Sodium selenite pentahydrate

Edit Preparation Sodium selenite is produced by neutralizing selenite with sodium hydroxide:
An accurately measured solution of carbonate-free sodium hydroxide is mixed with a concentrated solution of selenite in the amount required for the above chemical reaction. The solution was subjected to vacuum evaporation over anhydrous calcium chloride at room temperature. Since this salt tends to form a supersaturated solution, the walls of the apparatus may be rubbed with a glass rod at the end of the evaporation to promote the precipitation of crystals. In order to obtain larger crystals, the precipitated microcrystals can be added to the saturated solution as a seed and evaporation is continued. Na2SeO3-5H2O can be produced by draining the crystals with a glass sand-core funnel and placing them in a desiccator without desiccant to remove the water adhering to the surface of the crystals.
Main uses
Edit Used for the prevention and control of Keshan disease has achieved remarkable results, and is also effective in preventing selenium deficiency in livestock. Used as a reagent for testing alkaloids and seed germination, and also used as an agent for red glass and glaze. It has been used in the prevention and control of Creutzfeldt-Jakob disease, and is also effective in the prevention of selenium deficiency in livestock.
Safety Information
Edit Risk terminology
R23:Toxic by inhalation.
R28:Very toxic if swallowed.
R31:Contact with acids liberates toxic gas.
R43:May cause sensitization by skin contact.
R51/53:Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.