SODIUM PYROPHOSPHATE

PRODUCT IDENTIFICATION
CAS NO. 7722-88-5 (Anhydrous)
13472-36-1 (Decahydrate)

SODIUM PYROPHOSPHATE
EINECS NO.  
FORMULA Na4P2O7
MOL WT. 265.90

H.S. CODE

 2835.39
SMILES

 

TOXICITY

 Oral rat LD50: 4000 mg/kg

SYNONYMS
Diphosphoric acid, tetrasodium salt;
Phosphotex; Pyrophosphoric acid, tetrasodium salt; Sodium Diphosphate; Sodium pyrophosphate (4:1); Tetrasodium diphosphate; Tetrasodium Pyrophosphate; TSPP;

CLASSIFICATION

 

PHYSICAL AND CHEMICAL PROPERTIES

PHYSICAL STATE

hygroscopic white crystals
MELTING POINT  
BOILING POINT  
SPECIFIC GRAVITY  
SOLUBILITY IN WATER

slowly hydrolysis to sodium orthophosphate. (insoluble in alcohol and ammine)
pH

10.0 - 10.5 (1% sol.)
VAPOR DENSITY  

AUTOIGNITION

 

NFPA RATINGS

 Health: 1; Flammability: 0; Reactivity: 0

REFRACTIVE INDEX

 
FLASH POINT  
STABILITY Stable under ordinary conditions

APPLICATIONS

Water softener; metal cleaner; soap and detergent builder; sequestering agent; in electrodeposition of metals; enamelling improvement; tin plating; china-clay purification; dyeing; oil-drilling muds; synthetic rubber production; cleaning agents and detergents - high solubility, hardness stabilization, soil dispersion; toothpaste - prevention of tarter
SALES SPECIFICATION

APPEARANCE

White Powder
ASSAY

95.0 % min

pH

 10.0 - 10.7 (1% sol.)

CHLORIDE(Cl)
0.01 % max

IRON(Fe)
0.01 % max
TRANSPORTATION
PACKING 25kgs in bag
HAZARD CLASS  
UN NO.  
DESCRIPTION OF 'PYRO-'
'pyro' is the chemical prefix for oxo acid formed through the loss of one water molecule from two molecules of an ortho acid (dehydration of two molecules by heating).  Pyrosulphuric acid is an example ( 2H2SO4 - H2O = H2S2O7). Otho acid is the compound fully hydrated acid or of its salts. Orthophosphoric acid is an example (H3PO4 = P2O5.3H2O), in contrast to the less hydrated form, metaphosphoric acid (HPO3 = P2O5.H2O). Pyrophosphoric acid is the anhydride of phosphoric acid obtained from dehydration of phosphoric acid.
GENERAL DESCRIPTION OF PHOSPHORIC ACID
Phosphoric Acid (also called Orthophosphoric Acid) is three chemicals compound made up of phosphorus, oxygen, and hydrogen. Otho acid is the compound fully hydrated acid or of its salts. Orthophosphoric acid is an example (H3PO4 = P2O5.3H2O), in contrast to the less hydrated form, metaphosphoric acid (HPO3 = P2O5.H2O). Phosphoric Acid is prepared commercially by heating calcium phosphate rock with sulfuric acid; purer grades may be prepared by treating red phosphorus with nitric acid. Pure phosphoric acid is a crystalline solid melting point 42 C; in less concentrated form it is a colourless syrupy liquid. It is a tribasic acid (having three replaceable hydrogen atoms) and forms orthophosphate salts with either one, two, or all three of the hydrogens replaced by some other positive ion. Phosphate is any of the salts or esters of phosphoric acid. One of the important phosphates is calcium phosphate, Ca3(PO4)2. The most important phosphorus fertilizer is monobasic calcium phosphate, called superphosphate[Ca(H2PO4)2], derived by treating rock phosphate with sulfuric acid (or phosphoric acid).  Superphosphate is soluble in water and acts as a carrier of phosphorus needed by plants. Dibasic calcium phosphate (CaHPO4) is used in pharmaceuticals, animal feeds, and toothpastes. Tribasic calcium phosphate, [Ca3(PO4)2] is used as a fertilizer as a plastics stabilizer. Other important inorganic phosphates include ammonium phosphate [(NH4)2HPO4] used as a fertilizer and fire retardant; trisodium phosphate used in detergents and for softening water; mono and disodium phosphate used for dispersion, sequestration, scale inhibition and preparing baking powders. The salt forms of phosphate polymers is used as a sequestering agent. As phosphate polymers themselves are hydrated in water at high temperature or high pH, and thereby revert to a more simple and stable phosphate form, which can no longer sequester metal ions. Phosphoric acid and phosphates are used to make phosphates for fertilizers, electro chemical polishing and shaping, electroplating, metal cleaning and pickling in metal treatment. They are also used in the manufacture of industrial cleaning and derusting solutions, for production of other inorganic and organic phosphoric chemicals, for foundry resins, for production of paints, enamels and refractories, for textile processing, for water treatment and for antifreeze production.

DESCRIPTION OF PHOSPHORUS
Phosphoric acid is a phosphorus-containing inorganic acid made up of phosphorus, oxygen, and hydrogen. In a broardened term, it includes the monomeric (orthophosphoric acid), dimeric (pyrophosphoric acid), and polymeric (metaphosphoric acid) forms of the acid.  Phosphoric acid commonly indicates the monomeric form orthophosphoric acid. On heating to about 225 C, it dehydrates to form pyrophosphoric acid and to metaphosphoric acid (2HPO3 = P2O5.H2O) at higher temperatures. Pyrophosphates are salts of pyrophosphoric acid and metaphosphates are salts of metaphosphoric acid. Two molecules of orthophosphoric acid are formed when three molecules of water are added to one molecule of phosphorus pentoxide (2H3PO4 = P2O5.3H2O). The pyrophosphates are formed by the loss of 1 molecule of water from 2 moles of an orthophosphate. Pure orthophosphoric acid is a crystalline solid; melting point 42 C; soluble in alcohol, and very soluble in water. Phosphoric Acid violently polymerizes under the influence of azo compounds, epoxides and other polymerizable compounds. It forms toxic fumes of phosphorous oxides when combusted. It is a medium strong acid and attacks metals to release flammable hydrogen gas. Decomposition may occur on contacting with alcohols, aldehydes, cyanides, ketones, phenols, esters, sulfides, halogenated organics compounds.

Phosphoric acid is essential in the body organism as the constituent of bones and teeth as well as in many metabolic process of carbohydrate, fat and protein. Phosphoric acid is abundant in natural foods as the form of free phosphoric acid itself or as the mineral salts (potassium, sodium or calcium). Phosphoric acid is used to acidify foods and beverages. But the continuous and excessive absorption of beverages particularly Coca Cola and Pepsi Cola which contain large amount of phosphoric acid should be limited. Phosphate excretion takes place in the form of calcium phosphate. The excessive amounts of phosphoric acid in the body may cause calcium deficiency which causes poor teeth and weak bone density (osteoporosis). Phosphoric acid is used in pharmaceutical preparations as a solvent and as a gastric acidifier orally.  Phosphoric acid is important raw material in industrial field. It is a tribasic acid (having three replaceable hydrogen atoms) which can forms phosphates with either one, two, or all three of the hydrogen by replacing with some other positive ion. The structure of the phosphate anion consists of phosphorus at the center of a tetrahedron defined by a solid bond between one oxygen atom and phosphorus and single bonds for the other oxygen atoms. In this very formal depiction, negative charge is localized on the O atoms of the single P-O bonds.  It is used in making fertilizers, electrolytes, electroplating and derusting solutions. It is used in the manufacture of industrial cleaning products, other inorganic and organic phosphoric chemicals, foundry resins, paints, enamels and refractory, antifreeze productions, and textile process materials. It is used in water treatment. Food grade phosphoric acid is used; as a acidulation in soft drink (particularly cola); ph control in imitation jellies; nutrient in production of yeast; bacteria growth control in selected processed foods; flocculating agent for clarification of sugar juices after liming process.

  • Phosphorous acid:  a diprotic acid which contains one hydrogen bonded directly to the central phosphorus atom and two hydrogens bonded to oxygen
  • Phosphite:any salt, ester or anion of phosphorous acid
  • Phosphate: any salt, ester or anion of phosphoric acid
  • Phosphide: any binary compound of phosphorus with another element or radical
  • Phosphine:  binary compound of phosphorus with hydrogen or organic compounds derived from this

One of the important phosphates is calcium phosphate, Ca3(PO4)2. The most important phosphorus fertilizer is monobasic calcium phosphate, called superphosphate[Ca(H2PO4)2], derived by treating rock phosphate with sulfuric acid (or phosphoric acid).  Superphosphate is soluble in water and acts as a carrier of phosphorus needed by plants. Dibasic calcium phosphate (CaHPO4) is used in pharmaceuticals, animal feeds, and toothpastes. Tribasic calcium phosphate, [Ca3(PO4)2] is used as a fertilizer and as a plastics stabilizer. Other important inorganic phosphates include ammonium phosphate [(NH4)2HPO4] used as a fertilizer and fire retardant; trisodium phosphate used in detergents and for softening water; mono and disodium phosphate used for dispersion, sequestration, scale inhibition and preparing baking powders. The salt forms of phosphate polymers is used as a sequestering agent. As phosphate polymers themselves are hydrated in water at high temperature or high pH, and thereby revert to a more simple and stable phosphate form, which can no longer sequester metal ions. Industrial phosphates are used in many applications including dispersion, sequestration and scale inhibition. Detergent application is important also, with products such as sodium tripolyphosphate being key ingredients in detergents. Phosphates are used in a wide range of  food products to perform several  functions like retention of natural fluids in the muscle that would otherwise be lost in the aging, cooking, or freeze-thaw processes. Polyphosphates also act in solubilization of myofibrillar proteins that aid in the binding of meat particles. Their presence results in stabilised texture, flavour, and colour.

Mono and dibasic phosphate esters produced by the reaction of either alcohols, alcohol ethoxylates or phenyl ethoxylates with polyphosphoric acid or phosphorous pentoxide are anionic surfactants which have the main feature of the stability in alkaline conditions over other surfactants. They have a wide range of properties including outstanding wetting, emulsification, lubrication, coupling activity and detergency. They exhibit the properties of anti-wear and corrosion inhibition either as free esters or in the forms of metal and amine salts. They are used in:
  • Heavy duty alkaline cleaning products
  • Laundry Detergents
  • Emulsion polymerisation
  • Textile auxiliaries
  • Acid cleaners
  • Metal working fluids
  • Emulsifiers
  • Wetters
  • Dispersants
  • Water based lubricants
  • Intermediate for the synthesis of other anionic surfactants

Phosphoric acid alkyl esters are also used as alkylation agent for nitrogen heterocyclic compounds and as catalysts to produce phenolic and urea resins. They are used flame retarding plasticizers for cellulose esters, lacquers, plastic and vinyl resins as well as as dispersing agents in plastisols. They are used as solvents in liquid-liquid extractants or separation agent of metals. They are is used as heat exchange media and as pigment grinding assistants and antifoam agents.