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  2. Litmus - Wikipedia

    en.wikipedia.org/wiki/Litmus

    Neutral litmus paper is purple. [2] Wet litmus paper can also be used to test for water-soluble gases that affect acidity or basicity; the gas dissolves in the water and the resulting solution colors the litmus paper. For instance, ammonia gas, which is alkaline, turns red litmus paper blue. While all litmus paper acts as pH paper, the opposite ...

  3. pH indicator - Wikipedia

    en.wikipedia.org/wiki/PH_indicator

    Normally, the indicator causes the color of the solution to change depending on the pH. Indicators can also show change in other physical properties; for example, olfactory indicators show change in their odor. The pH value of a neutral solution is 7.0 at 25°C (standard laboratory conditions). Solutions with a pH value below 7.0 are considered ...

  4. Universal indicator - Wikipedia

    en.wikipedia.org/wiki/Universal_indicator

    A roll of universal indicator paper Colors of universal indicator. A universal indicator is a pH indicator made of a solution of several compounds that exhibit various smooth colour changes over a wide range pH values to indicate the acidity or alkalinity of solutions. A universal indicator can be in paper form or present in a form of a ...

  5. Bromothymol blue - Wikipedia

    en.wikipedia.org/wiki/Bromothymol_blue

    Bromothymol blue acts as a weak acid in a solution. It can thus be in protonated or deprotonated form, appearing yellow or blue, respectively. It is bright aquamarine by itself, and greenish-blue in a neutral solution. The deprotonation of the neutral form results in a highly conjugated structure, accounting for the difference in color. An ...

  6. Soil pH - Wikipedia

    en.wikipedia.org/wiki/Soil_pH

    Use of an inexpensive pH testing kit, where in a small sample of soil is mixed with indicator solution which changes colour according to the acidity. Use of litmus paper. A small sample of soil is mixed with distilled water, into which a strip of litmus paper is inserted. If the soil is acidic the paper turns red, if basic, blue.

  7. Litmus test - Wikipedia

    en.wikipedia.org/wiki/Litmus_test

    Litmus test may refer to: Litmus test (chemistry), used to determine the acidity of a chemical solution; Litmus test (politics), a question that seeks to find the character of a potential candidate by measuring a single indicator; The Litmus Test, a Radio 4 programme presented by Fred Harris; The Litmus Test, a 2004 album by Cut Chemist

  8. List of reagent testing color charts - Wikipedia

    en.wikipedia.org/wiki/List_of_reagent_testing...

    It is advised to check the references for photos of reaction results. [1] Reagent testers might show the colour of the desired substance while not showing a different colour for a more dangerous additive. [2]

  9. Congo red - Wikipedia

    en.wikipedia.org/wiki/Congo_red

    Due to a color change from blue to red at pH 3.0–5.2, Congo red can be used as a pH indicator.Since this color change is an approximate inverse of that of litmus, it can be used with litmus paper in a simple parlor trick: add a drop or two of Congo red to both an acid solution and a base solution.