A CAS number is a numerical designation assigned to chemical substances by the U.S. Chemical Abstracts Service (CAS). Each individual number enables the unequivocal identification of a substance. It is one of the most common methods used in the world.
The Chemical Abstracts Service is a department of the American Chemical Society and it maintains a database of chemical compounds and sequences. At the moment, the CAS database contains over 55 million different chemical compounds, both inorganic and organic. Every entry to the CAS database is identified based on the CAS register, or CAS number for short.
Formerly chemical substances were identified mainly by means of a wide range of synonyms. However, they often proved to be unclear, as the names were constructed following local conventions, which referred to the structure, origin or chemical formula. That is why some of the well-known substances may bear numerous historical, generic or commercial names.
CAS numbers were created with simplicity and regularity in mind, so that they are easily searchable in databases. It is a reliable, international designation assigned to the specific substance in different nomenclatures and disciplines, approved by the sciences, industry and regulatory bodies.
The format of CAS numbers is as follows: xxxxxxx-yy-z and may contain up to 10 digits. These are three digit sequences separated by hyphens. The first sequence can range from two to seven digits, the second one always has only two digits, and the third sequence comprises of a single digit.
The last digit is known as the control sum, which is a digit obtained following a special algorithm, ensuring data integrity. In the case of the CAS number, the control sum is obtained by summing the product of the first digit multiplied by 1, the second to last digit multiplied by 2, the third to last digit multiplied by 3 etc. (depending on the number of digits in the designation). From that sum, the modulo 10 is determined thus obtaining the final CAS number digit.
We can see this by using water as an example, whose CAS number is: 7732-18-5.
The first and second segment of the CAS number do not have any special meaning. They increase with the addition of subsequent substances to the register.
A CAS number is assigned to chemical compounds for the purpose of their identification. However, it should be remembered that it is just a designation, and not the product’s unique character. An example of this is the different anhydrous forms of citric acid, which are labelled with the same CAS number, although compounds with different hydration levels can feature other numbers. The assigned number may also aid in distinguishing stereoisomers of the given compound. Glucose has two forms: L-glucose and D-glucose (dextrose). L-glucose, with CAS number 921-60-8, is a mirror reflection of D-glucose, with the CAS number 50-99-7.
CAS number is one of the most popular methods of searching substances. With the use of this designation, one can be certain what the chemical compound in question is. Free databases are available, where via the CAS number the name, structure or molecular formula of the given substance can be found, or vice versa.
The products in the PCC Group’s portfolio also have CAS numbers assigned to the chemicals they contain. Therefore, in order to meet the demand expressed by the customers, the Product Portal has been adapted to the functionality of a CAS number browser. A specialised database has been created, containing the numbers assigned to all the products. Each of them contains the basic information about a chemical compound. It is also possible to view the structural and molecular formula. Thanks to the CAS number browser, PCC Group customers can easily find the chemical substances that meet their requirements.