A chloroform solution of N-benzoyl-N-phenylhydroxylamine(BPHA) may be used for extracting niobium from sulphuric or tartaric acid solution^[1],but the yellow colour of niobium-BPHA complex found in the organic layer is too pale to be applied for the colorimetric determination of micro amounts of niobium.It is found in our laboratory that through the addition of ammonium thiocyanate the colour intensity of the niobium complex increases greatly.As in the case of titanium^[2],the increase in colour intensity is due to the formation of a new niobium-BPHA-thiocyanate complex,the molecular extinction of which is found to be 46,500,30,700,and 18,000 at 360,380,and 420 mμ respectively.Based upon this highly sensitive reaction,a method of extraction and colorimetric determination of microgram amounts of niobium is suggested.