Potassium chloride (poe-TAS-ee-yum KLOR-ide) occurs as a white or colorless crystalline solid or powder. It is odorless, but has a strong saline (salty) taste. It occurs naturally in the minerals sylvite, carnallite, kainite, and sylvinite. It also occurs in sea water at a concentration of about 0.076 percent (grams per milliliter of solution). Potassium chloride is the most abundant compound of the element potassium and has the greatest number of applications of any salt of potassium. By far the most important application of potassium chloride is in the manufacture of fertilizers.
Potassium muriate; muriate of potash
Binary salt (inorganic)
Not applicable; sublimes at about 1500°C (2700°F)
Very soluble in water; slightly soluble in ethyl alcohol, and insoluble in ether, acetone, and other organic solvents
HOW IT IS MADE
All of the major sources of potassium chloride have their origin in sea water. Sea water is a solution of a number of salts dissolved in water. The most important of those salts are sodium chloride (about 2.3 percent), magnesium chloride (about 0.5 percent), sodium sulfate (about 0.4 percent), calcium chloride (about 0.1 percent) and potassium chloride (about 0.07 percent). When large bodies of sea water dry up, they leave behind complex mixtures of minerals consisting of these salts. Over millions of years, huge deposits of these minerals have been buried under the land. In the United States, sea salt deposits are found in New Mexico, Texas, California, and Michigan.
Any one of the salts present in a sea salt deposit—including potassium chloride—can be extracted by a common procedure. The minerals that make up the deposit are crushed and dissolved in hot water. The solution is then allowed to cool very slowly. As it cools, each of the dissolved salts crystallizes out at a specific temperature, is removed from the solution, and is purified. Since potassium chloride is much more soluble in hot water than in cold water, it crystallizes out after other salts have been removed.
The majority of potassium chloride in the United States is now extracted by a lengthy process that also begins with the crushing of natural ores, such as sylvite and carnalite. The solid mixture is then cleaned and purified before being treated with a flotation agent, usually some type of amine. A flotation agent is a material that coats the desired compound, such as potassium chloride, and allows it to float to the surface of the reaction chamber, like the soap suds that float on top of a washing machine. An amine is an organic compound that contains the nitrogen, usually as the -NH2group. The amine-coated potassium chloride is skimmed off the top of the reaction mixture, purified, and prepared in some crystalline or powder form.
COMMON USES AND POTENTIAL HAZARDS
Potassium chloride is present in some foods in small amounts. The compound is also used as a food additive to increase the acidity and to stabilize, thicken, or soften some food products, such as jams and jellies and preserves that are artificially sweetened. Many infant formulas also contain potassium chloride. Potassium chloride is also used as a nutrient for yeast cultures and in making beer. The compound is used as a salt substitute for people who are on low-salt (meaning low-sodium) diets. Some brand names of these products are LoSalt®, Reheis Less Salt Blend®, and Morton® Lite Salt®.
- One use of potassium chloride is as a lethal injection for prisoners who have been given the death penalty. The chemical interferes with normal heart function and causes a heart attack within five to about eighteen minutes after injection. Thirty-four of the United States prescribe death by lethal injection for prisoners who have been convicted of murder.
The largest application of potassium chloride is in the production of fertilizers. More than ninety percent of the potassium chloride produced in the United States is used for that purpose. The compound provides the potassium plants need to stay healthy and grow normally. It is one of three macronutrients—substances needed in relatively large amounts—for normal growth. The other two macronutrients are phosphorus and nitrogen. Smaller amounts of potassium chloride are used in the production of other potassium compounds, in photography, and in chemical research applications.
FOR FURTHER INFORMATION
Benfell, Carol. "Routine but Deadly Drug: Potassium Chloride Has a Jekyll and Hyde Personality." American Iatrogenic Association. http://www.iatrogenic.org/potchlor.html (accessed on October 31, 2005).
"Potassium Chloride." MedicineNet.com. http://www.medicinenet.com/potassium_chloride/article.htm (accessed on October 31, 2005).
"Potassium Chloride." University of Maryland Medical Center. http://www.umm.edu/altmed/ConsDrugs/PotassiumChloridecd.html (accessed on October 31, 2005).