ASTM E258-07 Method Total Nitrogen in Organic Materials by Modified Kjeldahl Method

Scope:

ASTM E258-07 test method covers the determination of total nitrogen in nitrogen-containing organic compounds. Materials containing N-O, N-N linkages are not applicable for this test method.

Test Procedure:
In ASTM E258-07 test method, the sample is digested in a mixture of concentrated sulfuric acid, potassium sulfate, and mercuric oxide. The organic material is oxidized and the nitrogen is converted to ammonium sulfate. Sodium sulfide is added to the digested mixture to precipitate the mercury after which the solution is made strongly alkaline with sodium hydroxide solution. The ammonia which is liberated is distilled into a measured volume of standard acid. The amount of acid neutralized by the ammonia is determined by titrating the excess acid with a standard sodium hydroxide solution.

Specimen size:

0.0001 g of Organic Material (contain 14 to 56 mg of nitrogen)

Data:

Calculate the nitrogen content as follows:

Nitrogen, % = {[(A – B) N × 0.01401]/C} × 100

Where:

A = standard NaOH solution required for titration of the blank, mL,

B = standard NaOH solution required for titration of the sample, mL,

N = normality of the NaOH solution, meq/mL

C = sample used, g, and

0.01401 = meq weight of nitrogen.

mL= millilitre, meq/mL= milliequivalents/millilitre, g = grams, mg = milligram