In the following test for Sulfated Ash, ammonium carbonate solution was added. What is the purpose of adding ammonium carbonate solution?

Heat a silica crucible to redness for 30 minutes, allow to cool in a desiccator and weigh. Place 1g of the substance in the crucible and add 2ml of 1mol/L Sulphuric Acid. Heat, first on a water bath, then cautiously over a flame,then progressively to about 600°C. Continue the incineration until all black particles have disappeared and then allow the crucible to cool. Add a few drops of 1mol/L Sulphuric Acid, heat and incinerate as before and allow to cool. Add a few drops of Ammonium Carbonate solution (15.8g in 100ml).Evaporate and incinerate carefully,allow to cool, weigh and repeat the ignition for 15 minutes to constant weight.

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What is the use of Ammonium Carbonate solution in this test.

The purpose of adding ammonium carbonate solution in this test for Sulfated Ash is to convert any remaining sulfates into sulfates of ammonium. This step ensures that all the sulfated ash present in the substance being tested is converted to sulfates of ammonium, which can then be accurately measured. This step helps in determining the amount of ash residue left after incineration.

The purpose of adding ammonium carbonate solution in the Sulfated Ash test is to convert any remaining sulphuric acid to ammonium sulfate, which is volatile and can be easily driven off during the subsequent incineration step.

To understand why it is necessary to add ammonium carbonate solution, let's break down the steps of the test:

1. Heat a silica crucible to redness for 30 minutes, allow to cool in a desiccator and weigh: This step ensures that the crucible is thoroughly clean and dry before starting the test.

2. Place 1g of the substance in the crucible and add 2ml of 1mol/L Sulphuric Acid: This step is the initial treatment of the sample with sulfuric acid, which helps in the decomposition of organic material and certain inorganic compounds.

3. Heat, first on a water bath, then cautiously over a flame, then progressively to about 600°C: This step involves gradually heating the sample to a high temperature, which causes the combustion of organic matter and the oxidation of certain inorganic compounds.

4. Continue the incineration until all black particles have disappeared and then allow the crucible to cool: This step ensures complete combustion of organic matter and removal of any remaining impurities.

5. Add a few drops of 1mol/L Sulphuric Acid, heat, and incinerate as before and allow to cool: This step is repeated to ensure complete removal of any remaining organic residue.

Now, at this point, there might still be some residual sulfuric acid remaining in the crucible. If we directly proceed to the next step (i.e., evaporation and incineration), the remaining sulfuric acid can react with the sample, leading to inaccurate results.

6. Add a few drops of Ammonium Carbonate solution (15.8g in 100ml): By adding ammonium carbonate solution, we neutralize any remaining sulfuric acid. The reaction that takes place is:

H2SO4 + (NH4)2CO3 → (NH4)2SO4 + H2O + CO2

As a result, ammonium sulfate, water, and carbon dioxide are formed. Ammonium sulfate is volatile, and it can be easily removed during the subsequent heating steps.

7. Evaporate and incinerate carefully, allow to cool, weigh, and repeat the ignition for 15 minutes to constant weight: The addition of ammonium carbonate allows for accurate determination of the sulfated ash content by ensuring that all organic residues and sulfuric acid are removed.

So, the purpose of adding ammonium carbonate solution in the Sulfated Ash test is to remove any remaining sulfuric acid by converting it to volatile ammonium sulfate, which can be easily expelled during the subsequent heating steps.