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Home> Encyclopedia >Phosphate>Pharmaceutical Intermediates>Other Inorganic Salts
Potassium pyrophosphate structure
Potassium pyrophosphate structure

Potassium pyrophosphate

Iupac Name:tetrapotassium;phosphonato phosphate
CAS No.: 7320-34-5
Molecular Weight:330.334
Modify Date.: 2022-12-06 15:34
1. Names and Identifiers
1.1 Name
Potassium pyrophosphate
1.2 Synonyms

Potassium Diphosphate 〔Potassium Pyrophosphate〕 Potassium pyrophosphate tetrabasic PYROPHOSPHATE TETRAPOTASSIUM*PRACTICAL GRADE Tetra-PotassiumPyrophosphateExtraPure TetraPotassiumPyrophosphateFoodGrade TetraPotassiumPyrophosphateTechGrade TkppAnhydrous-TetrapotassiumPyrophosphate

1.3 CAS No.
1.5 Molecular Formula
K4O7P2 (isomer)
1.6 Inchi
1.7 InChIkey
1.8 Canonical Smiles
1.9 Isomers Smiles
2. Properties
2.1 Density
2.1 Melting point
1300 °C (lit.)
2.1 PH
Between 10,0 and 10,8 (1 % solution)
2.2 Water Solubility
Soluble in water, insoluble in ethanol
3. Safety and Handling
3.1 Hazard Codes
3.1 Risk Statements
3.1 Safety Statements
3.1 WGK Germany

2.Hazard identification

2.1 Classification of the substance or mixture

Eye irritation, Category 2

2.2 GHS label elements, including precautionary statements

Signal word


Hazard statement(s)

H319 Causes serious eye irritation

Precautionary statement(s)

P264 Wash ... thoroughly after handling.

P280 Wear protective gloves/protective clothing/eye protection/face protection.


P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.

P337+P313 If eye irritation persists: Get medical advice/attention.





2.3 Other hazards which do not result in classification


5. Other Information
5.0 Merck
5.1 Product description
Potassium pyrophosphate, also known as tetra-sodium pyrophosphate, is made from the melting of di-potassium phosphate which causing it loss of one water molecule. At room temperature, it is as a white crystalline powder or granules and has a strong moisture absorption capability in air and is easily soluble in water but insoluble in ethanol. Its aqueous solution is alkaline and has effect on inhibition of food spoilage and fermentation. The pH of 1% aqueous solution is about 10.5. At about 25 ℃, the solubility of potassium pyrophosphate in 100g of water is 187g. It is hydrolyzed into potassium phosphate in acid or alkaline solution and can form a viscous-like slurry body when being mixed with water. It is mostly used in combination with other condensed phosphates, such as for the preparation of adhesive of ham and sausage in the ratio of 10% potassium pyrophosphate, 10% sodium pyrophosphate, 30% potassium polyphosphate, 30% sodium polyphosphate and 20% sodium metaphosphate. It is commonly used for preventing the generation of struvite in canned fish, preventing the discoloration of canned fruit, increasing the swelling degree of ice cream, the extracting amount of the raw materials of coffee as well as the yield of ham and sausage, enhancing the water holding capacity of fish, improving the taste and yield of noodles, and preventing the aging of cheese. In order to strengthen and smooth the plating layer, the formulation of industrial production of the plating solution is often very complicated. It is previously often applied to cyanide as the complexing agent cyanide for preparing plating solution. However, because of the high toxicity of CN-, it does severe harm to the health of electroplating worker. Moreover, the discharge of CN-of sewage, waste gas also seriously contaminates the environment. So it is currently mainly applied of non-cyanide plating with the complexing agent replacing cyanide being potassium pyrophosphate.
Potassium pyrophosphate
The potassium pyrophosphate has all the properties of other polymeric phosphate and is also similar with sodium pyrophosphate but with a larger solubility and being able to have chelation reaction with the metal ions in alkaline soil and heavy metal ion; It can also form complex with the Ca2 +, Mg2 + in harden water thereby softening the hard water, improving washing ability as well as removing dirt. It can also form a protective film in the surface of metals such as iron, lead, zinc, and aluminum; the pyrophosphate ion (P2O74-) has a strong dispersing capability on the fine and dispersive solids, thus promoting the homogeneous mixing of fine, trace substances. High purity, low iron-type potassium pyrophosphate has a stable pH buffering capacity with ability of long-term maintenance of pH value of the solution.
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5.2 Identification test
Solubility: easily soluble in water but insoluble in ethanol; use (OT-42) method for the determination.
Take 1 mL of 1% sample solution and add silver nitrate test solution (TS-2l0)
5.3 Content Analysis
Accurately weigh 600 mg of sample for being dissolved in 100 mL water contained in 400ml beaker with hydrochloric acid and pH meter for adjusting the pH of the solution to accurately 3.8. Add 50 mL of 12.5% zinc sulfate solution (125g ZnSO4 7H2O is dissolved in water and be diluted to 1000ml; filter, adjust to pH3.8) and place for 2min. Use 0.1mol/L sodium hydroxide for titrating free acid to pH3.8. Upon being close to the end, after each addition of sodium hydroxide, we should wait for the precipitation of zinc hydroxide before further dissolution. Each ml of 0.1 mol/L sodium is equivalent to 16.52 mg of potassium pyrophosphate (K4P2O7).
5.4 Toxicity
ADI 0~70mg/k (the total amount of phosphorus calculated from phosphate; FAO/WHO, 2001).
It may cause kidney stones in large doses.
Adl 0~70 mg/kg (in terms of phosphorus); According to the provision of the FAO/WHO (1984): for the processed cheese, the total phosphate is 9 g/kg (in terms of phosphorus); luncheon meat: 3 g/kg (base on P2 () 5 meter); frozen shrimp or prawns: 5 g/kg (based on P2 () 5 meter); cooked meat 3 g/kg (based on anhydrous matter).
5.5 Limited use
GB 2760-96: Meat 1g/kg; fruit and vegetable peeling GMP.
FAO/WHO (1984:, g/kg): instant broth, soup, total phosphate: 1000mg/kg (in term of P2O5); total phosphate of processed cheese: 9 (in terms of phosphorus); luncheon meat: 3 (in term of P2O5); quick-freeze weever, perch, plaice, Atlantic cod, haddock, hake, shrimp or prawn: 5 (in term of P2O5); cooked pig toreshank , cooked ham, and cooked minced meat: 3 (based on anhydrous matter).
5.6 Chemical Properties
It is white powder or lumps with the relative density being 2.534 and the melting point being 1109 ℃. It is soluble in water but insoluble in ethanol. Its aqueous solution is alkaline. It solubility of 25 ℃ in 100 g of water is 187 g. The pH of aqueous solution at a concentration of 1% = 10.2. Potassium pyrophosphate has all the properties of all the kinds of other condensed phosphates.
5.7 Uses
It is mainly for applied to non-cyanide electroplating for being used as the complexing agent for replacement of sodium cyanide. It is also be used as a plating pretreatment agent and pyrophosphate plating solution. It can also be used as the components for formulation of clothing detergent, metal surface cleaning agent and bottle detergent as well as the additive used in various kinds of detergents. It can also be used as the clay dispersant in the field of the ceramic industry, the dispersant and buffer for pigment and dye. Bleaching and dyeing industry can use it for the removal of the small amount of ferric ion in water for improving the quality of dyeing.
It can be used for non-cyanide electroplating, dyeing, refining clay and other.
It can be used as analysis agent, the stabilizer of hydrogen peroxide as well as the filler of soap.
It is used as an emulsifier, texturizing agent, and chelating agent in the food industry. It can also be used as the raw material for preparation of pasta-purpose alkaline water. t is commonly used for preventing the generation of struvite in canned fish, preventing the discoloration of canned fruit, increasing the swelling degree of ice cream, the extracting amount of the raw materials of coffee as well as the yield of ham and sausage, enhancing the water holding capacity of fish, improving the taste and yield of noodles, and preventing the aging of cheese.
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5.8 Production method
1. The neutralization and calcination method( the ratio of usage amount of raw materials is 1 mol of phosphate and 2 mol of potassium hydroxide): add 30% food-grade phosphoric acid into the neutralizer and the slowly stir and add food grade potassium hydroxide solution for neutralizing reaction for which the pH is suitable for maintained at 8.4; Heat the solution after the completion of the reaction and further add active carbon for decolorization; filter to remove the insoluble matters and the clarified filtrate was further heated to 120~124 ℃ for evaporative concentration; the precipitate will be separated out after cooling to below 20 ℃; centrifuge for separation to obtain trihydrate-di-potassium phosphate and heat to 120~130 ℃ for removing crystal water to generate anhydrous di-potassium hydrogen phosphate; add it to a calciner for being calcined at 500~600 ℃ for polymerization and the edible potassium pyrophosphate is obtained after cooling. The reaction process is as following:
H3PO4 + 2KOH → K2HPO4 + 2H2O
2K2HPO4 [△] → K4P2O7 + H2O
Have the resulting finished products of potassium pyrophosphate reacted with 0.1 mol/L silver nitrate, and when the reaction solution yields no orthophosphate precipitate of yellow color, the product is qualified.
2. Put 203 kg of potassium hydroxide into the dissolving tank; add water to generate a 48% aqueous potassium hydroxide solution. Put it into the kettle and stir and slowly add drop wise of 85% phosphoric acid for salting reaction. When the added phosphoric acid reaches 100 kg, take one drop of liquid material and add to the white porcelain plate; further add 1 drop of water for dilution and measure the pH using accurate test paper. Stop dropping phosphoric acid when the pH reaches 8.5 to 9.0. Continue for stirring for 0.5 h, stand, and remove the impurities by filtration. The filtrate was then transferred to vaporize pan for concentration; after reaching the glue dry state, it was further transferred to a coking furnace and subject to coking process at 550~650 ℃. After 2 to 3 hour of coking, sampling for measuring the end point (check with 1% silver nitrate solution to until no yellow silver orthophosphate appears). After the completion of the reaction, cool, crystallize to obtain the finished products.
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5.9 Chemical Properties
White crystalline powder
5.10 Uses
Soap and detergent builder, sequestering agent, peptizing and dispersing agent.
5.11 Uses
Potassium pyrophosphate is mainly used as an emulsifier, quality improver and metal ion chelating agent. It can be found in herbicidal compositions as a spray adjuvant. It is also used as an anionic dispersant in water-based (latex) paints.
5.12 General Description
Potassium tetrapyro phosphate is a whitish-colored powdered solid dissolved in an organic solvent. Potassium pyrophosphate may be toxic by ingestion. Contact with the substance should be avoided. The solvent may be flammable.
5.13 Air & Water Reactions
Soluble in water.
5.14 Reactivity Profile
Salts, basic, such as POTASSIUM TETRAPYRO PHOSPHATE, are generally soluble in water. The resulting solutions contain moderate concentrations of hydroxide ions and have pH's greater than 7.0. They react as bases to neutralize acids. These neutralizations generate heat, but less or far less than is generated by neutralization of the bases in reactivity group 10 (Bases) and the neutralization of amines. They usually do not react as either oxidizing agents or reducing agents but such behavior is not impossible.
5.15 Health Hazard
Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
5.16 Fire Hazard
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Containers may explode when heated. Runoff may pollute waterways.
6. Question & Answer
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