Testing Methods: Bergmann & Junk Test for Stability of Nitrocellulose

5.1 Apparatus

For details of B&J bath & reaction tubes assembly refer to IS: 1091-1976, 'Specification for Nitrocellulose'.

5.2 Procedure

The bath is filled with glycerine water mixture (adjusted to boiling to point of 132± 0.2°C ) & the copper tubes with liquid paraffin to the level 50mm below the top of the cover plate when reaction tubes are inserted to a depth of 15cm. The bath is heated and maintained at 132± 0.2°C.

About 10 gm of prepared sample (as given in 1.1) are dried for 4 hrs at 65-70°C in a water oven & cooled in a dessicator over calcium chloride. 2gm each of dried sample are weighted accurately in two portions & transferred into the reaction tubes, brushing down any material adhering to the sides. The samples are compacted gently by pressing to 5cm height. A third reaction tube is set apart as blank. In each of the head –pieces, 15 ml of water is filled & these are fitted to the reaction tubes using 3-in–1 oil at the joints. The reaction tubes are then lowered into the bath with suitable holders. After two hours the tubes are raised up & allowed to cool for about 1 hr. Water in each cup is transferred into a conical flask, then rinsed with 25 ml distilled water & rinsing added to the flask. 20ml of standard 0.1 N hydrochloric acid is added to each reaction tube and to the blank. The tubes are stoppered and shaken vigorously to from uniform slurry. The content of the tubes are transferred to the corresponding flask with the rinsings. To each of the conical flasks 25ml of 0.1 N sodium hydroxide is added and the excess alkali is titrated with 0.1 N HCI using methyl red methylene blue mixed indicator.

mg of Nitrogen/gm of dry Nitrocellulose = (Blank-Titre) x 0.7 x f

where f = factor of 0.1 N HCI