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Common properties of alkalis
Alkalines are all Arrhenius bases and share many properties with other chemicals in this group (Arrhenius bases form hydroxide ions when dissolved in water). Common properties of alkaline aqueous solutions include:
Alkalis are opposite of acids.
Confusion between base and alkali
The terms "base" and "alkali" are often used interchangeably, since most common bases are alkalis. It is common to speak of "measuring the alkalinity of soil" when what is actually meant is the measurement of the pH (base property). In a similar manner, bases that are not alkalis, such as ammonia, are sometimes erroneously referred to as alkaline.
Note that not all or even most salts formed by alkali metals are alkaline; this designation applies only to those salts that are basic.
While most electropositive metal oxides are basic, only the soluble alkali metal and alkaline earth metal oxides can be correctly called alkalis.
This definition of an alkali as a basic salt of an alkali metal or alkaline earth metal does appear to be the most common, based on dictionary definitions , however conflicting definitions of the term alkali do exist. These include:
Most basic salts are alkali salts, of which common examples are:
Soil with a pH value higher than 7.3 is normally referred to as alkaline. This soil property can occur naturally, due to the presence of alkali salts. Although some plants do prefer slightly basic soil (including vegetables like cabbage and fodder like buffalograss), most plants prefer a mildly acidic soil (pH between 6.0 and 6.8), and alkaline soils can cause problems.
In alkali lakes (a type of salt lake), evaporation concentrates the naturally-occurring alkali salts, often forming a crust of mildly-basic salt across a large area.
Examples of alkali lakes:
The word "alkali" is derived from Arabic al qalīy = the calcined ashes, referring to the original source of alkaline substance. Ashes were used in conjunction with animal fat to produce soap, a process known as saponification.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Alkali". A list of authors is available in Wikipedia.|