4137 / Mole (amount of substances): primaere Referenzlљsungen und Periodensystem at the PTB, Braunschweig: EUROPA, DEUTSCHLAND, BRAUNSCHWEIG (BRAUNSCHWEIG, GERMANY), 22.11.2007: Flasks with primary element reference solutions for dissemination of the SI base unit of amount of substance, the mole; Physikalisch-Technische Bundesanstalt PTB in Braunschweig, Germany. PTB-made elemental solutions act as transfer standards for calibration of industrial applications for chemical measurements. Blue: copper Cu, red: cobalt Co, green: nickel Ni, black: chromium Cr, clear: magnesium Mg and iron Fe. In back: periodic table.) - Marc Steinmetz / VISUM - Keywords: Germany, Physikalisch, Technische, Bundesanstalt, PTB, science, technology, metrology, base, unit, international, system, of, units, SI, metrical, measure, measurement, standard, lab, chemistry, amount, of, substance, mole, element, elements, reference, solutions, flask, periodic, table