Southeast Pennsylvania is actually a lowland area consisting of the undulating plain. Into the north and west of this plain are chains of semi-detached and usually rounded hills extending from South Mountain in the west towards the Reading Prong within the east. The flexibility of STPP to forestall mineral interference https://www.tjcyindustrialchem.com/news/what-is-sodium-tripolyphosphate-stpp-used-for.html