FIELD: analytical chemistry. SUBSTANCE: test sample is mixed with streams of ammonia buffer and eriochrome black T, whereupon optical density of resultant solution is measured. Solution stream is then mixed with magnesium ethylenediaminetetraacetate stream and optical density of colored solution is measured. From optical density values, using known methods, calcium and magnesium contents in sample are calculated. Method allows simultaneous determination of the two ions in the same sample. EFFECT: increased reproducibility, selectivity, and productivity of analysis. 1 dwg, 1 tbl
