Melzer's reagent， also known as Melzer's solution or simply Melzer， was invented in 1924 by mycologist Václav Melzer. It is composed of chloral hydrate， potassium iodide， iodine， and deionized water. This reagent plays a crucial role in the analysis of spore ornamentation or starch in entire spores， and is commonly used to assist in the identification of fungi. When using Melzer's reagent， simply drop it onto fungal tissue or cellular samples， then observe the color change to determine the type of starch reaction.

The reaction of Melzer's reagent occurs almost instantaneously， though in some cases it may take up to 20 minutes to observe the reaction phenomenon. The compounds that constitute Melzer's reagent have multiple functions. Chloral hydrate enhances sample translucency， serving to bleach and improve the transparency of various dark-colored substances. Potassium iodide is used to increase iodine solubility， as iodine is only semi-soluble in water without it. Iodine is considered the primary staining agent in Melzer's reagent， reacting with starch-like polysaccharides in the cell walls of starch-containing substances. However， the specific reaction mechanism remains unclear. This reagent is exclusively used in scientific research and is not suitable for clinical diagnosis or other applications.