To determine the presence of carbonates in rocks using acid test.
EQUIPMENTS REQUIRED Diluted HCL (5% to 10%), gloves, cleaning cloth, lab coat, protective glasses.
THEORY
Presence of Carbonate: The presence of carbonate will affect the properties of rock; it will give property to the rock to resist the weathering agents like acid rain, water and others. The presence of carbonate will also increase the strength of rock.
Acid test: This means pouring a drop of dilute (5% or 10 %) hydrochloric acid on a mineral or rock and watching for the bubbles of carbon Dioxide gas to be released. These bubbles signal the presence of carbonate ion in mineral or rock.
The release of bubbles will either be so weak that you will need hand lens to observe or will be so vigorous can be seen with naked eyes. It depends on type and amount of carbonate in particular rock.
PROCEDURE:
- Get the rocks sample for testing.
- Clean off the rock with cloth.
- Carefully pour the HCL acid on rock sample.
- Observe the emission of Carbon Dioxide as fizz and water.
Reaction:
Following Reaction will take place on pouring of HCL on particular rocks:
- Reaction with limestone:
𝐶𝑎𝐶𝑂3+2𝐻𝐶𝐿 = 𝐶𝑂2 + 𝐻2𝑂 + 𝐶𝑎++ + 2𝐶𝐿−−
- Reaction with Dolomite:
𝑀𝑔𝐶𝑂3+2𝐻𝐶𝐿 = 𝐶𝑂2 + 𝐻2𝑂 + 𝑀𝑔++ + 2𝐶𝐿−−
- Reaction with Aragonite:
𝐹𝑒𝐶𝑜3+2𝐻𝐶𝐿 = 𝐶𝑂2 + 𝐻2𝑂 + 𝐹𝑒++ + 2𝐶𝐿—
In All these reaction the emission of and water shows the presence of carbonate in Rock.
A fast emission of can be seen in the case of limestone as it contains maximum amount of, while slow and weak emission in the case of Dolomite.
OBSERVATION:-
| Sample | Acid | Reaction |
RESULTS:
COMMENTS: