Chromic acid
Dichromic acid (left) and chromic acid (right) | |
| Names | |
|---|---|
| IUPAC names
Chromic acid Dichromic acid | |
| Systematic IUPAC name
Dihydroxidodioxidochromium | |
| Other names
Chromic(VI) acid Tetraoxochromic acid | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.028.910 |
| EC Number |
|
| 25982 | |
PubChem CID |
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| UNII | |
| UN number | 1755 1463 |
CompTox Dashboard (EPA) |
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| Properties | |
| H2CrO4 (chromic acid) H2Cr2O7 (dichromic acid) | |
| Molar mass | 118.008 g/mol (chromic acid) 218.001 g/mol (dichromic acid) |
| Appearance | Dark purplish-red sand-like crystalline solid or powder |
| Odor | Odorless |
| Density | 1.201 g/cm3 |
| Melting point | 197 °C (387 °F; 470 K) |
| Boiling point | 250 °C (482 °F; 523 K) (decomposes) |
| 169 g/(100 mL) | |
| Acidity (pKa) | −0.8 to 1.6 (chromic acid) |
| Conjugate base | Chromate and dichromate |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
highly toxic, carcinogen, corrosive |
| GHS labelling: | |
| Danger | |
| H271, H300+H310+H330, H301, H314, H317, H334, H340, H341, H350, H361, H372, H410 | |
| P201, P202, P210, P220, P221, P260, P261, P262, P264, P270, P271, P272, P273, P280, P281, P283, P284, P285, P301+P310, P301+P330+P331, P302+P350, P302+P352, P303+P361+P353, P304+P340, P304+P341, P305+P351+P338, P306+P360, P308+P313, P310, P314, P320, P321, P322, P330, P333+P313, P342+P311, P361, P363, P370+P378, P371+P380+P375, P391, P403+P233, P405, P501 | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
51.9 mg/kg (H2CrO4·2Na, rat, oral) |
| NIOSH (US health exposure limits): | |
PEL (Permissible) |
TWA 0.005 mg/m3 |
REL (Recommended) |
TWA 0.001 mg Cr(VI)/m3 |
IDLH (Immediate danger) |
15 mg Cr(VI)/m3 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |
Chromic acid is a chemical compound with the chemical formula H2CrO4. It is also a jargon for a solution formed by the addition of sulfuric acid to aqueous solutions of dichromate. It consists at least in part of chromium trioxide.
The term "chromic acid" is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of chromic acid may be used as a cleaning mixture for glass. Chromic acid may also refer to the molecular species, H2CrO4 of which the trioxide is the anhydride. Chromic acid features chromium in an oxidation state of +6 (and a valence of VI or 6). It is a strong and corrosive oxidizing agent and a moderate carcinogen.