Bis-tris propane, or 1,3-bis(tris(hydroxymethyl)methylamino)propane, is a chemical substance that is used in buffer solutions. It is a white to off-white crystalline powder that is soluble in water. It has a wide buffering range, from 6 to 9.5 due to its two pKa values which are close in value. This buffer is primarily used in biochemistry and molecular biology.