Sodium Polymetaphosphate Grahams Salt

Sodium trimetaphosphate can be prepared by (1) heating sodium dihydrogen orthophosphate for 5 hours at 530° or (2) tempering a glassy sodium metaphosphate at 520° fo 12 hours. If the product obtained by the first of these procedures is not entirely water-soluble, additional heating will be necessary to eliminate the insoluble polymer that forms at a lower temperature. 

The 6-hydrate, NasPsOg-fiHjO, is prepared in the following manner Fifty-one grams (0.166 mol) of anhydrous sodium trimetaphosphate is dissolved in 160 ml. of water at room temperature. Forty-five milliliters of a saturated solution of sodium chloride is added and the mixture agitated for 4 hours. The crystalline product, amounting to 23 g. (33 per cent of theory), is filtered and dried in air. 

The glass obtained by rapidly chilling a sodium metaphosphate melt is the highly polymerized polymetaphosphate. It can be prepared by heating any sodium phos- 

Anhydrous sodium trimetaphosphate is crystalline and water-soluble, but has no calcium-sequestering value. The trimetaphosphate is not precipitated by zinc, silver, or barium ions. Slow hydrolysis occurs in aqueous solution to give orthophosphate ions with intermediate formation of triphosphate ions. Conversion to triphosphate occurs very rapidly when the trimetaphophate is heated for a few minutes at 100° in the presence of an excess of sodium hydroude. No satisfactory quantitative method for its determination has been reported. It can, however, be identified by its refractive indexes, since the crystals are biaxial negative with a = 1.471, jS = 1.476, y = 1.480 ( .002). 

Crystals of the 6-hydrate, NajPj09-6H20, are triclinic rhombohedra, biaxial negative Avith a = 1.433, jS = 1.442, and y = 1.446 ( .002). These crystals are efflorescent at room temperature, lose water rapidly at 50°, and melt in their water of crystallization if heated rapidly to around 63°. 

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Sodium Polymetaphosphate. Graham s salt "sodium hexametaphosphate glassy sodium metaphosphate Hy-Phos. (NaPO. A mixture of polymeric metaphos-... 

Synonyms Graham s salt, Sodium hexametaphosphate, Sodium polymetaphosphate. Appearance White flaky crystals or granules small, broken, glass-like particles. 

Synonyms Glassy sodium Graham s salt Hexametaphosphate sodium salt Hexa-sodium metaphosphate HMP Metaphosphoric acid, hexasodium salt Phosphate, sodium hexameta- SHMP Sodium phosphate glass Sodium polymetaphosphate Classification Inorganic salt Ionic Nature Anionic Empirical O jPg 6Na Formula (NaPOjjg... 

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