Sodium metaphosphate

The monofluorophosphates can be prepared by neutralization of monofluorophosphoric acid (1). Sodium monofluorophosphate [7631 -97-2] is prepared commercially (57) by fusion of sodium fluoride and sodium metaphosphate, and the potassium monofluorophosphate [14104-28-0] can be prepared similarly. Insoluble monofluorophosphates can be readily prepared from reaction of nitrate or chloride solutions with sodium monofluorophosphate. Some salts are prepared by metathetical reactions between silver monofluorophosphate [66904-72-1] and metal chlorides. 

Phosphate Esters. The phosphorylation of sucrose using sodium metaphosphate has been reported (78). Lyoptulization of a sodium metaphosphate solution of sucrose at pH 5 for 20 hours followed by storage at 80°C for five days produced a mixture of sucrose monophosphates. These products were isolated by preparative hplc, with a calculated yield of 27% based on all organic phosphate as sucrose monoesters. Small proportions of glucose and fmctose were also formed. 

An abrasive is usually chemically inert, neither interacting with other dentifrice ingredients nor dissolving in the paste or the mouth. Substances used as dentifrice abrasives include amorphous hydrated silica, dicalcium phosphate dihydrate [7789-77-7] anhydrous dicalcium phosphate [7757-93-9] insoluble sodium metaphosphate [10361-03-2], calcium pyrophosphate [35405-51-7], a-alumina trihydrate, and calcium carbonate [471-34-1]. These materials are usually synthesized to specifications for purity, particle size, and other characteristics naturally occurring minerals are used infrequently. Sodium bicarbonate [144-55-8] and sodium chloride [7647-14-5] have also been employed as dentifrice abrasives. 

Chemical Designations - Synonyms Sodium phosphate is generic term and includes the following (1) monosodium phosphate (MSP sodium phospWe, monobasic), (2) disodium phosphate (DSP sodium phosphate dibasic), (3) trisodium phosphate (TSP sodium phosphate, tribasic), (4) sodium acid pyrophosphate (ASPP SAPP disodium pyrophosphate (TSPP), (6) sodium metaphosphate (insoluble sodium metaphosphate), (7) sodium trimetaphosphate, and (9) sodium tripolyphosphate (STPP TPP) Chemical Formula (1) NaHjPO (2) Na HPO (3) NajPO (4) Na H P O, (5) Na P O, (6) (NaPOj) (7) (NaP03)3 (8) (NaP03) NaO (9) Na,P30,o. 

Sodium fluoride also attacks silica, as do sodium metaphosphate and sodium polyphosphate, and to a lesser extent sodium carbonate and sodium cyanide. Attack is particularly vigorous for fused alkalis, alkali halides and phosphates. 

Also introduced was sodium metaphosphate [Hagan phosphate or Calgon , represented at the time by the formula (NaP03)6, although it tends to have a different formula today]. 

Alternatively, sodium metaphosphate (an orthophosphate that has been molecularly dehydrated by the removal of a molecule of water) may be employed because this must regain the lost water molecule before reacting with calcium as the orthophosphate. This delay may provide the time necessary to ensure that the precipitation reaction takes place solely within the confines of the bulk BW. 

The earliest formulations, as reported by Rollins (1879), Gaylord (1889), Ames (1893), Hinkins Acree (1901) and Fleck (1902), were variously based on syrupy orthophosphoric acid or unstable mixtures of meta-phosphoric acid and sodium metaphosphate in solution. Some used solid pyrophosphoric acid. Many were grossly inferior cements which were hydrolytically unstable. 

A second neutralization is carried out with soda ash to a pH level of about 4. Special heating, agitation, and retention are next employed to adequately condition the slurry so that filtration separation of the contaminants can be accomplished. The remaining solution is sufficiently pure for the production of monosodium phosphate, which can be further converted into other compounds such as sodium metaphosphate, disodium phosphate, and trisodium phosphate. A typical process flow diagram is shown in Figure 6. Wastewater effluents from these processes originate from leaks and spills, hltration backwashes, and gas scrubber wastewaters. 

Anhydrous salt white crystalline powder slightly hygroscopic forms sodium acid pyrophosphate, Na2H2P20 on heating above 225°C and sodium metaphosphate (NaPOsln at about 350 to 400°C very soluble in water, aqueous solution acidic. 

Most of the world production of phosphates goes into fertilizer, but some is used as detergent builders (Section 7.7). In toothpastes, calcium pyrophosphate has proved effective as a mild abrasive in eliminating tartar, while Na2[FP03], made by reaction of NaF with cyclic sodium metaphosphates (NaP03), is widely used as a fluoridating agent to suppress dental caries (Section 12.3). A minor amount of rock phosphate is used to make elemental phosphorus by reduction with coke in the presence of silica in the electric furnace (see Section 17.7) ... 

Metaphosphoric Acid. Reactions jor Determining Metaphosphoric Acid and Its Salts. 1. Pour about 1 ml of an aqueous protein solution into a test tube and add to it approximately the same amount of a sodium metaphosphate solution acidified with acetic acid. What do you observe See whether the protein solution is affected in the same way by sodium metaphosphate and acetic acid solutions taken separately. 

Pour a few drops of silver nitrate into a sodium metaphosphate solution. Note the colour of the precipitate. See how it reacts with dilute nitric acid. Write the equations of the reactions. In what medium can silver metaphosphate be precipitated ... 

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