Tetrasodium pyrophosphate

Disodium dihydrogen pyrophosphate dissolves slowly in cold water, a 1 per cent solution having a pH of 4.1 to 4.3. One hydrate, Na2H2P207 6Ha0, can be crystallized from aqueous solutions at slightly below room temperature. The hydrated crystals are biaxial negative with a = 1.456, jS = 1.464, and 7 = 1.465( .002). When heated they lose their water of crystallization around 36°. In aqueous solution the disodium pyrophosphate hydrolyzes to orthophosphate, the rate of hydrolysis depending on the temperature. At 70° a 1 per cent solution is hydrolyzed approximately 10 per cent in 6 hours at 100° the hydrolysis is complete in less than 6 hours.  

When anhydrous disodium dihydrogen p3Tophosphate is prepared by the acetic acid method, the product is sufficiently crystalline for optical measurements. The crystals are orthorhombic pyramids, biaxial negative with a = 1.501 . 002, 8 = 1.514 . 005, and 7 = 1-522 . 002. Ingerson and Morey give a = 1.510 and 7 = 1.517 for very fine needle crystals. 

Tetrasodium pyrophosphate is quite soluble in cold water a 1 per cent solution has a pH of 10.2. It hydrolyzes to orthophosphate in aqueous solution but the rate of 

Conditioners are surfactants that neutralize the electrical charge on the surface of the hair, and smooth down protein scales on the hair shafts. These effects make the hair easier to style and less prone to static electricity. 

Conditioners can be made from oily surfactants or fatty surfactants, or a mixture of both. The more solid fatty conditioners can glue together split ends and damaged hair. The more liquid oily conditioners smooth the hair and then rinse out more effectively. 

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Crystalline CaHPO 2H20 loses both water molecules in a single step at moderately elevated temperature or upon storage to yield the anhydrous salt. The presence of free moisture accelerates this dehydration, which results in anhydrous dicalcium phosphate, often as a hard mass. Addition of a few percent of tetrasodium pyrophosphate or trimagnesium phosphate, Mg2(P0 2> stabilizes the dihydrate. The mechanism, however, is not well understood. Nonetheless, these materials are used widely to stabilize CaHPO 2H20, particulady for toothpaste appHcations. 

Sodium Pyrophosphates. Known pyrophosphate compounds in the Na20—H2O—P20 system are given in Table 10. Commercially important sodium pyrophosphates include tetrasodium pyrophosphate (TSPP), Na4P20y, and disodium pyrophosphate, Na2H2P20y, commonly referred to as sodium acid pyrophosphate (SAPP). These are prepared industrially by thermal dehydration of disodium and monosodium orthophosphate, respectively. Tetrasodium pyrophosphate exists in five crystalline modifications, only one of which is stable at room temperature. 

TSPP is readily crystallised from water as the decahydrate between —0.4° and 79°C, and as the anhydrous salt above 79°C. The solubiUty of tetrasodium pyrophosphate is illustrated in Figure 8. The pH of a 1% solution is 10.2. TSPP is quite stable in alkaline medium but hydrolyses rapidly to orthophosphate under acid conditions. 

Fig. 8. Solubihties of sodium acid pyrophosphate and tetrasodium pyrophosphate.

Sodium tripolyphosphate is produced by calcination of an intimate mixture of orthophosphate salts containing the correct overall Na/P mole ratio of 1.67. The proportions of the two anhydrous STP phases are controlled by the calcination conditions. Commercial STP typically contain a few percent of tetrasodium pyrophosphate and some trimetaphosphate. A small amount of unconverted orthophosphates and long-chain polyphosphates also may be present. 

Tetrasodium pyrophosphate [7722-88-5] Na4P20y, is another important primary builder and detergent. In sequestration, it is not quite as effective as sodium tripolyphosphate and its usage in heavy-duty laundry powders has declined in recent years. Functionally, tetrasodium pyrophosphate is both a builder for surfactants (ie, water softener) and alkaH. 

Condensed Phosphates. The term condensed phosphate refers to any dehydrated, condensed orthophosphate for which the M20 P20 ratio is less than 3 1 (17). (1) is disodium orthophosphate [7558-79-4] and (2) tetrasodium pyrophosphate [7722-88-5]. 

Scouring may be conducted on jigs, boil-off machines, or kettles, depending on fabric weight, constmction, and crease tendency ia the rope form. A combination of a synthetic detergent and soda ash is usually used and scouring is conducted at 85—100°C. Certain nylon blends may require less stringent conditions and the use of less alkaline builders, such as tetrasodium pyrophosphate. 

Cellulose Diacetate. When preparing cellulose diacetate for dyeing, strong alkahes must be avoided in the scouring of acetate because the surface of the cellulose acetate would be saponified by such treatment. Many fabrics tend to crease and therefore requke open-width handling. Scouring is frequendy carried out on a jig or beam using 1.0 g/L of surfactant and 0.5—1.0 g/L tetrasodium pyrophosphate for 30 min at 70—80°C. 

Elastomeric Fibers. Elastomeric fibers are polyurethanes combiaed with other nonelastic fibers to produce fabrics with controlled elasticity (see Fibers, elastomeric). Processing chemicals must be carefully selected to protect all fibers present ia the blend. Prior to scouriag, the fabrics are normally steamed to relax uneven tensions placed on the fibers duriag weaving. Scouriag, which is used to remove lubricants and siting, is normally conducted with aqueous solutions of synthetic detergents and tetrasodium pyrophosphate, with aqueous emulsions of perchloroethylene or with mineral spidts and sodium pyrophosphate. 

A novel method for preparing amino heterocycles is illustrated by the preparation of 2-amino-5-methylthiophene (159). In this approach vinyl azides act as NH2 equivalents in reaction with aromatic or heteroaromatic lithium derivatives (82TL699). A further variant for the preparation of amino heterocycles is by azide reduction the latter compounds are obtained by reaction of lithio derivatives with p- toluenesulfonyl azide and decomposition of the resulting lithium salt with tetrasodium pyrophosphate (Scheme 66) (82JOC3177). 

Tetrasodium EDTA, 127 Tetrasodium pyrophosphate, 127 TETRA Technologies Inc., 250 Teti-yl, 127... 

Compounds with similar functions are sodium carbonate, sodium EDTA, phosphoric acid, pentasodium pentetate, tetrasodium etidronate, and tetrasodium pyrophosphate. 

Tetrasodium pyrophosphate is used as a pH buffer (a substance that maintains a particular acidity level), and as a dough conditioner in soy-based meat alternatives. It promotes binding of proteins to water, binding the soy particles together, and is used for the same purpose in chicken nuggets and imitation crab and lobster products. 

The sequestering agent tetrasodium pyrophosphate (TSPP) removes calcium and magnesium from the saliva, so they can t deposit on teeth as insoluble deposits called tartar (calcified plaque). In this respect it acts as a water-softening agent. However, it won t remove tartar that already exists. 

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