Editing PH indicator (section)

== Naturally occurring pH indicators ==
Many plants or plant parts contain chemicals from the naturally colored [[anthocyanin]] family of compounds. They are red in acidic solutions and blue in basic. Anthocyanins can be extracted with water or other solvents from a multitude of colored plants and plant parts, including from leaves ([[red cabbage]]); flowers ([[Pelargonium|geranium]], [[poppy]], or [[rose]] petals); berries ([[blueberry|blueberries]], [[blackcurrant]]); and stems ([[rhubarb]]). Extracting anthocyanins from household plants, especially [[red cabbage]], to form a crude pH indicator is a popular introductory chemistry demonstration.

[[Litmus]], used by alchemists in the Middle Ages and still readily available, is a naturally occurring pH indicator made from a mixture of [[lichen]] species, particularly ''[[Roccella tinctoria]]''. The word ''litmus'' is literally from 'colored moss' in [[Old Norse]] (see [[Litr]]). The color changes between red in acid solutions and blue in alkalis. The term 'litmus test' has become a widely used metaphor for any test that purports to distinguish authoritatively between alternatives.

''[[Hydrangea macrophylla]]'' flowers can change color depending on soil acidity. In acid soils, chemical reactions occur in the soil that make [[aluminium]] available to these plants, turning the flowers blue. In alkaline soils, these reactions cannot occur and therefore aluminium is not taken up by the plant. As a result, the flowers remain pink.

Another natural pH indicator is the spice [[Turmeric#Indicator|turmeric]]. It turns yellow when exposed to [[acids]] and reddish brown when in presence of an [[alkalis]]. 

{| class="wikitable"
! Indicator
! Low pH color
! High pH color
|-
|[[Hydrangea]] flowers
| style="background:blue; color:white" | blue
| style="background:fuchsia; color:white" | pink to purple
|-
|[[Anthocyanins]]
| style="background:red; color:white" | red
| style="background:blue; color:white" | blue
|-
|[[Litmus]]
| style="background:red; color:white" | red
| style="background:blue; color:white" | blue
|-
|[[Turmeric]]
| style="background:yellow"|yellow
| style="background:brown; color:white" |reddish brown
|}
<gallery mode="packed" heights="120">
File:Blue Hydrangea.jpg|Hydrangea in acid soil
File:Hortensiapink.JPG|Hydrangea in alkaline soil
File:Indicateur chou rouge.jpg|A gradient of red cabbage extract pH indicator from acidic solution on the left to basic on the right
File:Purple Cauliflower Acid Base.jpg|Purple cauliflower soaked in baking soda (left) and vinegar (right). [[Anthocyanin]] acts as an pH indicator.
File:TurmericAcidBase.jpg|[[Turmeric]] dissolved in water is yellow under acidic and reddish brown under alkaline conditions
</gallery>