Sodium acid metaphosphates

When sodium acid metaphosphate was first discovered, one form of [Na2H(P03)3]n salt was extremely easy to crystallize as a pure compound. After some initial work was completed, I decided that the remainder of this system should be explored. Three more new salts were discovered, but the initial supply of the first discovered salt had become exhausted. 

The salt, [Na2H(P03)3]n, had been so easy to prepare that there was no doubt that a new batch would be no problem to obtain as a pure salt. This did not prove to be the case. Salts on either side of these crystals were more easily crystallized than the initial salt, after seed crystals of the other two salts had been made. More salt was required to determine precisely its composition. It required almost two years of continuous repeated efforts to prepare the initial salt a second time in a pure condition. 

The salt could not be prepared according to the instructions in my own notebook. I finally devised a new route to the crystals. Even then, this compound was obtained in very small amounts, compared to the several hundred gram samples that were obtained before this system became contaminated by other crystals of the same system. It was a hard lesson in the power of seed crystals in condensed phosphate systems. 

Seeding is very important when growing condensed phosphates, and yet seeding is very poorly understood. Currently it is impossible to know, before a crystal is tried experimentally, whether or not it will induce crystallization in a melt. The first crystals of the sodium acid metaphosphate system were obtained while passing an electrical current through a melt of an amorphous salt. It was never known for certain if this was responsible for the crystallization, or was merely chance and crystallization would have occurred spontaneously without the electric 

The Phase Rule and Heterogeneous Equilibrium, Van Nostrand, New York (1951). G. W. Morey, Properties of Glass, American Chemical Society Monograph, Reinhold, New York (1954). 

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NaH2(P03)3l Sodium dihydrogen polyphosphate (sodium acid metaphosphate)... 

Two of the new salts discovered in the sodium acid metaphosphate were fibrous with asbestiform crystals and both are respectable candidates for fiber applications. If the salt, [Na2H(P03)3] , was ever to be practical, a better way of crystallization was surely required. The salt [Na3H(P03)4]n was very easily made and had properties that should have been quality fibers. It had a very slow rate of solution and was similar to Maddrell s salt in many of its properties. The phase diagram for this system is presented in Figure 5.9. The diagram was particularly difficult to obtain because these salts were inclined to become unstable at temperatures approaching their melting temperatures. 

Figure 5.9. The phase diagram for the sodium acid metaphosphate system area A contains Na2H2(P03>4 plus liquid area B contains Na2H(P03>3 plus liquid area C contains Na3H(P03>4 plus liquid area D contains [NaPOa] plus liquid.

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. 

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. 

Properties (1) White, crystalline powder. Slightly hygroscopic. Very soluble in water. Has acid reaction forms sodium acid pyrophosphate at 225-250C and sodium metaphosphate at 350 100C (2) large transparent crystals. Mp loses water at 100C, d 2.040. Very soluble in water insoluble in alcohol pH of 1% solution 4.4 1.5. Nonflammable. 

Sodium Phosphate Monosodium Phosphate (Msp, Sodium Phosphate, Monobasic) Disodium Phosphate (Dsp, Sodium Phosphate Dibasic) Trisodium Phosphate (TSP, Sodium phosphate, Tribasic) Sodium Acid Pyrophosphate (ASPP, SAPP, Disodium Pyrophosphate (TSPP) Sodium Metaphosphate (Insoluble Sodium Metaphosphate)... 

MSG-329. See Polyacrylamide MSM. See Dimethyl sulfone MSMA. See Sodium acid methanearsonate M Sodium Siiicate. See Sodium silicate MSP. See Sodium phosphate MSS-500/3H4] MSS-500/20N. See Silica MSTFA. See N-Methyl-N-trimethylsilyltrifluoroacetamide MSW-105. See Tetrapotassium pyrophosphate MSW-109. See Zinc phosphate MSW-600. See Sodium metaphosphate,... 

Citric acid Citric acid monohydrate Ethylenediamine Glycine Hydrochloric acid Magnesium carbonate Magnesium oxide Potassium carbonate Potassium citrate Potassium metaphosphate Potassium phosphate Potassium phosphate dibasic Sodium acetate anhydrous Sodium citrate Sodium hydroxide Sodium lactate Sodium phosphate Sodium phosphate dibasic anhydrous Sodium phosphate dibasic heptahydrate Sodium tri 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. 

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. 

G. Tammann found that when the mother liquid remaining after the neutralization of a soln. of metaphosphoric acid with sodium carbonate, has been evaporated at 50°, crystals of what G. Tammann calls sodium /9-monometaphdsphate are obtained. These are dried on porous tiles. The salt is readily transformed into the orthophosphate. G. Tammann obtained potassium /9-metaphosphate in a similar manner. The mol, formula is not known. 

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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