On the metallicities of UM 133, UM 283 and UM 382

The study of group properties of the extremely metal-deficient gas-rich local dwarfs is very promising for the understanding the galaxy formation process at high redshifts. About 20 such objects have been picked up from the literature in the recent review by Kunth & Ostlin ([CITE]). However part of these galaxies got low metallicity as a result of earlier observations, and can have rather large uncertainties in their cited element abundances. Before to perform the detailed studies of such galaxies as of some extreme group, it is useful to revise their metallicities. We present the results of the SAO 6 m telescope spectrophotometry of two Blue Compact Galaxies (BCG) reported from earlier studies as very metal-poor objects. Well measured [O iii] line λ 4363 A allows to deduce the temperature in Hii regions and get reliable abundances of chemical elements. For UM 133 we derive $12+\log({\rm O/H}) = 7.63\pm 0.02$, coincident with the published value. UM 382, according to our data, is significantly more metal-rich: its $12+\log({\rm O/H}) = 7.82\pm 0.03$ in comparison to the published value 7.45. The third galaxy, UM 283 seems have got its very low $12+\log({\rm O/H}) = 7.59$ due to a misprint. We used its published emission line intensities and derived instead the value of 7.95. Thus the latter two galaxies should NOT be considered as the extremely metal-poor BCGs.