Three graded series of “Matthey” copper standards are in course of preparation, intended to cover the ranges 0.05% to 0.0001% of Al, Sb, Bi, Cr, Ga, Pb, Ag, Sn (Series A), Co, Fe, Mn, Ni, Si (Series B), and 0.05% to 0.001% of As, Be, P, Se, Te, Zn (Series C). Chemical analyses have been made of the 0.05% standards and the compositions of the dilutions of these alloys with pure copper are now being checked spectrographically, with particular reference to the standards containing the smallest amounts of added elements, using a globulo arc method. Plate calibration is effected by means of an iron arc spectrum and a correction for spectrum background is made for each line measured. By extrapolating the linear portion of the log ( I element/ I copper) versus log % element calibration curve, the residual impurities in the pure copper can be estimated. Satisfactory checks have been obtained in the case of bismuth, silver, tin, cobalt, and manganese and the investigation of the remaining elements is in progress.