Nomenclature & identification
The nomenclature used in marine transport can be unclear some substances being transported under various synonyms of their correct chemical names. However the IMDG and IBC code names should always be used for the marine transport of chemicals.
Besides using the correct name for the product, it is very important not to have any misspellings or misnaming when discussing chemicals, many common chemicals having very similar names even to the extent of differing by one letter. For instance,
Sodium chloride is not classified as hazardous while sodium chlorite is classified as corrosive and oxidizing. Again, calcium carbonate is not classified as hazardous while calcium carbide reacts with water to form acetylene.
The CAS registry number (or CAS nr.) is uniquely assigned to each compound in the chemical literature. This is a three-group number, of which the first group can have up to 7 digits, while the second group is always 2 digits and the third is a single ‘check digit’ calculated from the first digits.
CAS numbers are assigned by the Chemical Abstracts Service to facilitate database searches. Currently almost all molecule databases can be searched by CAS number reference.
An identification system more specific for dangerous goods is the UN number (or UN ID). This is a four-digit number assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods.
UN numbers are assigned on the basis of hazard rather than on name. This means that some substances have individual UN numbers while substances that have similar properties may receive a common UN number. Substances with different levels of purity or concentrations can also receive different UN numbers.
Some examples of UN numbers are shown below.
Table 10 Examples of UN numbers
| UN1993 | Flammable liquid, not otherwise specified |
| UN1830 | Sulphuric acid with more than 51 percent acid |
| UN1831 | Sulphuric acid, fuming with 30 percent or more free sulphur trioxide
or Sulphuric acid, fuming with less than 30 percent free sulphur trioxide |
