Sodium Phosphate, Dibasic
Title: Sodium Phosphate, Dibasic
CAS Registry Number: 7558-79-4
Additional Names: Dibasic sodium phosphate; disodium hydrogen phosphate; disodium orthophosphate; disodium phosphate; DSP; phosphate of soda; secondary sodium phosphate
Molecular Formula: HNa2O4P
Molecular Weight: 141.96
Percent Composition: H 0.71%, Na 32.39%, O 45.08%, P 21.82%
Line Formula: Na2HPO4
Literature References: Industrial production: Faith, Keyes & Clark's Industrial Chemicals (John Wiley, New York, 4th ed., 1975) pp 746-754. Toxicity of heptahydrate: H. F. Smyth et al., Am. Ind. Hyg. Assoc. J. 30, 470 (1969).
Properties: Anhydr, exsiccated sodium phosphate. Hygroscopic powder. On exposure to air will absorb from 2 to 7 mols H2O, depending on the humidity and temp. Sol in ~8 parts water, much more sol in hot water. Soly per 100 gal water increases from ~14 lbs at slightly >0° to over 900 lbs at 95°. Insol in alc. pH of 1% aq soln at 25°: 9.1. Keep well closed.
 
Derivative Type: Dihydrate
Additional Names: Sorensen's phosphate; Sorensen's sodium phosphate
 
Derivative Type: Heptahydrate
Properties: Crystals or granular powder. Stable in the air. d ~1.7. Sol in 4 parts water, more sol in boiling water; practically insol in alcohol. The aq soln is alkaline, pH ~9.5. LD50 orally in rats: 12.93 g/kg (Smyth).
Density: d ~1.7
Toxicity data: LD50 orally in rats: 12.93 g/kg (Smyth)
 
Derivative Type: Dodecahydrate
Properties: Translucent crystals or granules; readily loses 5 mols of water on exposure to air at ordinary temp. mp 34-35° (when it contains the full 12 mols of H2O). d ~1.5. Sol in 3 parts water; practically insol in alcohol. Aq soln is alkaline, pH ~9.5. Keep well closed and in a cool place. Incompat: Alkaloids, antipyrine, chloral hydrate, lead acetate, pyrogallol, resorcinol.
Melting point: mp 34-35°
Density: d ~1.5
 
CAUTION: Anhydr form may cause mild irritation to skin, mucous membranes; intern. causes purging.
Use: As sequestrant, emulsifier and buffer in foods. As mordant in dyeing; for weighting silk; in tanning; in manuf of enamels, ceramics, detergents, boiler compds; as fireproofing agent; in soldering and brazing instead of borax; as reagent and buffer in analytical chemistry.
Therap-Cat: Cathartic.
Therap-Cat-Vet: Laxative.
Keywords: Laxative/Cathartic.

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