Stannous pyrophosphate, chemical formula Sn2P2O7, molecular weight 411.32, amorphous powder. It is prepared by heating tin (Ⅱ) diphosphate at 350 ~ 400℃.
Production method of stannous pyrophosphate:
In the double decomposition method, stannous chloride and sodium pyrophosphate were dissolved in water, and an appropriate amount of activated carbon was added for decolorization and filtration to obtain a clean solution. Then add water to each solution and adjust to a certain concentration. Sodium pyrophosphate solution was first added to the reactor, and stannous chloride solution was slowly added under agitation for the double decomposition reaction. Control the end point of the reaction so that stannous chloride is not excessive. Chemicalbook tin pyrophosphate precipitate was generated, after standing, the supernatant was removed, water was added and washed under agitation, then the precipitate was standing, the supernatant was removed, repeated several times, and most of the sodium chloride was washed away. The sediment is then dehydrated in a centrifuge, washed with clean water until it is free of chloride ions and dried to produce the finished tin pyrophosphate. Na4P2O7+2SnCl2→Sn2P2O7+4NaC1
Chemical properties: white crystalline or amorphous powder. The relative density is 4.009(16.4℃). Insoluble in water, soluble in concentrated acid. Purpose: Mainly used for tin plating without cyanide plating. Used as a filling agent of toothpaste, slightly dissociated in toothpaste, to prevent dental disease has a certain role. The printing and dyeing industry is used for dyeing, and the ceramic industry is used for refining clay. In the coating industry, appropriate addition can ease the settling rate of the paint filler in the paint and improve the paint performance.