Here's how it works:
In the traditional Kjeldahl method:
* Digestion: The sample is digested with concentrated sulfuric acid to convert the organic nitrogen into ammonium sulfate.
* Distillation: The ammonium sulfate is then distilled with alkali, liberating ammonia gas.
* Titration: The ammonia gas is absorbed in a standard solution of acid (usually sulfuric or hydrochloric acid). The amount of acid consumed is then used to calculate the amount of nitrogen in the sample.
In the Kjeldahl-Gunning-Jørgensen method:
* Boric acid: Instead of absorbing the ammonia gas in a standard acid solution, it's absorbed in a solution of boric acid.
* Direct Titration: The boric acid solution is then directly titrated with a standard solution of acid (usually hydrochloric acid).
* Advantages: This method is faster and easier to perform compared to the traditional Kjeldahl method, as it eliminates the need for a separate distillation step.
Therefore, the function of boric acid in the Kjeldahl-Gunning-Jørgensen method is:
* To act as a trapping agent for the ammonia gas.
* To create a solution that can be directly titrated with a standard acid solution.
This modification makes the analysis more efficient and convenient.
