He Potassium chromate Is an inorganic compound of formula K 2 CrO 4 , Which is characterized as being a powerful oxidizing agent.
It is prepared by treating the potassium dichromate with potassium hydroxide according to the reaction.
K 2 CrO 7 + 2KOH → 2K 2 CrO 4 + H 2 OR
In solution, the behavior of potassium and sodium dichromate is very similar.
Figure 1: Structure of potassium chromate.
As a compound with a relatively unique profile, potassium chromate has a number of uses in industrial and scientific contexts. However, because of its toxicity, you should limit your exposure to potassium chromate (JACOBS, 2015).
Physical and chemical properties
Potassium chromate are orthorhombic crystals of 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, where 62.9 grams per 100 ml of solvent can be dissolved at 20 ° C (Royal Society Of Chemistry, 2015).
Reactivity and hazards
Oxidizing agents, such as potassium chromate, may react with the reducing agents to generate heat and products which may be gaseous (causing pressurization of the closed containers).
The products may be capable of additional reactions (such as combustion in the air). The chemical reduction of the materials in this group can be rapid or even explosive, but often requires initiation (heat, spark, catalyst, addition of a solvent).
Explosive blends of inorganic oxidizing agents with reducing agents often remain unchanged for long periods if initiation is avoided. Such systems are typically solid mixtures, but may involve any combination of physical states. Some inorganic oxidizing agents are salts of metals which are soluble in water.
The solution decreases but does not negate the oxidizing power of such materials. The 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 measures should 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 in the environment.
In addition, 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 on heating (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 cancer of the nasosinusal cavity (Potassium Chromate, 2016).
Its odorless nature becomes problematic when it has been exposed to this chemical because of its toxicity. In many cases, you may not realize that you have inhaled the potassium chromate. In addition, inhalation of this chemical poses several risks. Symptoms include nausea, vomiting, abdominal pain, burning sensation, diarrhea, shock or collapse.
In case of contact with eyes, contact lenses should be checked and removed. Then immediately flush eyes with copious amounts of water for at least 15 minutes with cold water.
In case of contact with the skin, 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 skin contaminated with an anti-bacterial cream
In case of inhalation, remove to fresh air. If not breathing, give artificial respiration.
If the compound is ingested, do not induce vomiting unless directed to do so 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 enjoys 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 functions as an oxidizing agent in industry and in organic synthesis. It is used medically as an external or astringent antiseptic 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 the Mohr method of chloride determination.
This method is based on the formation of a red precipitate of silver chromate at the end point, after which all the chloride has precipitated as white silver chloride.
A 5% solution of potassium chromate which has been neutralized with chloride is commonly used. Approximately 1 mL of this indicator should be used per 100 mL sample volume (RICCA Chemical Company, 2015). Reactions for Mohr 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, J.L. (2017, March 1). Potassium (K) CHEMICAL ELEMENT. Retrieved from encyclopedia britannica.com.
- JACOBS, J. (2015, August 3). What Is Potassium Chromate Used For? Retrieved from livestrong.com.
- Material Safety Data Sheet Potassium chromate. (2013, May 21). Retrieved from sciencelab.com.
- National Center for Biotechnology Information. (2017, March 4). PubChem Compound Database; CID = 24597. Recovered from PubChem.
- Potassium Chromate. (2016, February 27). Retrieved 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.