Nessler reagent

Ness·ler re·a·gent

(nes'lĕr), a solution of potassium hydroxide, mercuric iodide, and potassium iodide; it yields a yellow color with ammonia (a brown precipitate with larger amounts) that can be used for quantitative assay.

Nessler,

A., German chemist, 1827-1905. Nessler reagent - a solution of potassium hydroxide, mercuric iodide, and potassium iodide.