The Stretching Frequencies of Isotopic Arsenate and Permanganate Ions in Aqueous Solutions

The infrared absorption of crystalline powders and D 2 O solutions of normal and 84.5 atom % 18 O‐labelled sodium arsenate as well as normal and 83.3 atom % 18 O‐labelled sodium permanganate was measured in the 780–980 cm −1 region. The ν 1 and ν 3 fundamentals of the aqueous As 18 O 4 3− ion appear at 834(sh) and 866(s) cm −1 while the respective As 18 O 4 3− values are 808 and 822 cm −1 These as well as other data are shown to indicate that the water molecules which hydrate this ion are attached to its As atom. The ν 3 frequency of the aqueous Mn 18 O 4 − ion is observed at 917 cm −1 and that of hydrated Mn 18 O 4 − at 878 cm −1 .