“…The published photometric procedures disagreed on the best wave length for measuring the absorbance of the yellow molybdosilicic acid. Recommended wave lengths in millimicrons were: 370 (11), 390 (9), 390 to 400 (10), 400 (2), 405 (4), 410 (7), 420 (17), and 425 (5). At the time of the initiation of this work only the paper of Armand and Berthaux (2) showed the spectrum.…”