Common impurities of (CAS NO. ) are water and peroxides [detected by the liberation of iodine from weakly acid (HCl) solns of 2% KI]. Peroxides can be removed by shaking with aqueous Na₂SO₃ or with acidified ferrous sulfate (0.6g FeSO₄ and 6mL conc H₂SO₄ in 110mL of water, using 5-10g of soln per L of ether), or aqueous NaBH₄ soln. The ether is then washed with water, dried with CaCl₂ and distd. Alternatively, refluxing with LiAlH₄ or CaH₂, or drying with CaSO₄, then passage through an activated alumina column, can be used to remove water and peroxides. Other dehydrating agents used with isopropyl ether include P₂O₅, sodium amalgam and sodium wire. (The ether is often stored in brown bottles, or in the dark, with sodium wire.) Bonner and Goishi treated isopropyl ether with dil sodium dichromate/sulfuric acid soln, followed by repeated shaking with a 1:1 mixture of 6M NaOH and saturated KMnO₄. The ether was washed several times with water, dilute aqueous HCl, and water, with a final washing with, and storage over, ferrous ammonium sulfate acidified with H₂SO₄. Blaustein and Gryder, after washing with alkaline KMnO₄, then water, treated the ether with ceric nitrate in nitric acid, and again washed with water. was added before drying with CaCl₂ and MgSO₄, and refluxing with sodium amalgam (108g Hg/100g Na) for 2h under nitrogen. The distillate (nitrogen atmosphere) was made 2x10^-5 M in hydroquinone to inhibit peroxide formation (which was negligible if the ether was stored in the dark). (pyrocatechol) and resorcinol are alternative inhibitors.