TBS/AFDC 20(4460) P3
ICS 65.160
DRAFT TANZANIA STANDARD
Tobacco and tobacco products-Determination of Nitrogen
TANZANIA BUREAU OF STANDARDS
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TBS/AFDC 20(4460) P3
ICS 65.160
0 FOREWORD
This standard will ensure uniformity in test methodology for assessing the quality of
tobacco and tobacco products.
In the preparation of this Tanzania standard, assistance was drawn from IS 5643:1999
tobacco and tobacco products-methods of test for tobacco.
In reporting the results of a test or analysis made in accordance with this Tanzania
Standard, if the final value observed or calculated is to be rounded off, it shall be done
in accordance with TZS 4.
1 SCOPE
This Tanzania standard specifies a method for the determination of nitrogen from
tobacco and tobacco products
2 REFERENCES
The following referenced standards are indispensable for the application of this draft
standard. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced standard (including any amendments) applies
TZS 4, Rounding off numerical values
3 PRINCIPLE
The sample is heated with sulphuric acid in the presence of a catalyst to oxidize the
sample and convert the nitrogenous matter into ammonium sulphate. Excess of sodium
hydroxide solution is added and liberated ammonia is distilled into standard sulphuric
acid solution. This is followed by titration of the standard sulphuric acid solution with
standard sodium hydroxide solution.
4 APPARATUS
4.1 Kjeldahl Flask, 500 ml capacity.
4.2 Distillation Assembly
The assembly consists of a round-bottom flask of 1000 ml capacity connected to the
condenser by means of a glass tube having ground glass taper joints. The other end of
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TBS/AFDC 20(4460) P3
ICS 65.160
the condenser is extended so as to dip into 50 ml of 0.1 N sulphuric acid contained in
an Erlenmeyer flask of 500 ml capacity to which 3 to 4 drops of methyl red indicator
solution have been added.
5 REAGENTS
5.1 Standard Sulphuric Acid, 0.1 M.
5.2 Standard Sodium Hydroxide Solution, 0.1 M.
4.3 Sodium hydroxide solution
Dissolve 500g of sodium hydroxide free from nitrates and 40 g of sodium thiosulphate
in 1 000 ml of water.
5.4 Concentrate Sulphuric Acid. 0.1 M
5.5 Sodium Thiosulphate Solution
5.6 Potassium Sulphate
5.7 Sodium Sulphate. anhydrous.
5.8 Mercuric Oxide
5.8 Phenolphathalein Indicator
5.10 Methyl Red Indicator
Dissolve 0.4 g of methyl red in 200 ml of ethyl alcohol.
5.11 Salicylic Acid
6 PROCEDURE
6.1 Digestion
Place 0.7 to 3.5 g of sample accurately weighed in a digestion flask and add 30 ml of
sulphuric acid containing one gram of commercial salicylic acid. Shake until thoroughly
mixed and allow to stand, shaking frequently for at least 30 minutes.
Add 5 g of sodium thiosulphate and heat the solution for 5 minutes. Cool, add 10 g of
potassium sulphate or anhydrous sodium sulphate and 0.7 g of mercuric oxide. Heat
very gently keeping the flask in an inclined position until foaming ceases. Increase the
heat till acid boils briskly and digest for a time until the mixture becomes colourless or
nearly so and until oxidation is complete (approximately two hours).
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TBS/AFDC 20(4460) P3
ICS 65.160
6.2 Distillation
After digestion and cooling, dilute with 200 ml of water. Transfer the contents to the
round bottom flask and add a few pieces of granulated zinc or pumice stone to prevent
bumping. Shake, add a few drops of phenolphthalein and shake again. Connect the
receiving Erlenmeyer flask containing 50 ml of 0.1 N sulphuric acid and a few drops of
methyl -red indicator solution. Add gently 50 ml of sodium hydroxide or sodium
thiosulphate solution along the walls of Kjeldahl flask to make the contents thoroughly
alkaline and also to prevent premature loss of ammonia. Heat the flask to boiling and
distil until all the ammonia has passed over into sulphuric acid (first 150 ml of the
distillate generally contains all the ammonia). Titrate this with standard sodium
hydroxide solution.
6.3 Blank determination
Carry out a blank determination using all reagents in the same quantities but without the
material to be tested.
7 CALCULATION
Total nitrogen (on dry basis), 140 (V -v) M
W (100-M)
Where,
V = volume, in ml, of standard Sodium hydroxide solution used to neutralize the acid in
blank determination;
v = volume, in ml, of standard Sodium hydroxide solution used to neutralize the excess
acid in the test with the material;
M= molarity of standard Sodium hydroxide solution;
W = mass in g of the material taken for the test;
and
M = loss on heating percent by mass (see 6.4).
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ICS 65.160
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