Potassium chloride detailed information

The chemical compound potassium chloride (KCl) is a metal halide composed of potassium and chlorine. In its pure state it is odorless. It has a white or colorless vitreous crystal, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are either simple cubic or face-centered cubic depending on what atoms are involved. If only potassium or chlorine atoms are considered, then the structured is face-centered cubic. However, both atoms form a crystal with a simple cubic structure: x-ray diffraction analysis will yield a simple cubic structure. Potassium chloride is also commonly known as "Muriate of Potash". Potash varies in color from pink or red to white depending on the mining and recovery process used. White potash, sometimes referred to as soluble potash, is usually higher in analysis and is used primarily for making liquid starter fertilizers. KCl is used in medicine, scientific applications, food processing and in judicial execution through lethal injection. It occurs naturally as the mineral sylvite and in combination with sodium chloride as sylvinite.

Chemical properties
Potassium chloride can react as a source of chloride ion. As with any other soluble ionic chloride, it will precipitate insoluble chloride salts when added to a solution of an appropriate metal ion:


 * KCl(aq) + AgNO3(aq) →  AgCl(s) + KNO3(aq)

Although potassium is more electropositive than sodium, KCl can be reduced to the metal by reaction with metallic sodium at 850 °C because the potassium is removed by distillation (see Le Chatelier's principle):


 * KCl(l) + Na(l) ⇌ NaCl(l) + K(g)

This method is the main method for producing metallic potassium. Electrolysis (used for sodium) fails because of the high solubility of potassium in molten KCl.

As with other compounds containing potassium, KCl in powdered form gives a lilac flame test result.

Biological/Medical properties
Potassium is vital in the human body and oral potassium chloride is the common means to replenish it, although it can also be diluted and given intravenously (of course, in concentrations much lower than those used in executions). It can be used as a salt substitute for food, but due to its weak, bitter, unsalty flavor, it is usually mixed with regular salt, sodium chloride, for this purpose to improve the taste (for example, in Morton® Lite Salt ). Medically it is used in the treatment of hypokalemia and associated conditions, for digitalis poisoning, and as an electrolyte replenisher. Brand names include K-Dur®, Klor-Con®, Micro-K®, and Kaon Cl®. Side effects can include gastrointestinal discomfort including nausea and vomiting, diarrhea and bleeding of the gut. Overdoses cause hyperkalemia which can lead to paresthesia, cardiac conduction blocks, fibrillation, arrhythmias, and sclerosis.

Physical properties
Potassium chloride has a crystalline structure like many other salts. Structure: face-centered cubic. Lattice Constant: roughly 6.3 angstroms.

In chemistry and physics it is a very commonly used as a standard, for example as a calibration standard solution in measuring electrical conductivity of (ionic) solutions, since carefully prepared KCl solutions have well-reproducible and well-repeatable measurable properties.

Precautions
Orally it is toxic in excess; the LD50 is around 2500 mg/kg (meaning that a person weighing 75 kg (165 lb) would have to consume about 190 g (6.7 oz); regular salt is about as toxic). Intravenously this is reduced to just over 100 mg/kg but of more concern are its severe effects on cardiac muscles; high doses can cause cardiac arrest and rapid death. A massive overdose of intravenous potassium chloride is used to stop the heart in execution by lethal injection.