NH42CrO4

NH42CrO4 refers to ammonium chromate, a simple inorganic salt with the formula (NH4)2CrO4. It consists of ammonium cations (NH4+) and the chromate anion (CrO4^2−). In solid form it appears as yellow crystals and is highly soluble in water, forming clear, colorless to pale yellow solutions. The compound adopts the typical ionic lattice characteristic of many chromate salts and is commonly handled as a laboratory reagent.

Preparation and occurrence: Ammonium chromate can be prepared by neutralizing chromic acid (H2CrO4) or related chromium(VI) oxoanions with ammonium bases such as ammonium hydroxide, yielding (NH4)2CrO4 that crystallizes upon solution cooling. It is typically generated in aqueous media rather than isolated directly from natural sources.

Chemical properties: As a chromium(VI) salt, ammonium chromate is an oxidizing salt and its solutions are basic enough to maintain chromium in the hexavalent state. The chromate anion CrO4^2− is in equilibrium with dichromate (Cr2O7^2−) depending on pH. The compound is moisture-sensitive to some extent and forms hydrates when exposed to humidity.

Uses: Ammonium chromate is used as a laboratory reagent and as an intermediate in the preparation of other chromium(VI) compounds. It has historical relevance in certain pigment and chemical synthesis applications, though its use is limited by toxicity concerns associated with hexavalent chromium.

Safety: Ammonium chromate contains hexavalent chromium, which is toxic and carcinogenic. It can cause irritation to skin, eyes, and the respiratory tract. It should be handled with appropriate personal protective equipment, good laboratory practices, and proper waste disposal to prevent environmental release.