Zinc chromate sample
| IUPAC name
| Other names
Zinc chromate C
|Molar mass||181.403 g/mol|
|Melting point||316 °C (601 °F; 589 K)|
|Boiling point||732 °C (1,350 °F; 1,005 K)|
|3.08 g/100 ml|
|Solubility|| Soluble in ammonia|
Insoluble in organic solvents
|Vapor pressure||~0 mmHg|
|Safety data sheet||Cameo|
|Lethal dose or concentration (LD, LC):|
LD50 (Median dose)
|500 mg/kg (rat, oral)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Zinc chromate, sometimes known by the trade name Zinc Yellow is an inorganic compound with the chemical formula ZnCrO4. It is a lemon-yellow solid sometimes used as a pigment.
Like other chromates, zinc chromate is an oxidizer and may react with certain organic materials.
- ZnCrO4 + 2 NaOH → Na2CrO4 + ZnO + H2O
Zinc chromate most often appears as a dense, odorless, lemon-yellow powder, making it a desirable pigment. Unlike its more toxic counterpart, lead(II) chromate, zinc chromate may degrade in color over time in bright light. Among pigments, however, it is still considered light-stable and is far less toxic than cadmium or lead yellows, making it more desirable than these.
- Na2CrO4 + Zn(NO3)2 → ZnCrO4 + 2 NaNO3
- Na2CrO4 + ZnCl2 → ZnCrO4 + 2 NaCl
- Na2CrO4 + ZnSO4 → ZnCrO4 + 2 Na2SO4
The brightest yellows appear to emerge from slightly acidic solutions at elevated temperature.
- Homemade yellow paint
- Make sodium chromate
Zinc chromate, as with all other zinc compounds, is toxic if consumed, and can lead to zinc poisoning in the body. The hexavalent chromium in zinc chromate is also a potent oxidizer, and has been demonstrated to be carcinogenic. It is best to handle this compound with gloves, although given its insoluble nature, it is unlikely that one would incur harm from anything less than inhaling or eating it. Additionally, it is still far less toxic than other yellow pigments, such as lead(II) chromate or cadmium sulfide.
Zinc chromate is very stable and does not require special storage considerations. A plastic bottle with a proper label and a hazard symbol is a suitable container.
As mentioned above, boiling sodium hydroxide solution leaches zinc chromate, producing relatively harmless zinc oxide and a solution of sodium chromate. The chromate solution can be acidified and reduced with sulfite or ascorbic acid and disposed of.