The Old IUPAC system labeled columns with Roman numerals followed by either the letter A or B. Columns were numbered such that columns one through seven were numbered IA through VIIA, columns 8 through 10 were labeled VIIIA, columns 11 through 17 were numbered IB through VIIB and column 18 was numbered VIII. Because of the confusion the old IUPAC and the CAS system created, the IUPAC adopted their new system.
Mostrar vella IUPAC: O sistema vello da IUPAC marcaba as colunas con números romanos seguidos polas letras A ou B. As colunas foron numeradas de maneira que as do un ao sete eran da IA á VIIA, as colunas da 8 á 10 eran a VIIIA, da 11 á 17 eran numeradas da IB á VIIB e a coluna 18 era numerada VIII. Por mor da confusión que criaron os sistemas vello da IUPAC e o do CAS, a IUPAC adoptou o seu novo sistema.