Editor Q&A: The Merck Index* Online

Mark Archibald, Data Content Editor explains what The Merck Index Online offers and why it is one of the most authoritative and reliable sources of information on chemicals, drugs and biologicals.

Tell us more about The Merck Index Online

The Merck Index Online is an encyclopaedic database of chemical substances – an evolution of the printed reference work The Merck Index. While the content has a focus on chemicals and biologicals of pharmaceutical relevance, the database’s scope encompasses all of chemistry, from inorganics and materials to peptides and proteins.

Who would find the database useful?

Of course the primary users are chemists, particularly those with interests related to pharmaceuticals. Users of The Merck Index Online also include researchers in related fields such as biochemists, pharmacists and toxicologists, as well as information professionals and those working for government agencies. In fact, the highly curated nature of the entries means they can be particularly useful to researchers looking at topics only tangentially related to their fields – topics in which they aren’t experts.

It’s also used by students and teachers at various levels of chemical education.

What features are included?

Each entry, called a monograph, typically relates to a single chemical compound or substance. It begins with the chemical structure alongside related information such as molecular weight and formula, trivial and systematic chemical names, and other identifiers including CAS numbers. The main body of the monograph lists chemical and physical properties drawn from primary literature, followed by a description of the substance with references to key literature and patents.

One of the main advantages of being online is that the database is fully searchable – by chemical name or other identifier, by chemical and physical properties, and by chemical structure. The indexes from the print editions, such as the therapeutic category index, have been incorporated as searchable fields. All of these types of searches can be combined into a single query.

Why is The Merck Index Online an important tool for chemists?

I think the key point is to understand how it complements other resources. There are many valuable research tools, but none of them can claim to be suitable for every purpose. The Merck Index Online comes into its own when an overview of a chemical substance is required. If a researcher wants to find everything published on a particular molecule and sort through the results themself, then a comprehensive database like SciFinder or Web of Science is an obvious choice. What The Merck Index Online offers is a curated selection of the most important and relevant references, in many cases chosen from thousands of search results.

How does the information contained in The Merck Index Online compare to free resources such as ChemSpider and Wikipedia?

Again, complementarity is key. ChemSpider is far larger, containing 45 million compounds compared to about 20,000 in The Merck Index Online. However, it’s logistically impossible for a resource of this size to be curated to anything like the same extent as The Merck Index Online. ChemSpider aims to aggregate as many data values, references, links to other sources, etc. as possible, while The Merck Index Online aims to provide a more-or-less self-contained description of the compound and only the most reliable data values and most relevant references.

The relationship with Wikipedia is a little more complicated. For particularly well-known compounds like cholesterol or aspirin, the Wikipedia pages will have had a great deal of contributions and editing and often end up being more detailed than the corresponding entry in The Merck Index Online. Further down the scale, such as for drug compounds that are important but don’t have the same level of visibility, the situation often reverses and the Wikipedia entry is very brief, while The Merck Index Online will have a detailed description. Likewise, the extent and reliability of included chemical data in Wikipedia will tend to scale with the amount of attention the page has received, whereas the data in every entry in The Merck Index Online has been carefully checked.

It’s important to emphasise that both ChemSpider and Wikipedia are valuable resources – they just have different strengths to The Merck Index Online.

Can you tell us about your role as an editor of the database and why it is important?

The central part of my job is to write new content. This starts with choosing a chemical substance to write about – unlike a comprehensive database, where any known compound is a candidate for inclusion, The Merck Index Online’s limited size means that we select compounds with important applications or particular academic interest. In practice that means approved drugs, widely used lab reagents and catalysts, agrochemicals, materials involved in renewable energy technology, and so on.

Once a substance has been chosen, I go through much the same process as a researcher would when investigating a new topic – searching for relevant literature and patents and then sifting through the results to find the most important papers. For chemical and physical data, I try to find every published value to see if there is a consensus, and if not investigate to determine the most reliable value. On occasions where this isn’t possible, I’ll include and reference multiple values to illustrate the uncertainty in the literature.

The importance of the editors can be summed up in one word: curation. The volume of available scientific articles and data is constantly increasing and can at times be overwhelming. Highly curated databases like The Merck Index Online give researchers a shortcut to the most important and reliable information.

Want to find out more about The Merck Index Online?

Watch our introductory video to find out more about the database.