The testing of oil pipe leakagecan be carried out cheaply bymean of 131I-iodobenzene labelled compound. Labelling of iodobenzene with 131I in Indonesia wouldsave cost because it is not necessary to import131 I-iodobenzene from abroad. 131I-iodobenzene labelledcompound can be synthesized through iodination reaction of benzen and diazotation of anilin.Diazotation of anilin withNaNO2 in concentrate HCl was done and resulted benzendiazonium salt isiodinazed with mixture of KI and NaI (+Na131I) by heating at 80o C for one hour. The formediodobenzenfrom the reaction is purified by vapor destilation. Identification of iodobenzene was carriedout by FTIR spectroscopy, refractive index and thin layer chromatography.The analysis of FTIR andrefractive index of iodobenzen from cold synthesis is the same with that of FTIR and refractive index ofstandard iodobenzen. Labelling result of131I-iodobenzene showed a yield of 32,2% calculated fromadded 131I radioactivity and reacted benzendiazonium salt.Key word : 131 I-iodobenzene, iodination.Batan
