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of the violet solution, place into a cuvette and analyze by UV-Vis. This step must be done quickly, as V(II) is air-sensitive. [V(H2O)6] 3+ (green) In a 25 mL beaker with a stir bar, place 10 mL of the [VO(H2O)5] 2+ stock solution using a syringe. Using a syringe add 10 mL of the [V(H2O)6] 2+ solution and mix well. The solution will turn brown first then change color into a bluish green solution. Transfer into a cuvette and analyze by UV-Vis. If the band from [VO(H2O)5] 2+ is still present, add 0.25 mL of [V(H2O)6] 2+ .Repeat the procedure, possibly with smaller volume added, until no [VO(H2O)5] 2+ is detectable. Record the total volume of [V(H2O)6] 2+ solution you used. For comparison, take some of the remaining [V(H2O)6] 2+, place it in a beaker and stir in air. The purple V(II) is air-sensitive and will slowly oxidize to the green V(III). Data Table 1. Amount of Reagents Chemical Mass (mg)/volume (ml) Moles (mmol) NH 4 VO 3 10ml ---- VOSO 4 xH 2 O 0.3420 2.10 [V(H 2 O) 6 ] 2+ 10.25ml Table 2. Absorbance Maximum of Vanadium Species Species d n Color λ max (nm) VO 2 + d 0 Yellow N/A VO 2+ d 1 Blue 767 V 3+ d 2 Green 400, 604 V 2+ d 3 Purple 375, 560 Table 3. Racah Parameters for V 3+ and V 2+ Species B’ (cm -1 ) V 3+ 773 V 2+ 724