It has been studied complex forming of copper (II) with 2,3,4-trihydroxyphenylazo-5¢-sulfonaphthaline(R₁) at presence (2-imino-4-oxotiazolidin-5-il) of an acetic acid (R₂) and 5(2¢-hydroxyphenyliden)tiazolidin-2,4-dion (R₃). Optimum conditions of complex formation are established; the constant of balance of reactions is calculated. It has been studied the selectivity of reaction and the constant of stability of complexes is calculated. Techniques of photometric definition of copper in alloys and in soils are developed