Synthesis of selenium dioxide

Preparation of selenium dioxide

Selenium dioxide is prepared by the oxidation of selenium with nitric acid, followed by dehydration of the selenious acid.

Preparation of selenium dioxide

Preparation of selenium dioxide

70.5 ml (or 100 grams) of concentrated nitric acid are heated in a 1-liter beaker, and 50 grams of powdered selenium are cautiously added in small portions. The frothing should be allowed to subside after each addition before more selenium is introduced into the nitric acid. The dissolution of the selenium can be accelerated by mechanical stirring with a glass stirrer, moreover, this will break the foam produced. If not all selenium has been dissolved the additional amount of concentrated nitric acid is added until the selenium is completely dissolved. Then the solution is transferred to a large evaporating dish and heated at a temperature not exceeding 200° C. The selenious acid is completely dehydrates forming the dry residue, which is purified by treating crude selenium dioxide with sufficient water to dissolve it, and, after filtering from any insoluble residue, 10 ml of concentrated hydrochloric acid are added. A slow stream of sulfur dioxide is passed into the solution until heat is no longer evolved. This process can take up to 2-5 hours and the reaction is complete when the red precipitate of selenium settles to the bottom in a coherent mass, which upon standing for a few hours or, faster, on boiling for a short time, the red selenium passes into a pasty grey form, which eventually becomes brittle. The obtained selenium is filtered off, ground in a mortar, washed in order to remove hydrochloric acid, dried, and finally heated with the Bunsen burner over a free flame. Then the mass is cooled to room temperature, dissolved in the concentrated nitric acid and evaporated as described before. After removing all the nitric acid, the residue is dissolved in 70-80 ml of water and evaporated again yielding white selenium dioxide with 90% yield.

The crude selenium dioxide also could by purified by placing in a large porcelain crucible. Two nested funnels are inverted over the crucible, the larger funnel having a plug of glass wool in the neck. The crucible is heated for 20-25 minutes with a small flame until sublimation is complete. When the crucible has cooled, the resublimed selenium dioxide formed as in long needle-like crystals is removed and stored in a tightly stoppered bottle. The yield of selenium dioxide is about 63 g.

A text book of practical organic chemistry, by A. I. Vogel, 200-201, 1974


selenium dioxide



InChI Key


Canonical SMILES


MeSH Synonyms

Dioxide, Selenium, Monoxide, Selenium, Oxide, Selenium, Oxides, Selenium, selenium dioxide, Selenium Monoxide, selenium oxide, Selenium Oxides, selenium trioxide, Trioxide, Selenium

Depositor-Supplied Synonyms

SELENIUM DIOXIDE, Selenium oxide, Selenium(IV) oxide, Oxoselane oxide, Selenious anhydride, Selenium oxide (SeO2), Seleniumdioxide, 7446-08-4, Selenium dioxide dimer, Selenous acid anhydride, Selenium(IV) dioxide (1:2), Selenium oxide (Se2O4), RCRA waste number U204, Selenium(IV) dioxide, Selenium oxide (1:2), SELENIUM (IV) OXIDE, CCRIS 5820, HSDB 677, JPJALAQPGMAKDF-UHFFFAOYSA-N, EINECS 231-194-7, NSC 56753, 12397-00-1, Selenous anhydride, Oxoselane oxide #, (oxo-, SeO2, Selenium oxide, SeO2, ACMC-1BIBZ, DSSTox_CID_1264, AC1Q5B7Z, DSSTox_RID_76046, WLN: SE O2, DSSTox_GSID_21264, UNII-9N3UK29E57, (oxo-|E?-selanylidene)oxidane, (oxo-|E6-selanylidene)oxidane, 200107_ALDRICH, 204315_ALDRICH, 213365_ALDRICH, 325473_ALDRICH, AC1L2N58, AC1Q5B83, CHEMBL3183452, CTK2H7671, MolPort-001-783-720, NSC56753, EINECS 235-738-4, Tox21_202597, ANW-49393, NA2811, NSC-56753, STL264213, AKOS015855284, MCULE-7119785212, RTC-064135, Selenium oxide [NA2811] [Poison], NCGC00260145-01, 12640-89-0, BP-21360, 13814-59-0 (cadmium[1:1] salt), CAS-7446-08-4, DB-004088, LS-144814, TC-064135, 15702-34-8 (manganese(+2)[1:1] salt), A838139, 3B4-1538, I14-4773

Removed Synonyms

RCRA waste no. U204, CID24007

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