The molecular weight of potassium chloride is 74.55.(1) The unit of measurement used to determine this number is atomic mass, or MA for short.(2)
A single unit of atomic mass is defined as one-twelfth of the nucleus of a carbon-12 atom. In other words, just as Greenwich median time in England is the central reference point from which all other time zones extrapolate, the carbon-12 derived unit of measurement is the one used to compare chemical elements at their most microscopic scale. Potassium chloride, roughly speaking, is worth about five and half full atoms of carbon-12.
Potassium Chloride comes in the form of white crystals or powder. Although it is odorless, it can be harmful if swallowed, and may irritate the eyes, skin, and respiratory tract. It has both a high melting (1422 degrees Fahrenheit) and boiling (2732 degrees Fahrenheit) point, and is a very non-volatile substance.
The main use of potassium chloride is as a fertilizer, when it is also sometimes referred to as “muriate of potash.”(3) Various other forms of potassium are also the base of agricultural chemicals; these include potassium nitrate, potassium sulfate, and potassium hydroxide.
The same chemical of potassium chloride is also used for lighter forms of salt or table salt substitutes.(3) Light salt products, which contain about half the calories of normal salt, are usually a blend of salt and potassium chloride. Additives are also used in these products, and they are to be avoided by anyone who has kidney disease or takes any form of medication that includes potassium as an ingredient.
Potassium chloride is also an atomic mass product that can lead to some colorful, inexpensive home experimentation fun.(4) Young scientists can observe the compound as it dissolves into water and then gradually, over time, turns into glowing crystals. This is a very clear, direct example of the actions of water solubility on a rock solid, powder component.
(1) University of Maryland – Potassium Chloride, Retrieved June 16, 2011 from http://www.atmos.umd.edu/~russ/MSDS/potassium_chloride.htm
(2) Sizes.com – Atomic Mass Unit, Retrieved June 16, 2011 from http://www.sizes.com/units/atomic_mass_unit.htm
(3) Michigan State University – N-P-K Fertilizers, Retrieved June 16, 2011, from http://adsabs.harvard.edu/full/1957AuJPh..10..429W
(4) San Angeleno Standard Times – CRAVE: Living Light, Retrieved June 16, 2011 from http://www.gosanangelo.com/news/2011/jun/15/crave-living-light/
(5) YouTube – Potassium Chloride Glowing Crystal, Retrieved June 16, 2011 from http://www.youtube.com/watch?v=aRBlOmLzJFI