TP Nº 11

Resumen textual Farmacopea Británica y Europea  2007 para el examen del ácido acético diluido 6 %

"Dilute Acetic Acid
 
 DEFINITION
 
 Acetic Acid (6 per cent) contains not less than 5.7% and not more than 6.3% w/w of  acetic acid, C2H4O2. It may be prepared by mixing 182 g of Acetic Acid (33 per  cent) with 818 g of Purified Water.
 
 IDENTIFICATION
 
  A. Strongly acidic.
 
  B. When neutralised, yields the reactions characteristic of acetates, Appendix VI.
 
 TESTS
 
 Weight per ml
 
 About 1.005 g, Appendix V G.
 
 Heavy metals
 
 Evaporate 20.0 ml to dryness and add 20 ml of water . 12 ml of the resulting solution  complies with limit test A for heavy metals, Appendix VII. Use lead standard  solution (1 ppm Pb) to prepare the standard (1 ppm).
 
 Chloride
 
 Dilute 5.0 ml with sufficient water  to produce 100 ml. 15 ml of the resulting solution  complies with the limit test for chlorides, Appendix VII (70 ppm).
 
 Sulphate
 
 12.5 ml of the solution used in the test for Chloride, diluted to 15 ml with water ,  complies with the limit test for sulphates, Appendix VII (240 ppm).
 
 Aldehydes
 
 Distil 75 ml. To the first 5 ml of the distillate add 10 ml of a 5% w/v solution of  mercury(II) chloride, make alkaline with 5M sodium hydroxide, allow to stand for 5  minutes and acidify with 1M sulphuric acid. The solution shows not more than a faint  turbidity.
 
 Formic acid and oxidisable impurities
 
 Mix 5 ml with 6 ml of sulphuric acid and cool to 20°. Add 0.4 ml of 0.0167M  potassium dichromate VS, allow to stand for 1 minute, add 25 ml of water  and 1 ml  of freshly prepared dilute potassium iodide solution and titrate the liberated iodine  with 0.1M sodium thiosulphate VS using starch mucilage as indicator. Not less than  0.2 ml of 0.1M sodium thiosulphate VS is required.
 
 Readily oxidisable impurities
 
 To 25 ml add 0.2 ml of 0.02M potassium permanganate VS and allow to stand for 1  minute. The pink colour is not entirely discharged.
 
 Non-volatile matter
 
 When evaporated to dryness and dried at 105°, leaves not more than 0.01% w/w of  residue.
 
 ASSAY
 
 Add 30 ml of water  to 20 g in a stopper flask and titrate with 1M sodium hydroxide  VS using phenolphthalein solution R1 as indicator. Each ml of 1M sodium hydroxide  VS is equivalent to 60.05 mg of C2H4O2. "