FIELD: analytical methods. SUBSTANCE: for spectral determination of boron in carbon-graphite powders and fibers as well as in mineralized organic-origin samples, carbon-graphite material contains, as active additive, 1 to 10% of urea. EFFECT: reduced systematic and accidental constituents of error caused by difference in forms of boron compounds contained in samples and standards. 3 dwg, 3 tbl
