ANNEXU.K.DETERMINATION OF DICHLOROMETHANE AND 1,1,1-TRICHLOROETHANE

DETERMINATION OF AMMONIAU.K.

6.PROCEDUREU.K.

6.1.Weigh into a 100 ml standard flask a mass (m) of the sample corresponding to 150 mg maximum of ammonia.U.K.

6.2.Add 10 ml of water, 10 ml of methanol (4.1) and 10 ml of barium chloride solution (4.2). Make up to 100 ml with methanol (4.1).U.K.

6.3.Mix and leave overnighs in the refrigerator (5 ^oC).U.K.

6.4.Then filter, or centrifuge the still cold solution in closed tubes for 10 minutes, so as to obtain a clear filtrate or supernatant layer.U.K.

6.5.Pipette 40 ml of this clear solution into the steam distillation apparatus (5.3), followed by 0,5 ml of antifoam liquid (4.5), where appropriate.U.K.

6.6.Distil and collect 200 ml of distillate in a 250 ml beaker containing 10 ml of standard sulphuric acid (4.4) and 0,1 ml of indicator (4.7).U.K.

6.7.Back titrate the excess acid with standard sodium hydroxide solution (4.6).U.K.

6.8.

NB: For potentiometric determination, collect 200 ml of distillate in a 250 ml beaker containing 25 ml of orthoboric acid solution (4.3) and titrate with standard sulphuric acid (4.4), recording the neutralization curve.U.K.