This document discusses ChemSpider, a database of small organic molecules, as one of the pillars of a semantic web for chemistry. It provides an overview of ChemSpider's capabilities, including its large database containing properties, names, and spectra of molecules. Users can contribute new data or curate existing data through an easy deposition system. ChemSpider also functions as a search engine for chemistry, allowing users to search and navigate relationships between molecules. The system utilizes extensive computing infrastructure and standardized interfaces like APIs. It is presented as an example of a federated semantic web system for chemistry that incorporates data from multiple sources using open standards.