Overview【1】
Trisodium phosphate is also called sodium orthophosphate and commercially known as sodium phosphate. Molecular weight plastic antistatic agent 380.20.
1． Trisodium phosphate can be regarded as a product obtained by using phosphoric acid H3 high temperature resistant inorganic pigment P04 as the matrix and replacing all three hydrogen ions H+ contained in its molecular formula with three metal sodium atoms Na. Because phosphate H3POt is a tribasic acid, its molecular formula has three hydrogen ions that can be replaced by metal elements.
2. Phosphoric acid can directly react with sodium to produce three kinds of sodium salts: When a hydrogen ion in the molecular formula of phosphoric acid is replaced by a metal sodium atom, the first sodium salt is produced, namely sodium dihydrogen phosphate NaH2P04. When there are two hydrogen ions in the phosphoric acid molecular formula and are replaced by two metal sodium atoms, the second sodium salt is generated, namely disodium hydrogen phosphate Na2HPO4. The above two sodium salts are called acid salts because there are hydrogen ions in the molecular formula.
3． When all three hydrogen ions in the phosphoric acid molecular formula are replaced by three sodium atoms, the third sodium salt is generated, also called orthosalt (sodium orthophosphate), that is, trisodium phosphate.
Properties
1． Trisodium phosphate is a white triangular crystalline particle that weathers in the air, 100. C, the water of crystallization is lost. But even at 200.0, the last crystal cannot completely lose water.
2. The solubility of trisodium phosphate in cold water is 28.3% (15.0), and it is easily soluble in hot water to form a strongly alkaline solution (stronger than sodium carbonate solution of the same concentration), because it can partially Adding water decomposes to produce sodium hydroxide, as follows:
3． Trisodium phosphate 1% aqueous solution has a pH value of 12 at room temperature. Because it is too alkaline, it is not an auxiliary ingredient for household synthetic detergents.
4． Trisodium phosphate can be partially decomposed by adding water, so the OH-concentration of hydroxide ions in its solution of the same concentration is not as high as that of caustic soda (sodium hydroxide), so the strong corrosiveness of caustic soda can be avoided. However, its hydroxide ion concentration is indeed much greater than that of soda ash (sodium carbonate). Obviously, its grease-dissolving and cleaning effects are weaker than caustic soda but stronger than soda ash.
Characteristics and performance
Trisodium phosphate is a colorless to white hexagonal crystal. It is soluble in water but insoluble in ethanol. It is almost completely decomposed into disodium hydrogen phosphate and sodium hydroxide in aqueous solution, which is highly alkaline. The pH of 1% aqueous solution is 11.5~12.1. It has the functions of maintaining moisture, emulsifying, complexing metal ions, improving tone and color, adjusting pH and tissue structure.
Toxicity【2】
Oral LD in prairie dogs. >2 g/kg. ADI is 0 ~ 70 mg/kg (referring to the total amount in food and food additives, with phosphorus juice. And pay attention to the balance with Ca). Phosphorus is an important element for all living organisms and is often used by organisms in the form of phosphate. It is an indispensable part in energy transmission, human tissues (such as teeth, bones and some enzymes), and metabolism of carbohydrates, fats and proteins. Therefore, phosphate is often used as a nutritional fortifier in food. Under normal dosage, it will not cause an imbalance of phosphorus and calcium. However, if used in excessive dosage, it will combine with calcium in the intestine to form calcium orthophosphate that is insoluble in water, thus reducing the Calcium absorption. The FDA lists sodium iphosphate as a food additive generally recognized as safe (GRAS).
Use 【2】
According to the “National Food Safety Standard Food Additive Usage Standard” (GB 2760-2014), trisodium phosphate is used in fat emulsification other than milk and dairy products, cream, water-oil fat emulsification products, and water-oil fat emulsification products. Products (including mixed and flavored fat emulsions), frozen drinks (other than edible ice), canned vegetables, cooked nuts and seeds (fried nuts and seeds only), cocoa products, chocolate and chocolate products, and confectionery , wheat flour and its products, wheat flour, wet and raw flour products (such as noodles, dumpling wrappers, wonton wrappers, siomai wrappers), batter (such as batter for fish and poultry), breading flour, frying powder, multigrain flour, Edible starch, ready-to-eat cereals (including rolled oats or oatmeal), prepared meat products, cooked meat products, frozen aquatic products, frozen surimi products (including fish balls, etc.), heat-coagulated egg products (such as egg yolk cheese, preserved egg sausage ), beverages (except packaged drinking water), jelly, the maximum usage amount is 5 g/kg; when used for milk powder, cream powder and flavored syrup, the maximum usage amount is 10.0 g/kg; for rice noodles (including glutinous rice balls) powder), cereal and starch desserts (such as rice pudding, tapioca pudding, only canned cereal desserts), pre-made aquatic products (semi-finished products), canned aquatic products, the maximum usage amount is 1. o g/kg; used for compound seasonings, the maximum usage amount is 20. o g/kg; used for other solid compound seasonings (only for instant wet noodle seasoning packets), the maximum usage amount is 80.0 g/kg; used for puffed foods and cooked nuts and seeds (only for fried nuts) and seeds), the maximum usage amount is 2.0 g/kg; when used in other oils or oil products (only non-dairy fat powder), the maximum usage amount is 20 g/kg; when used in processed cheese, the maximum usage amount is 20 g/kg The amount is 15.0 g/kg; used for canned cereals and other cereal products (only frozen French fries, frozen hash browns, frozen mashed potatoes, frozen sweet potato mashed). The maximum usage amount is 1.59/kg. Trisodium phosphate can be used alone or mixed, calculated as phosphate (P03).
Preparation【3】
1． Phosphoric acid extraction method
React phosphate rock powder and sulfuric acid to obtain extracted phosphoric acid, add��Add an appropriate amount of washing water, dilute it until the content of phosphorus pentoxide in the solution is 18% to 20%, and heat it to 85°C. C. Slowly add 30-350% sodium carbonate solution under stirring to carry out neutralization reaction to make the pH value = 8-8.4. Then add trisodium phosphate mother liquor to make the phosphorus pentoxide content in the solution <12%. Keep warm for 15~20rain, filter, evaporate and concentrate to 24~2586. Add liquid caustic soda to bring the sodium/phosphorus ratio to 3.24-3.26. After cooling and crystallization, centrifugal separation and air flow drying, the finished product of trisodium phosphate dodecahydrate is obtained. The reaction formula is as follows:
2. Thermal phosphoric acid method
Add hot phosphoric acid into the reactor, and slowly add liquid caustic soda under stirring to perform a neutralization reaction to generate trisodium phosphate. After cooling and crystallization, centrifugal separation, and drying, the finished product trisodium phosphate is obtained. The reaction formula is as follows:
Synthetic route【4】
References
[1] Compiled by Liu Zhengchao, Dyeing Agents Revised Edition (Volume 2), Textile Industry Press, July 1965, 1st edition, page 90
[2] Editor-in-Chief Hao Liping, Food Additives 3rd Edition, China Agricultural University Press, 2016.07, page 231
[3] Editor-in-chief Wen Huiliang, Chemical Additives, Jiangxi Science and Technology Press, 2009.12, page 305
[4] Compiled by Song Yelin, Practical Handbook of Boiler Water Treatment, Sinopec Press, 2007.2, page 359
