# Free chemical database to search for physical properties?

I am looking for an Open-access tool that can search "backwards", eg. give me all the structures corresponding to a given heat of formation, critical pressure, etc. It would be even better if the database canbe automatically searched by API or by downloading it. Currently my best go is ChemExper, where I can search for some of the properties, but it is challenging to make it automatic. Is there anything similar in the field?

As I've mentioned on other related questions, this is very much an open topic. There aren't many open-access databases in chemistry, and far fewer that have APIs.

• As suggested in the other answer, there are multiple ways to query / scrape Wikipedia.
• ChemSpider offers some property search features.
• Reaxys offers some property searching, including spectra features. It's not open access.
• Indeed, what I see is open access chemistry databases have a long way to go. The reason I asked this question is exactly this: there might be some databases that slipped my knowledge. On an open forum like stackechange, there might be someone who knows something. – Ezze Feb 23 '16 at 17:45
• @Ezze I think it's a good question. It's just not that different from the last question – Geoff Hutchison Feb 23 '16 at 19:02
• Yes, you are right. I didn't see the question. However, I am hoping for a better answer this time. – Ezze Feb 23 '16 at 19:04
• @Ezze - Nothing has changed since then. In a few months, we'll be rolling out API-based property search for PQR but these would be computed values. – Geoff Hutchison Feb 23 '16 at 19:05

You might search the German Wikipedia using SPARQL via DBpedia.

Go to http://de.dbpedia.org/sparql and run your query, e.g.

PREFIX dbo:<http://dbpedia.org/ontology/>

SELECT ?chem ?bp
{
?chem a dbo:ChemicalSubstance .
?chem dbo:boilingPoint ?bp .
FILTER ((?bp >= 372) && (?bp <= 374))
}
ORDER BY ?bp


I've just discovered this website where you can find a tremendous amount of data, especially about inorganic chemistry with things like E-pH diagrams, phase-diagrams, things about alloys of different metals, ultra pure silicone, salts, elements, nuclear data and so on.

And if you prefer sugar derivatives here is a great database with online calculators about many sugar things, syrops etc.

Enjoy !!!