It is observed that the salt content of natural water has a profound influence on the determination of nitrate by the Zn-Cd reduction method. But it is found that when the salinity is greater than 1 %, the rate of re-duction by Zn-Cd becomes constant. 研究了锌-镉法测定天然水中硝酸盐的盐误差,发现水中含盐量对还原率有重大影响,但在盐度为1%以后还原率基本不变;