The light absorptions of complexes between EDTA and various metallic ions were measured by using Beckmann model DU spectrophotometer and it was found that a new double complex consisting of EDTA, Cr_2O_7^ and Co_ had strong absorbancy. Utilizing the nature of this complex spectrophotometric determinations of chromium and cobalt were investigated and 5~30γ/ml of chromium and 10~80γ/ml of cobalt could be determined under certain conditions. The composition of this complex was suggested to be (Co-EDTA)_7Cr_2O_7