GB/T 223.39-1994 Methods for chemical analysis iron,steel and alloy. The sulphochlorophenol S photometric method for the determination of niobium content (English Version)
2007GB/T 223.40-2007 Iron, steel and alloy Determination of niobium content by the sulphochlorophenol S spectrophotometric method
1994GB/T 223.39-1994 Methods for chemical analysis iron,steel and alloy. The sulphochlorophenol S photometric method for the determination of niobium content
1985GB 223.39-1985 Methods for chemical analysis of iron,steel and alloy--The sulphochlorophenol S photometric method for the determination of niobium content
GB/T 223.39-1994 Methods for chemical analysis iron,steel and alloy. The sulphochlorophenol S photometric method for the determination of niobium content was changed to GB/T 223.40-2007 Iron, steel and alloy Determination of niobium content by the sulphochlorophenol S spectrophotometric method.