Testing Methods: Nitrogen Content in Nitrocellulose

4.1 Apparatus

There are several methods for the determination of the nitrogen contents, but it is usually done using lunge nitrometer. For details of the apparatus refer to IS 1091- 1976, 'Specification for nitrocellulose'.

4.2 Procedure

About 0.56-0.62 gm of the dried sample (following the procedure given in 1.2) is taken in a tared weighing bottle. The sample is further dried for 4 hrs. in a water oven maintained at 75-80 °C. The weighing bottle with the sample is then cooled in a dessicator over calcium chloride and weighed accurately. The difference gives the mass of the material. 5ml of Analar sulphuric acid (94.5%) is added into the weighing bottle & the mass is made into slurry with a glass rod. The slurry is transferred into the cup of the Nitrometer & drawn into the Nitrometer by operating the stopcock taking care to avoid sucking air into the reaction tube. The weighing bottle & the cup of the Nitrometer are rinsed several times with 94.5% sulphuric acid using a total of 15ml for dissolving and rinsing. The reaction mixture is allowed to stand in Nitrometer arm for 15 minutes & then shaken vigorously for 2 to 3 minutes. The gas generated is allowed to cool to room temperature & the volume is measured under atmospheric pressure by adjusting the leveling tube.

% Nitrogen = [V x P x 0.02246] [(t+273)] x W

V = volume of gas in ml.
P = corrected barometric pressure in mm of mercury.
t = room temperature in °C.
W = weight of the dried material taken.