pH計因玻璃电極的不对称电位关系,需經常用緩冲液来校正,因而經常备有数值正确的緩冲液,实为准确控制pH所不可缺少的条件。一般易使緩冲液發生变化的因素为: (一) 保藏在瓶中时,因为經常使用,經常开啟,或瓶塞不严,吸收空气中某些气体而变化,因試驗室中常存有NH_3、CO_2、HCl、SO_2、SO_3、NO_2等气体。 (二) 因反复使用多次后倒回原瓶,由于該液在測定时帶入的水分、杂質而引起濃度变化。 Because of the asymmetric potential of the glass electrode, the pH meter needs to be constantly calibrated with a buffer, and therefore often has the correct value of buffer, which is an essential condition for accurate pH control. Generally easy to make changes in the buffer as follows: (A) preserved in the bottle, because often used, often open, or cautious, absorbing some of the air and the gas changes, as often exist in the laboratory NH 3, CO 2, HCl, SO 2, SO 3, NO 2 and other gases. (B) due to repeated use after pouring back to the original bottle, due to the liquid into the measurement of moisture, impurities caused concentration changes.