Chemical CAS number: All you need to know

Chemical CAS numbers are unique identifiers assigned to a particular chemical and are crucial for researchers working in a laboratory setting. They allow chemists to identify, differentiate, and track chemical compounds easily and are also essential for regulatory compliance.

CAS numbers have become increasingly important in the pharmaceutical intermediates, food, and industrial sectors, and understanding them is an important part of ensuring safety and accuracy in any chemical analysis. So, let’s dive into exactly what chemical CAS numbers are and why they matter.

What is a CAS Number?

A CAS Number (Chemical Abstracts Service registry number) is an internationally recognized identifier for chemical substances, including proteins and polymers. It stands for Chemical Abstracts Service registry number and has been created by the American Chemical Society (ACS).

cas number format

The CAS Number helps scientists accurately identify chemical substances and quickly locate important information about them. It is made up of three parts: a unique seven-digit numerical code that identifies the substance, followed by two letters indicating the source of the data. Other than in academic research, industry professionals also use this system to find information on chemicals they may be using in their products or processes.

What is a CAS number used for?

A CAS number (Chemical Abstracts Service Registry Number) is a unique numerical identifier the American Chemical Society assigns to certain chemicals. It’s used to classify and identify chemical substances, helping scientists, manufacturers, and suppliers track them. For example, if a pharmaceutical company produces a new drug, it can use its associated CAS number to find out what it’s made up of quickly.

A CAS number also helps people in hazardous environments avoid mixing incompatible chemicals or handling dangerous compounds without the correct safety equipment. CAS numbers are helpful for properly labeling and tracking materials throughout their life cycles from production to disposal.

Why is the CAS number important?

cas number
CAS number

The CAS number is an essential tool in science and industry. A unique numerical identifier assigned to every chemical substance or mixture helps chemists and other professionals identify, classify and track them properly. 

The main purpose of the CAS number is to provide a clear standard for scientists, researchers and regulators when dealing with chemicals and substances. Most substances have different common names depending on where they are used. One uniform identifier makes it easier to refer to any material in scientific literature, public safety regulation compliance documents, databases, etc. 

In addition to help identifying and tracking materials, CAS numbers can be used to access detailed information about their properties such as solubility, boiling point, melting point, toxicity levels, stability data and much more. This allows chemists to know what they’re dealing with before they start working with it and to compare different materials quickly and easily. 

Furthermore, due to its importance in helping ensure safety regulations are followed, individual batches of chemicals can often need special handling procedures dependent on their exact components – which can be tracked through their corresponding CAS numbers. 

How is a CAS number assigned to chemicals?

A CAS number, or a Chemical Abstracts Service Registry Number, is assigned by the American Chemical Society (ACS) to identify chemical substances uniquely. The CAS number is a numerical identifier that enables scientists and chemical suppliers to quickly find safety, regulatory and other relevant information about a specific substance. 

To assign a CAS number, an applicant must submit a sample of the pure material and detailed technical literature surrounding the new material. After ACS receives this information, it processes the application for accuracy and completion before assigning a unique identifier for the substance. This process may take several weeks or months because of its complexity and thoroughness. Once assigned, the CAS number will not change regardless of where or how it is referenced in the scientific literature or by suppliers worldwide.

What is the CAS number in chemistry?

The CAS number is a unique numerical identifier assigned to every chemical substance described in the open scientific literature. It is composed of three sets of numbers separated by hyphens and functions like a social security number for chemicals – it serves as a “fingerprint” that uniquely identifies them from one another.

The first two parts of the CAS number identify the specific chemical compound, while the third part indicates how many variations exist for each compound—the greater the number of variations, the higher this third part will be. For example, water has a CAS number of 7732-18-5; 7732 is the first set of numbers to describe water itself and 18 is its variation value.

How do I find a CAS number for a chemical?

Finding the CAS (Chemical Abstracts Service) number for a chemical you are researching or using can be challenging. Fortunately, there are several solutions to help you find it.

The first place to start is with the American Chemical Society’s CAS website. You can type in the name of the chemical you’re interested in, and it will provide you with its CAS number. You can also type in the formula or molecular structure of the chemical if that is known.  

Another great resource is PubChem, which is run by the National Library of Medicine and part of their broader NCBI database. PubChem provides an extensive list of chemicals and unique CAS numbers. It also contains more detailed information about each chemical that may be available from other sources. 

You can also check Ullmann’s Encyclopedia of Industrial Chemistry and The Merck Index for more detailed information on specific chemicals including their CAS numbers. Chemical manufacturers should also be able to provide this information if necessary. 

It’s important to note that multiple chemicals can share the same CAS number due to synonyms for a particular substance being registered under one single reference number. If unsure whether or not you have found an accurate match, always double-check your results with another source before proceeding with any further research or experiments involving that chemical. 


The CAS number is critical to identifying a chemical and its properties. Knowing the CAS number of a chemical can help companies and researchers determine the safety of a chemical, as well as its sources, uses, and potential hazards. By understanding the importance of the CAS number, companies can ensure that their products remain safe for consumers, and researchers can ensure that their chemicals are properly tracked and accounted for.

Maria Zhang

Maria Zhang

Maria Zhang, an experienced chemical industrial expert with more than 10 years of experience. She has worked with a range of industries, from large-scale manufacturing and research to smaller-scale projects. With her expertise, you can learn differently chemical knowledge!

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