Buffers
Buffers are chemicals that minimize changes to the pH of a solution when acids or bases are added. (Think of them as pH insulators -- they slow any change in pH). Buffers can take up extra hydrogen ions, or release them when the number of H+ ions in the solution drops.
We investigated the buffering properties of four solutions in lab: water, sodium chloride, milk, and sodium phosphate. The solutions with the least pH change were the best buffers: milk and sodium phosphate.