1994GB/T 223.21-1994 Methods for chemical analysis of iron steel and alloy.The 5-CL-PADAB spectrophotometric method for the determination of cobalt content
1982GB 223.21-1982 Chemical analysis of iron,steel and alloy--The determination of cobalt by the 5-Cl-PADAB photometric method
GB 223.21-1982 Chemical analysis of iron,steel and alloy--The determination of cobalt by the 5-Cl-PADAB photometric method was changed to GB/T 223.21-1994 Methods for chemical analysis of iron steel and alloy.The 5-CL-PADAB spectrophotometric method for the determination of cobalt content.