Sneddon, J.; Hunter, J. K.; Ottaway, J. M.; Fell, S. G. Analyst (London) 1981, 106, 288. Harnly, J. M.; Mlller-Ihll, N. J.; O'Haver, T. C. J. Aotom. Chem., in press. " Y Iare measured at only three wavelengths, the dynamic range will fall short of that which can be achieved using a bi-Gaussian wave. However, the construction of sectored wheels with more than fclur quadrants would eliminate this limitation.The equllibrlum constants for 9-, 11-, and 12-molybdophosphates were determined spectrophotometrically in strong acid solutions wlth the continuous variation method and with computer slmulatlons. For 12-moiybdophosphate, log K,, =:EXPERIMENTAL SECTION Reagents. A 0.5 M stock solution of Mo(V1) was prepared from reagent grade Na2Mo04-2Hz0 (Baker Chemical Co.). Stock solutions of HNO,, HC104, and H2S04 were prepared from the concentrated acid reagents and standardized with NaOH previously standardized with KHP. The stock phosphate solution was prepared from reagent-grade KH2P04, and the 5 M NaC10, stock solution used to control ionic strength was prepared from the reagent grade chemical (G. F. Smith Chemical Co.). This Mo(OH)S(HzO)", Mo20(0H)&O)+, M O~O ( O H )~( H~O )~~' ,