Potassium dichromate
[CAS# 7778-50-9]

Identification

• Classification: API >> Synthetic anti-infective drugs >> Disinfectant antiseptic
• Name: Potassium dichromate
• Synonyms: Dipotassium oxido-(oxido(dioxo)chromio)oxy-dioxochromium
• Molecular Formula: K₂Cr₂O₇
• Molecular Weight: 294.18
• CAS Registry Number: 7778-50-9
• EC Number: 231-906-6
• SMILES: [O-][Cr](=O)(=O)O[Cr](=O)(=O)[O-].[K+].[K+]

Properties

• Density: 2.676
• Melting point: 398 °C
• Boiling point: 500 °C
• Water solubility: 125 g/L (20 °C)

Safety Data

• Hazard Symbols: GHS03;GHS06;GHS07;GHS08;GHS05;GHS09 Danger
• Risk Statements: H272-H350-H340-H360FD-H330-H301-H312-H372-H314-H334-H317-H400-H410
• Safety Statements: P203-P210-P220-P233-P260-P261-P264-P264+P265-P270-P271-P272-P273-P280-P284-P301+P316-P301+P330+P331-P302+P352-P302+P361+P354-P304+P340-P305+P354+P338-P316-P317-P318-P319-P320-P321-P330-P333+P317-P342+P316-P362+P364-P363-P370+P378-P391-P403-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Respiratory sensitization	Resp. Sens.	1	H334
Skin corrosion	Skin Corr.	1B	H314
Skin sensitization	Skin Sens.	1	H317
Acute toxicity	Acute Tox.	3	H301
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Germ cell mutagenicity	Muta.	1B	H340
Carcinogenicity	Carc.	1B	H350
Oxidising solids	Ox. Sol.	2	H272
Acute toxicity	Acute Tox.	2	H330
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Acute toxicity	Acute Tox.	4	H312
Reproductive toxicity	Repr.	1B	H360
Serious eye damage	Eye Dam.	1	H318
Reproductive toxicity	Repr.	1B	H360FD
Acute toxicity	Acute Tox.	1	H330
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Carcinogenicity	Carc.	1B	H351
Germ cell mutagenicity	Muta.	1B	H341
Acute toxicity	Acute Tox.	2	H300
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	1	H310
Carcinogenicity	Carc.	1A	H350
Skin corrosion	Skin Corr.	1C	H314
Specific target organ toxicity - single exposure	STOT SE	1	H370
Specific target organ toxicity - single exposure	STOT SE	1	H335
Reproductive toxicity	Repr.	1B	H360FD

• Transport Information: UN 1479

Discovery and Applications

Potassium dichromate, with the chemical formula K2Cr2O7, is a bright orange, crystalline compound primarily used as an oxidizing agent in various chemical processes. It was first discovered in the early 19th century, although its use can be traced back even further to the 18th century when chromium compounds were identified. The isolation of potassium dichromate from chromate ore is credited to the French chemist Louis Nicolas Vauquelin in the late 1700s. It gained prominence in the 1830s when it was first commercially produced by heating chromite ore with potassium carbonate and sulfuric acid.

The primary application of potassium dichromate lies in its role as a strong oxidizing agent in organic chemistry. It is widely utilized in various chemical reactions, including the oxidation of alcohols to aldehydes and ketones, and the conversion of primary alcohols to carboxylic acids. Its reactivity makes it an essential reagent in many laboratory procedures and industrial processes.

In addition to its chemical applications, potassium dichromate is also used in the tanning of leather and in the production of dyes and pigments. The compound imparts a distinctive color to leather and textiles, enhancing their aesthetic appeal. Furthermore, potassium dichromate is employed in the manufacture of chromic acid, which is used in electroplating and the production of chromium-based compounds.

Despite its utility, potassium dichromate poses significant health and environmental risks. It is classified as a carcinogen and can cause severe respiratory issues, skin irritation, and other health problems upon exposure. As a result, stringent regulations govern its use and disposal. In recent years, the search for safer alternatives has increased, particularly in industries where potassium dichromate was previously a standard reagent.

The use of potassium dichromate in analytical chemistry is another important application. It is employed as a standard for the determination of various substances, including iron and phosphates, in water analysis. Its ability to act as an oxidizing agent allows for precise quantitative analysis, contributing to environmental monitoring and quality control in industrial processes.

In conclusion, potassium dichromate is a historically significant compound with diverse applications in chemistry, leather tanning, and analytical methods. While it remains a valuable reagent due to its strong oxidizing properties, awareness of its health and environmental risks has prompted efforts to find safer alternatives in various industries.

References

1984. Concentration-dependent effects of potassium dichromate on the cell cycle. Cytometry, 5(5).
DOI: 10.1002/cyto.990050508

2007. Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions. Geochemical Transactions, 8(4).
DOI: 10.1186/1467-4866-8-4

1998. Hsp72 mRNA production in cultured human cells submitted to nonlethal aggression by heat, ethanol, or propanol. Application to the detection of low concentrations of chromium(VI) (potassium dichromate). Cell Biology and Toxicology, 14(2).
DOI: 10.1023/a:1007464421018