How many chemicals are listed by CAS?

• A. 11 million
• B. 1.13 million
• C. 113 million
• D. 113 thousand

Answer: (C)

The main idea here is how many distinct chemical substances CAS has registered. CAS assigns a unique registry number to every distinct substance, and the count you see is the number of registry records, not the number of possible formulas or names.

The CAS Registry is immense, including small molecules, polymers, inorganic compounds, solvents, formulations, and mixtures. It has grown for decades as new substances are identified and documented, and the size is on the order of hundreds of millions of records. A commonly cited figure is about 113 million registered substances, which best matches the given options.

So, 113 million reflects the large, ongoing catalog of substances that CAS maintains. The other numbers are far too small to represent the registry’s scope.