The potassium chromate is an inorganic compound of formula K 2 CrO 4, characterized by a powerful oxidizing agent be. It is prepared by treating potassium dichromate with potassium hydroxide according to the reaction: K 2 CrO 7 + 2KOH → 2K 2 CrO 4 + H 2 O.
As a compound with a relatively unique profile, potassium chromate has a number of uses in industrial and scientific contexts. However, due to its toxicity, its exposure should be limited (JACOBS, 2015).
Figure 1: Structure of potassium chromate.
Physical and chemical properties
Potassium chromate are orthorhombic crystals with a yellowish color that lack a characteristic aroma and have an unpleasant bitter taste (National Center for Biotechnology Information, 2017).
Figure 2: Structure of potassium chromate.
Its molecular weight is 194.19 g / mol and its density is 2.7320 g / ml. It has a melting point of 968 ° C and a boiling point of 1000 ° C.
The compound is insoluble in alcohol and very soluble in water, being able to dissolve 62.9 grams per 100 ml of solvent at 20 ° C (Royal Society of Chemistry, 2015).
Reactivity and hazards
Oxidizing agents, such as potassium chromate, can react with reducing agents to generate heat and products that can be gaseous (causing pressurization of closed containers).
Products may be capable of additional reactions (such as combustion in air). The chemical reduction of materials in this group can be rapid or even explosive, but often requires initiation (heat, spark, catalyst, addition of a solvent).
Explosive mixtures of inorganic oxidizing agents with reducing agents often remain unchanged for long periods if initiation is avoided. Such systems are typically mixtures of solids, but can involve any combination of physical states. Some inorganic oxidizing agents are metal salts that are soluble in water.
The dissolution decreases but does not cancel the oxidizing power of such materials. Organic compounds, in general, have some reducing power and in principle can react with compounds of this class.
The actual reactivity varies greatly with the identity of the organic compound. Inorganic oxidizing agents can react violently with active metals, cyanides, esters, and thiocyanates.
The compound poses a threat to the environment. Immediate steps must be taken to limit its spread to it. When used anywhere, for any purpose, potassium chromate requires effective containment and disposal to prevent any runoff or leakage into the environment.
Additionally, potassium chromate has the ability to increase the intensity of a fire if the chemical comes into contact with combustible materials. The compound emits toxic chromium fumes when heated (POTASSIUM CHROMATE, 2016).
Potassium chromate is highly corrosive and is a strong oxidizing agent. It mainly affects the nose, throat, and lungs, causing ulcerations, shortness of breath, bronchitis, pneumonia, and asthma, but it can also affect the gastrointestinal tract, liver, kidneys, and immune system.
This substance is a known human carcinogen and is associated with an increased risk of developing lung cancer and sinonasal cavity cancer (Potassium Chromate, 2016).
Its odorless nature becomes problematic when it has been exposed to this chemical due to its toxicity. In many cases, you may not be aware that you have inhaled the potassium chromate.
Additionally, inhaling this chemical poses several risks. Symptoms include nausea, vomiting, abdominal pain, burning sensation, diarrhea, shock, or collapse.
In case of contact with the eyes, the contact lenses should be checked and removed. Then it is necessary to immediately wash the eyes with plenty of water for at least 15 minutes with cold water.
In case of skin contact, the affected area should be rinsed immediately with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Cover irritated skin with an emollient.
Wash clothing and shoes before reuse. If the contact is severe, wash with a disinfectant soap and cover the contaminated skin with an antibacterial cream.
In case of inhalation, the victim should be moved to a cool place. If not breathing, artificial respiration is given.
If the compound is ingested, vomiting should not be induced unless directed by medical personnel. Loosen tight clothing such as a shirt collar, belt, or tie.
In all cases, medical attention should be obtained immediately (Material Safety Data Sheet Potassium chromate, 2013).
Applications
Potassium chromate has a wide variety of industrial uses. In the textile industry, manufacturers use potassium chromate to tan leather and dye garments and fabrics (Dye, 2017).
It also works as an oxidizing agent in industry and in organic synthesis. It is used medically as an external antiseptic or astringent and is present in some veterinary drugs.
Potassium chromate is used as an indicator in the determination of chloride by titration with standard silver nitrate solution. This method is called Mohr's method of chloride determination.
This method relies on the formation of a red silver chromate precipitate at the end point, after all the chloride has precipitated as white silver chloride.
A 5% solution of potassium chromate that has been neutralized with chloride is commonly used. Approximately 1 mL of this indicator should be used per 100 mL of sample volume (RICCA Chemical Company, 2015). The reactions for Mohr's titration are:
Ag + + Cl - → AgCl (white precipitate)
2 Ag + (excess) + CrO 4 2- → Ag 2 CrO 4 (red precipitate at the end point)
References
- Dye, JL (2017, March 1). Potassium (K) CHEMICAL ELEMENT. Recovered from encyclopedia britannica.com.
- JACOBS, J. (2015, August 3). What Is Potassium Chromate Used For? Recovered from livestrong.com.
- Material Safety Data Sheet Potassium chromate. (2013, May 21). Recovered from sciencelab.com.
- National Center for Biotechnology Information. (2017, March 4). PubChem Compound Database; CID = 24597. Retrieved from PubChem.
- Potassium Chromate. (2016, February 27). Recovered from NCIt.
- POTASSIUM CHROMATE. (2016). Recovered from cameochemicals.
- RICCA Chemical Company. (2015). potassium chromate. Recovered from riccachemical.
- Royal Society of Chemistry. (2015). Potassium chromate. Recovered from chemspider.com.