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.
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).
Sulfate
12.5 mL of the solution used in the test for Chloride, diluted to 15 mL with water, complies with the limit test for sulfates, 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 sulfuric acid. The solution shows not more than a faint turbidity.
Formic acid and oxidisable impurities
Mix 5 mL with 6 mL of sulfuric 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 thiosulfate VS using starch mucilage as indicator. Not less than 0.2 mL of 0.1M sodium thiosulfate 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.
