Sodium Tripolyphosphate → Pyrophosphate

Participants

Reaction Conditions

Reaction Steps

The industrially important pentasodium triphosphate, Na5P3O10 (sodium tripolyphosphate), is a nonhygroscopic, white, water-soluble salt which is anhydrous or crystallizes with 6H2O and has the general formula NaO—[P(O)(ONa)—O]n—Na where n=3. About 17 g of the anhydrous salt dissolve in 100 g of water at room temperature, at 60° about 20 g, at 100° around 32 g; after heating the solution at 100° C. for two hours, about 8% orthophosphate and 15% diphosphate are produced by hydrolysis. For the preparation of pentasodium triphosphate, phosphoric acid is reacted with sodium carbonate solution or sodium hydroxide solution in stoichiometric ratio and the solution is dewatered by spraying. In a similar way to Graham's salt and sodium diphosphate, pentasodium triphosphate dissolves numerous insoluble metal compounds (including lime soaps, etc). Pentapotassium triphosphate, K5P3O10 (potassium tripolyphosphate), is commercialized, for example, in the form of a 50% strength by weight solution (>23% P2O5, 25% K2O). The potassium polyphosphates find broad application in the laundry detergents and cleaning products industry. There also exist sodium potassium tripolyphosphates, which may likewise be used for the purposes of the present invention. These are formed, for example, when sodium trimetaphosphate is hydrolyzed with KOH:

Provenance & Evidence