Acid Test

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What is Acid Test?

An acid test meaning can be given as any qualitative metallurgical or chemical assay that uses acid, historically, and most commonly, the use of a strong acid to recognize gold from the base metals. The acid test is a figuratively definitive test for some attributes - for example, the performance of a product or of the character of a person.


Testing for gold with acid concentrates on the fact that gold is a noble metal, resistant to change by oxidation, corrosion, or acid. The acid test applied for gold is to rub any gold-colored item on a black stone, which will leave a visible mark easily. This mark is tested by applying aqua fortis (which are called as nitric acid), which dissolves the mark of any item other than gold.


Otherwise, if the mark remains, it is tested by applying aqua regia (hydrochloric acid and nitric acid). Else, if the mark is removed, then this test dissolves the gold by proving the item to be genuine gold. For its purity or fineness, more accurate testing of the item can be done through the use of different strengths of aqua regia and the comparative testing of gold items of a known fineness.


Acid Test on How to Spot Minerals Separately

Let us look at the acid test on the process of how to spot minerals separately in brief:


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For some of us, there would have been instances where we had doubted how we would trace the minerals separately from any given substance as it is a part of the Chemistry.

Let us observe how minerals change when we put acid on them.


Apparatus and Ingredients Required to Perform the Test

The equipment and materials given below are required to conduct the acid test to spot the minerals separately:

  • The mineral sample set namely, azurite, lodestone, rose quartz, calcite, amethyst, pyrite, and talc (8 in count).

  • Steel nail.

  • Vinegar (one bottle).

  • Magnifying glass.

  • Paper and Pencil.

  • Paper towel.

  • Eyedropper.

  • Cup (as a Non-reactive metal).

Performing the Experiment

Let us come to know about different steps that are required to be followed to successfully carry out the acid test in spotting the minerals separately. The eight steps given below will guide you to experiment:


Step 1: Make columns under different headings on a piece of paper with words, such as Sample, Powder, and Fizz.


Step 2: To the left side of the paper with the sample heading, write the name of mineral samples such as calcite, pyrite.


Step 3: Pour vinegar of a little amount into the cup provided for you, which you can take with an eyedropper later.


Step 4: Place the mineral sample of your choice on the paper towel and use an eyedropper to pour a vinegar drop (an acid drop) on it.


Step 5: Now, closely look at the mineral and notice the outcome of the chemical reaction, such as, is the vinegar fizzling? If it is, then write “Yes,” under the fizz column, or else, mention “No.”


Step 6: If the vinegar did not give the intended outcome of fizzing, you can use a steel nail and scratch the mineral sample. Also, if there is no impact on the mineral, on the paper, write the mineral being “too hard “under the named powder column. If, in case the scratch produces any mineral powder, add a drop of vinegar to the mineral powder.


Step 7: Using the magnifying glass, observe whether the mineral is fizzing or not, and write the resultant outcome being either yes or no under the column named powder.


Step 8: Finally, follow a similar pattern for any other mineral sample.


Results of the Acid Test

First, let us look at the results of minerals that have calcium carbonate in them. Those minerals will fizz directly in the first attempt. If there are any such minerals with a close bonding at the molecular level having the calcium carbonate as the primary component, they need to be powdered to examine the difference between minerals. This is one of the best and easiest ways where anyone could spot the differences between these minerals.


Acid Test on Testing with Red Cabbage Juice

Procedure

Let us look at one more acid test on testing with red cabbage juice:

  • Add one teaspoon (15 ml) of cabbage juice to two cups each and describe the color of the juice.

  • Keep one cup as a control (do not add anything to it). In another cup, add some liquid drops of acid or liquid base or up to a one-eighth teaspoon of solid acid or solid base.

  • Swirl thoroughly to mix the acid or base and the test solution.

  • Now, observe the color immediately and describe it. (The resultant solutions will be in the red range with an added acid and in the green to the blue range with an added base. The colors in the base are specifically "fragile" and change from one to another hew in a few minutes).

FAQ (Frequently Asked Questions)

1. Where are the Acids and Bases Present in Your Household?

Ans: Give cabbage juice to the students and have the test products from their homes. They should consider a range of things from the bathroom, kitchen, and laundry. What is tested can be limited only by the need to use substances, which are not too highly colored because the colors may interfere with the implementing tests.


An example can be given as soft drinks; lightly or clear colored ones can be tested, but in the case of very dark, probably colas won't give the interpretable colors. Also, by testing a lot of household substances, students could examine whether mixed or ground solids with a small amount of water before testing provide a different result than the solid alone.

2. What can be Used to Test Whether a Substance is Acidic or Basic?

Ans: The strips of pH paper are used to determine pH. A drop of solution is placed on the pH paper strip, and the color developed on the strip is matched with the provided standard color-pH chart to find out the pH value. Although the determination of pH by this process is quick and easy, but not accurate. It gives a fairly accurate value.


Electronic or Digital pH meter is used for accurate measurement of pH. The basic components of an electronic pH meter can be given as a reference (or calomel) electrode, indicator electrode (special glass electrode sensitive to H+), and potentiometer.

3. What is a Litmus Test?

Ans: The acid turns the litmus paper which is in blue into red in colour and there exists no change in the red litmus paper when it seeps into the acid while the base changes litmus paper of red into blue in colour. Also, there will be no effect on the litmus paper of blue color when it seeps into base solution.

4. What is a Litmus Paper Made of?

Ans. The litmus paper is made by dipping a paper in the purple dye solution (litmus) obtained from the crustacean lichen (symbiotic association of fungi and algae).