席夫试验（Schiff test），由德国化学家雨果·席夫（Hugo Schiff）发明的一种检验醛类的方法，与醛类反应会呈现紫红色。

Schiff试剂由碱性品红与亚硫酸氢钠两种主要的化合物组成。

碱性品红大多是由盐酸蔷薇苯胺（C₁₉H₁₈N₃Cl）与盐酸副蔷薇苯胺的混合物所组成。它与亚硫酸混合后脱去水分子产生加成反应即变无色。

无色的碱性品红-亚硫酸加成物再与醛作用后，起初亦生成无色化合物，但接着失去与碳结合的磺酸基分子而成醌型结构的化合物，呈现出紫红色。此紫色产物加硫酸后褪色，但甲醛与希夫试剂生成的紫红色产物加硫酸后颜色不消失，故可利用此方法区分甲醛与其他醛类。日常生活中可作为检验假酒的试剂。

The Schiff test is an early organic chemistry name reaction developed by Hugo Schiff, and is a relatively general chemical test for detection of many organic aldehydes that has also found use in the staining of biological tissues. The Schiff reagent is the reaction product of a dye formulation such as fuchsin and sodium bisulfite; pararosaniline (which lacks an aromatic methyl group) and new fuchsin (which is uniformly mono-methylated ortho to the dye's amine functionalities) are dye alternatives with comparable detection chemistry.