Chlorine Chloride - Midwest Laboratories

Chlorine (Cl2): Greenish-yellow, diatomic gas; suffocating odor, highly reactive; The raw gas is marketed in the
form of gas over liquid compressed into steel cylinders. Chlorine is soluble in water forming aqueous chlorine. It is
soluble in alkalis as in sodium hypochlorite solution, which is household bleach.
Chloride (Cl-): The negative charged ionic form of chlorine. A common anion found abundantly in nature. It
associates with almost all cations forming neutral salts such as sodium chloride (table salt), potassium chloride
(muriate of potash), calcium chloride and many other common salts.
A few facts about chloride and chlorine:
• Chlorine dissolved in water or alkali is very loosely associated and when not stored in a closed container or under
pressure, all the chlorine eventually dissipates as a gas. This gradual volatile-zation is evident in the free chlorine
odor associated with household bleach or swimming pools.
Chlorinated drinking water left standing at room temperature in an open container will lose all of its chlorine in an
8-12 hour period.
Chloride does not convert to chlorine in nature. Chloride is an exceptionally stable, odorless and colorless ion.
Chloride is not toxic. Any damage to plants or animals is due to the properties of the salt when present in
excessive quantities, and is not a result of toxicity of the chloride ion.
You will sometimes see the term chlorine in literature when referring to chloride. The element Cl on the periodic
chart is named chlorine. Therefore, when chloride is referred to as a quantity of the element, it is called chlorine.
This is technically correct, however confusing, as they are really referring to the chloride ion .
It is not practical to ask the laboratory to analyze for chlorine in plants, soils, fertilizer or waters. Any chlorine
present in these matrices would dissipate before it could be sampled and tested. The exception would be free
chlorine in water tested on site within an hour or two after sampling.
Chlorine results are always reported by our laboratory as free chlorine. All chloride results are reported as
Chloride is considered an essential plant nutrient necessary for photosynthesis; chloride has also been proven
essential in disease suppression in plants.
High levels of salt (NaCl) in the soil can result in plant toxicity. All plants and animals have various chloride
requirements and tolerances.
Soils with high chloride levels can be managed by using soil amendments, improving drainage and utilizing crops
with high salt tolerance.
Chlorine is a highly reactive gas. However, when chlorine reacts with other compounds, the reaction does not
always or necessarily produce the ion of chloride. For example: Chlorine added to soil as a fumagant produces
very little chloride. It either dissipates as chlorine gas or produces other compounds from the reaction with the
soil matrix other than the chloride ion.
Potassium chloride is a common source of potassium in fertilizers. Regardless of the source, all potassium in
fertilizer is labeled as potassium oxide or potash. This fact can make fertilizer labeling confusing. For example:
Muriate of potash which is 99% potassium chloride (KCl) is labeled 62% potash (K 2O).
Chlorine can react with organic matter to produce highly toxic compounds called chlorinated hydrocarbons.
Chloride will not react to form these types of compounds.