ISO 1389-9:1977 pdf download.Phthalic anhydride for industrial use — Methods of test — Part IX: Determination of impurities oxidizable in the cold by potassium permanganate — lodometric method.
This part of ISO 1389 specifies an iodometric method for the determination of impurities oxidizable in the cold by potassium permanganate in phthalic anhydride for industrial use.
This method is not specific for maleic anhydride, for which the polarographic method given in part VII (see the annex) should be used.
ISO 1389-9 should be read in conjunction with part I (see the annex).
2 PRINCIPLE
Oxidation of unsaturated organic acids and anhydrides in a test portion with an excess of cold standard volumetric potassium permanganate solution in the presence of sulphuric acid, followed by iodometric determination of the permanganate remaining.
5 PROCEDURE
Weigh, to the nearest 0,005 g, about 5 g of the test sample, add 100 ml of water and heat gently until the test portion is dissolved. Cool rapidly to room temperature. (Phthalic anhydride is completely soluble under these conditions when hot; a precipitate forms on cooling but this in no way interferes with the rest of the determination.)
After cooling, add 3 ml of the sulphuric acid solution (3.1),
0
cool again to 20 ± 1 C and add 25,0 ml of the potassium permanganate solution (3.3). Mix thoroughly and leave to stand at 20 ± 1 °C for 5 mm. Add 1 g of the potassium iodide (3.2) and titrate the liberated iodine with the sodium thiosulph ate solution (3.4) from the burette (4.1) (the colour change is very sensitive and does not require the addition of starch as indicator, except with coloured solutions).
Carry out a blank test at the same time as the determination, following the same procedure but omitting the test portion.
V0 is the volume, in millilitres, of the sodium
thiosuiphate solution (3.4) used In the blank test;
V1 is the volume, in millilitres, of the sodium
thiosulphate solution (3.4) used in the determination;
m is the mass, in grams, of the test portion.
NOTE — If the concentration of the standard volumetric solutions used Is not exactly as specified in the list of reagents, an appropriate correction should be made.
ISO 1389/I — General.
ISO 1389/Il — Measurement of colour of molten material.
ISO 1389/Ill — Measurement of colour stability.
ISO 1389/tV — Measurement of colour after treatment with sulphuric acid.
ISO 1389/V — Determination of free acidity — Potentiometric method.
ISO 1389/V I — Determination of phthalic anhydride content — Titrimetric method.
ISO 1389/Vil — Determination of maleic anhydride content — Polarographic method.
ISO 1389/VIll — Determination of ash.
ISO 1389/tX — Determination of impurities oxidizable in the cold by potassium permanganate — lodometric method.
ISO 1389/X — Determination of 14-naphthaquinone content — Colorimetric method.
ISO 1389/XI — Determination of iron content — 22’.Bipyridyl photometric method.ISO-1389-9-1977