Sodium selenite

Description

Sodium selenite (Na2SeO3) is a toxic inorganic salt that is highly soluble in water and insoluble in organic solvents. The crystal structure of the anhydrous salt has been variously reported as tetragonal or monoclinic.
In 1889, Irish chemists Sir Charles A. Cameron* and John Macallan produced Na2SeO3 and the previously unknown selenium oxychloride1 (SeOCl2) by heating selenium oxide (SeO2) with sodium chloride. This finding was reported in a pioneering series of articles on selenium chemistry.
In an improved 1929 synthesis, J. B. Krak at the Roessler and Hasslacher Chemical Co. (Perth Amboy, NJ) prepared Na2SeO3 by evaporating a solution of sodium hydroxide and selenious acid (H2SeO3) at 60–100 °C. Commercial Na2SeO3 is now made by heating an aqueous solution of SeO2 and NaOH to form its pentahydrate2, which is crystallized and then warmed to 40 °C to liberate the anhydrous salt.
Na2SeO3 and other selenite salts are used to “neutralize” green impurities during the manufacture of colorless glass. Iron-containing impurities in the natural silicas (e.g., sand) used to make glass absorb red and blue wavelengths of light, giving it a green appearance. Selenites have no color; but when they are dissolved in the glass mixture, they appear pinkish, counteracting the green hue and making the glass colorless.

Chemical properties

White to light beige crystals

Chemical properties

Sodium selenite is a white crystalline substance.

The Uses of Sodium selenite

Sodium selenite Na2O3Se is used in the production of red enamels and in the manufacture of clear red glass.

The Uses of Sodium selenite

Used in reducing carcinogenesis with potency greater than selenomethionene

The Uses of Sodium selenite

Removing green color from glass during its manufacture; alkaloidal reagent.

What are the applications of Application

Sodium selenite is used in reducing carcinogenesis

Definition

ChEBI: An inorganic sodium salt composed of sodium and selenite ions in a 2:1 ratio.

General Description

A white colored crystalline solid. Soluble in water and more dense than water. Contact may irritate skin, eyes and mucous membranes. Toxic by ingestion, inhalation and skin absorption.

Air & Water Reactions

Soluble in water.

Reactivity Profile

Sodium selenite is incompatible with strong acids.

Hazard

Toxic by ingestion.

Health Hazard

Toxic by ingestion. In humans, a concentration of 5 ppm in food or 0.5 ppm in milk or water has been estimated to be dangerous. Elemental selenium has low acute systemic toxicity, but dust or fumes can cause serious irritation of the respiratory tract.

Fire Hazard

May burn but will not ignite readily. When heated to decomposition, may emit toxic fumes of selenium and sodium oxide. Stable in air.

Flammability and Explosibility

Non flammable

Safety Profile

Poison by ingestion, intraperitoneal, intravenous, subcutaneous, intracervical, parenteral, and intramuscular routes. Experimental teratogenic and reproductive effects. Questionable carcinogen. Human mutation data reported. When heated to decomposition it emits toxic fumes of Se and Na2O. See also SELENIUM COMPOUNDS.

Potential Exposure

Sodium selenite is used in glass manufacturing and as an alkaloidal reagent; for removing green color from glass during its manufacture; alkaloidal reagent; reagent in bacteriology; testing germination of seeds; decorating porcelain; as a livestock feed additive.

Shipping

UN2630 Selenates or Selenites, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Purification Methods

Crystallise sodium selenite from a saturated aqueous solution where its solubility is 68% at 20o to give the pentahydrate salt. This yields the anhydrous salt on heating at 40o. [Fehér in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 431 1963].

Incompatibilities

The aqueous solution is a medium strong base. Reacts with water, strong acids; hot surfaces; causing decomposition and a toxic hazard.

Waste Disposal

Liquid or solid: make a strongly acidic solution using hydrochloric acid. Slowly add sodium sulfite to the cold solution. Stir mixture producing sulfur dioxide. Heat, forming dark-gray selenium and black tellurium. Let stand overnight. Filter and dry. Ship to supplier.