Melzer's Reagent

Melzer's Reagent (also known as Melzer's solution) is a chemical reagent used by mycologists to assist with identifying fungus specimens.

It consists of a combination of iodine with chloral hydrate, potassium iodide, and water. One formulation calls for 20 g chloral hydrate; 20 mL distilled water, 0.5 g iodine, and 1.5 g potassium iodide (Miller and Miller, 2006).

Three reactions to Melzer's reagent are possible:
 * tissues turn blue. This is called an amyloid reaction.
 * tissues turn reddish-brown, a dextrinoid reaction.
 * tissues do not change color, or become faintly yellow-brown, a negative reaction.

The substance is toxic to humans.