Chemisches Zentralblatt was an old publication that was a lot like a big catalog of all the research and information that was available about chemistry. It contained summaries and references to different articles, books and experiments about chemicals and their properties. Think of it like a big library where scientists can go and check out books and papers about chemistry. It was like an encyclopedia that helped chemists keep up-to-date with what was going on in their field. Nowadays, there are digital versions of Chemisches Zentralblatt available online that scientists can use to find the information they need.