1.1.1.: Numbering of entries and identification of a substance Index numbers
Entries in Part 3 are listed according to the atomic number of the element most characteristic of the properties of the substance. Organic substances, because of their variety, have been placed in classes. The Index number for each substance is in the form of a digit sequence of the type ABC-RST-VW-Y. ABC corresponds to the atomic number of the most characteristic element or the most characteristic organic group in the molecule. RST is the consecutive number of the substance in the series ABC. VW denotes the form in which the substance is produced or placed on the market. Y is the check-digit calculated in accordance with the 10-digit ISBN method. This number is indicated in the column entitled ‘Index No’. EC numbers

The EC number, i.e. EINECS, ELINCS or NLP, is the official number of the substance within the European Union. The EINECS number can be obtained from the European Inventory of Existing Commercial Chemical Substance (EINECS) ( 16 ). The ELINCS number can be obtained from the European List of Notified Substances (as amended) (EUR 22543 EN, Office for Official Publications of the European Communities, 2006, ISSN 1018-5593). The NLP number can be obtained from the list of ‘No-longer-polymers’ (as amended) (Document, Office for Official Publications of the European Communities, 1997, ISBN 92-827-8995-0). The EC number is a seven-digit system of the type XXX-XXX-X which starts at 200-001-8 (EINECS), at 400-010-9 (ELINCS) and at 500-001-0 (NLP). This number is indicated in the column entitled ‘EC No’. CAS number
The Chemical Abstracts Service (CAS) number is also included to assist identification of the entry. It should be noted that the EINECS number includes both anhydrous and hydrated forms of a substance, and there are frequently different CAS numbers for anhydrous and hydrated forms. The CAS number included is for the anhydrous form only, and therefore the CAS number shown does not always describe the entry as accurately as the EINECS number. This number is indicated in the column entitled ‘CAS No’. International Chemical Identification
Wherever possible, hazardous substances are designated by their IUPAC names. Substances listed in EINECS, ELINCS or the list of ‘No-longer-polymers’ are designated using the names in these lists. Other names, such as usual or common names, are included in some cases. Whenever possible, plant protection products and biocides are designated by their ISO names.
Impurities, additives and minor components are normally not mentioned unless they contribute significantly to the classification of the substance.
Some substances are described with a specific percentage of purity. Substances containing a higher content of active material (e.g. organic peroxide) than this percentage are not included in the entry in Part 3 and may have other hazardous properties (e.g. explosive) and should be classified and labelled accordingly.
Where specific concentration limits are shown, these apply to the substance or substances shown in the entry. In particular, in the case of entries which are mixtures of substances or substances described with a specific percentage of purity, the limits apply to the substance as described in Part 3 and not the pure substance.
Without prejudice to Article 17(2), for substances appearing in Part 3, the name of the substance to be used on the label shall be one of the designations given there. For certain substances, additional information has been added in square brackets in order to help identify the substance. This additional information need not be included on the label.
Certain entries contain a reference to impurities; in these cases the name of the substance is followed by the text: ‘(containing ≥ xx % impurity)’. The reference in brackets is then to be considered as a part of the name, and must be included on the label. Entries for groups of substances
A number of group entries are included in Part 3. In these cases, the classification and labelling requirements will apply to all substances covered by the description.
In some cases, there are classification and labelling requirements for specific substances that would be covered by the group entry. In such cases a specific entry is included in Part 3 for the substance and the group entry will be annotated with the phrase ‘except those specified elsewhere in this Annex’.
In some cases, individual substances may be covered by more than one group entry. In these cases, the classification of the substance reflects the classification for each of the two group entries. In cases where different classifications for the same hazard are given, the most severe classification shall be applied.
Entries in Part 3 for salts (under any denomination) cover both anhydrous and hydrous forms, unless specified otherwise.
EC or CAS numbers are not usually included for entries which comprise more than four individual substances.