Metallicity determination in gas-rich galaxies with semiempirical   methods
  A study of the precision of the semiempirical methods used in the determination of the chemical abundances in gas-rich galaxies is carried out. In order to do this the oxygen abundances of a total of 438 galaxies were determined using the electronic temperature, the $R_{23}$ and the P methods. The new calibration of the P method gives the smaller dispersion for the low and high metallicity regions, while the best numbers in the turnaround region are given by the $R_{23}$ method. We also found that the dispersion correlates with the metallicity. Finally, it can be said that all the semiempirical methods studied here are quite insensitive to metallicity with a value of $8.0\pm0.2$ dex for more than 50% of the total sample.   \keywords{ISM: abundances; (ISM): H {\sc ii} regions} 
A.M. Hidalgo-Gamez (ESFM-IPN, Mexico) and D. Ramirez-Fuentes (IA-UNAM,   Mexico)