Chemical Abstracts Service Registry Number (CAS RN) is a unique number tagged to a chemical by the American Chemical Society and is used internationally to identify chemicals. You may refer to the official website of the European Union for assistance. Do note that the Europa website is meant as a guide and traders are advised to make reference to the Singapore Trade Classification, Customs and Excise Duties (STCCED) publication for the 8-digit HS code. Alternatively, you may wish to conduct your personal research on the chemical structure and its functionality to determine the most appropriate HS code.