Nitrogen is a gas widely used in manufacturing, along with a dozen other inert compounds. It is not always advisable to transport or store this gas in its pure form, and sometimes you just need to determine its presence in the substance. For this, the Kjeldahl method is used. The Kjeldahl method consists in the fact that nitrogen, which is contained in the protein-free filtered liquid, is converted into ammonium during the combustion reaction with sulfuric acid. The resulting ammonia is released freely after an alkaline reaction.
Instructions
Step 1
For analysis, take 4 ml of blood, plasma or serum, dilute it with 8 ml of distilled water. Add 8 ml of trichloroacetic acid to the same flask. Stir the solution well and filter.
Step 2
Into the distillation flask, pour 5 ml of the filtered liquid, which by default will contain 1 ml of the analyzed blood. Add 1 ml of reagent No. 2 there, heat the flask on a low flame until white steam appears.
Step 3
Install the flask so that the bottom of it just slightly touches the flames. Consider the combustion process complete when the liquid becomes bluish or colorless.
Step 4
Set the flask aside to cool. Enough one and a half to two minutes. Otherwise, an insoluble precipitate is formed.
Step 5
Pour water down the wall, rinsing the funnel with it. Shake until mixed, warming the flask if necessary.
Step 6
Assemble the device, connect the receiver. Put 10 ml 0.01 N. into the receiver. sulfuric acid solution. Add one or two drops of methylroth. After combining all the ingredients, attach the water jet pump to the receiver.
Step 7
Start passing air through the preparation, pour 33% sodium hydroxide into the distillation part, until the liquid turns from colorless to dark blue or dark brown. This indicates an alkaline reaction.
Step 8
Stop distillation after ten minutes. Close the tap of the water jet pump, open the plug of the receiver, rinse the sulfuric acid from the end of the refrigeration tube. Replace with another receiver with the same 0.01N volume. sulfuric acid solution, do a second distillation.
Step 9
Add caustic soda to the first receiver until a stable yellow color is obtained for 30 seconds.
Step 10
Conclusion: 1 ml 0.01 N. sulfuric acid or sodium hydroxide corresponds to 0.14 mg of nitrogen.
The difference between the amount of sulfuric acid placed in the receiver and the amount of sodium hydroxide taken during titration, produced at 0.14 mg, is equal to the amount of residual nitrogen in the test 1 ml of blood. To show the amount of nitrogen in milligram-percent, the result must be multiplied by 100.
