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March 14, 2006 at 1:07 am #13480
if u know about ds kind of stuff please write back
March 14, 2006 at 1:07 am #472
:if u know about ds kind of stuff please write back
March 14, 2006 at 1:25 am #13481
wats it for like da project ting is it
March 15, 2006 at 2:18 am #13482Anonymous
heres a little information I dug up on the web..hope it helps
Acid – Base Indicators:
The most common method to get an idea about the pH of solution is to use an acid base indicator. An indicator is a large organic molecule that works somewhat like a " color dye". Whereas most dyes do not change color with the amount of acid or base present, there are many molecules, known as acid – base indicators , which do respond to a change in the hydrogen ion concentration. Most of the indicators are themselves weak acids.
The most common indicator is found on "litmus" paper. It is red below pH 4.5 and blue above pH 8.2.
Why do acid-base indicators change colour?
A variety of indicators change color at various pH levels. A properly selected acid-base indicator can be used to visually "indicate" the approximate pH of a sample. An indicator is usually some weak organic acid or base dye that changes colors at definite pH values. The weak acid form (HIn) will have one color and the weak acid negative ion (In-) will have a different color. The weak acid equilibrium is:
HIn –> H+ + In-
What are some natural acid/base indicators?
Flower and leaf pigments often fit this description. For example, take rose petals and crush them with alcohol; you have an acid/base indicator solution. Stew some red cabbage and pour off the juice; you have an acid/base indicator solution.
Many indicators can be extracted from plants; others (like phenolphthalein*) and methyl orange are synthetic. Here are a few 'natural' acid/base indicators. For a longer list of house and garden materials that can be used to make acid-base indicators, see a related question.
* Alizarin is an orange dye present in the root of the madder plant; it was used to dye wool in ancient Egypt, Persia, and India. In an 0.5% alcohol solution, alizarin is yellow at pH 5.5 and red at pH 6.8. Several synthetic modifications of alizarin are also used as acid/base indicators.
* Cochineal is an acid-base indicator made from the bodies of dried female cochineal insects, found in Mexico and Central America. You'll have to grind about 70,000 insects to make one pound of dry indicator. The powder is about 10% carminic acid, which is yellow in acidic solution, and deep violet in alkaline solution. Cochineal solutions are not used much as acid/base indicators these days.
* Curcumin, or tumeric yellow, is a natural dye found in curry powder. It turns from yellow at pH 7.4 to red at pH 8.6.
* Esculin is a fluorescent dye that can be extracted from the leaves and bark of the horse chestnut tree. You'll need to shine a black (ultraviolet) light on the indicator to get the full effect. Esculin changes from colorless at pH 1.5 to fluorescent blue at pH 2.
* Anthocyanin is probably the most readily available acid/base indicator; it is the plant pigment that makes red cabbage purple, cornflowers blue, and poppies red. It changes color from red in acid solution to purplish to green in mildly alkaline solution to yellow in very alkaline solution. The color changes for red cabbage juice are shown to the right.
* Litmus is a blue dye extracted from various species of lichens. Although these lichens grow in many parts of the world, almost all litmus is extracted and packaged in Holland. Litmus is red at pH 4.5 and blue around pH 8.3. While most litmus is used to make litmus papers, some is used as a coloring for beverages.
* Logwood is a dye obtained from the heartwood of a tree that grows in Central America and the West Indies. The extract contains hematoxylin and hematein, which turn bright red in alkaline solution.
information obtained from http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/natural-indicators.shtml some more information is available on everyday household indicators click here
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