ChemSpider - free database in which data on properties more than 58 million chemicals, mainly, organic chemicals are collected.
ChemSpider - the structural database. As envisioned by creators, the structure of chemical is primary identifier in construction of all information array; all remaining identifiers (the name, registration numbers etc.) are read secondary here and therefore not always precisely correspond to a certain chemical object.
Example of discrepancy to which we not always pay attention. The term "table salt" is not only trivial name of substance of chloride of sodium, but also the name of goods in which the substance Na Cl is the basic - but not the only thing - a component.
Data in ChemSpider accumulates from different sources: from other databases (484 for 2017) - big and small, scientific and educational, commercial and free, - and also from primary literature - and reviewed, and not undergone reviewing. As a result of data on substance represent rather a compilation of earlier published information here, but not an array of the adjusted numerical data.
Strength of ChemSpider - a search capability of information on the given structure of substance.
Reference to a resource: http://www.chemspider.com