later published in ACS Sustainable Chemistry and Engineering (the very first issue, almost the first article: page 8).

Back to the iOS app: the app was and is rather simple, so it was not a huge amount of effort to rewrite it using Apple’s more modern programming tools (i.e. Swift rather than Objective-C), using a the set of core libraries that began with the PolyPharma app and XMDS beta. Some attention was paid to the idea of being able to reuse the basic “gallery” style user interface for other projects, rather than being a one-off. And as you can see from the screen capture, the visual display is a lot more modern and pleasant than the relatively crude original:

Rather than explicitly dividing into sections, there are buttons along the top that correspond to categories. Assuming that you have a background in chemistry, you should be able to work these out. Turning each of them on or off makes it act like a filter. There are also some summary nasties: the three buttons on the right (flame, skull & crossbones, and dead fish) are a summary of the 7 different environmental properties assigned to the solvents. They are used on the solvent glyphs themselves along with a colour code, to give you a rough idea at a glance which ones are particularly unpleasant. Tapping on the corresponding buttons along the top panel causes the solvents to be sorted by nice first, nasty last; so if you want to know which solvents are most green in every sense, turn them all on. Spoiler alert: the only solvents that are completely green are water and carbon dioxide. If we could do all of our reactions in either of these solvents, the whole green solvents concept wouldn’t be a thing.

The primary deliverable of the app is still about as simple as it gets: tapping on a solvent brings up a detail view, with all of the specifics shown:

The specific environmental categories are shown listed out, and below them a variety of useful reference information. CAS registry numbers are given for each solvent, along with handy links to ChemSpider, PubChem and CompTox. Experimental physical properties of most relevance – melting & boiling points and density – are also included.

So if you have any interest in picking better solvents, and have an iPhone or iPad, head on over to the AppStore and grab this app. Keeping in mind of course that these data are guidelines, but the ratings do represent an awful lot of expertise.