buffering agent
A substance that stabilizes pH in a solution; used in chemistry and related fields.
この実験では、緩衝剤としてリン酸塩を使います。
In this experiment, we use phosphate as a buffering agent.
Compound of 緩衝 (buffer, cushioning) and 剤 (agent, preparation). The exact historical derivation is uncertain; the term is a modern technical coinage.