Sodium tetraphosphate

Sodium Tetraphosphate is a kind of sodium phosphate. It can be used as an effective dispersing agent¹. It can also be used in the manufacturing of detergents that possess the property of sequestration². Appropriate quantities of sodium tetraphosphate can be added to the developer to (1) prevent sludge formation in mixing, storing, or use of the developer, (2) prevent the formation of scum on the film when in the developer, and (3) greatly diminish the rate at which incrustations accumulate on the tank walls, sprockets, and mechanical parts³.

1. https://pubs.geoscienceworld.org/sepm/jsedres/article-abstract/22/4/229/95131
2. https://www.jstor.org/stable/4585627?seq=1#page_scan_tab_contents
3. https://ieeexplore.ieee.org/abstract/document/7252099/

Hexasodium tetraphosphate is formed by careful hydrolysis of sodium tetrametaphosphate (Thilo and Ratz method). A solution of 4.8 g of Na4P4O12 4H2O in 85 ml of hot water is prepared, and after cooling, a solution of 0.8 g of NaOH in some water is added. The mixture is kept over H2SO4 in a vacuum desiccator and placed in an oven at 40°C. The rate of evaporation should be such that after about 100 hours, no less than 8 to 10 ml remains. The solution is then diluted to 30 ml, and acetone is added. The colourless oil formed is dissolved in some water and reprecipitated with acetone.