Micro-chemical test for hydrogen carbonate (bicarbonate): Difference between revisions
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'''Micro-chemical test for hydrogen carbonate (HCO<sub>3</sub><sup>-</sup>)''' | |||
More information about the necessary equipment and materials see Article Micro-chemistry. | More information about the necessary equipment and materials see Article Micro-chemistry. | ||
== preliminary remark about the micro-chemical differentiation of carbonates and hydrogen carbonates == | |||
The micro-chemical differentiation of carbonates and hydrogen carbonates in practice is difficult. Therefore it is normally necessary to verify the obtained results by analyzing the salt samples with other methods such as polarized light microscopy or other analytical methods. | |||
== Procedure == | == Procedure == | ||
===pH value of hydrogen carbonate salts === | ===pH value of hydrogen carbonate salts === | ||
An aqueous solution of alkali hydrogen carbonates has a pH of around 8. | |||
For mixed salts of alkali carbonates and hydrogen carbonates (e.g., Trona (Na<sub>3</sub>H(CO<sub>3</sub>)<sub>2</sub>.2H<sub>2</sub>O) the pH is around 10. | |||
===Hydrogen carbonate test using mineral acids === | ===Hydrogen carbonate test using mineral acids === | ||
When adding diluted hydrochloric or nitric acid to the crystalline salt or | When adding diluted hydrochloric or nitric acid (2M) to the crystalline salt or its solution, CO<sub>2</sub> is released and can be observed as bubbling. | ||
=== | ===Differentiation between hydrogen carbonate and carbonate using calcium chloride solution === | ||
Adding a drop of | Adding a drop of CaCl<sub>2</sub> solution (1% aqueous solution) to a sample solution containing only HCO<sub>3</sub><sup>-</sup> but no CO<sub>3</sub><sup>2-</sup> leads to no visible reaction. | ||
Revision as of 13:22, 1 June 2012
Author: Christine Bläuer
back to Micro-chemical testing
Micro-chemical test for hydrogen carbonate (HCO3-)
More information about the necessary equipment and materials see Article Micro-chemistry.
preliminary remark about the micro-chemical differentiation of carbonates and hydrogen carbonates
The micro-chemical differentiation of carbonates and hydrogen carbonates in practice is difficult. Therefore it is normally necessary to verify the obtained results by analyzing the salt samples with other methods such as polarized light microscopy or other analytical methods.
Procedure
pH value of hydrogen carbonate salts
An aqueous solution of alkali hydrogen carbonates has a pH of around 8.
For mixed salts of alkali carbonates and hydrogen carbonates (e.g., Trona (Na3H(CO3)2.2H2O) the pH is around 10.
Hydrogen carbonate test using mineral acids
When adding diluted hydrochloric or nitric acid (2M) to the crystalline salt or its solution, CO2 is released and can be observed as bubbling.
Differentiation between hydrogen carbonate and carbonate using calcium chloride solution
Adding a drop of CaCl2 solution (1% aqueous solution) to a sample solution containing only HCO3- but no CO32- leads to no visible reaction.
Literature
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