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1、INTERNATIONAL STANDARD 787/X1X INTERNATIONAL ORGANIZATION FOR STANDARDIZATION .MEXLWHAPOflHAR OPrAHH3AUMR IlO CTAHAAPTA3AUCIH.ORGANlSATlON NTERNATIONALE DE NORMALISATION General methods of test for pigments - Part XIX Me thodes g take care to avoid losses by splashing. Cool and add sodium hydroxide
2、solution (4.6) until just alkaline. Cool again and adjust the pH to 8.0 -f 0.5 measured by the pH meter Filter through filter paper and wash with hot water, collecting the filtrate and washings in a 250 ml one-mark volumetric flask Cool, make up the mark and mix 8.2 Pipette 10 ml of this solution to
3、 a 100 ml glass beaker. NOTE - If the nitrate content is found to be greater than 0.1 %, carry out a second determination, using 5 ml of solution. 8.3 Add to the beaker 1 ml of sodium salicylate solution (4.4) and proceed as specified in clause 7, including the determination of the absorbance at 410
4、 nm. 8.4 From the known absorbance of the test solution, determine from the calibration graph the corresponding mass of nitrate in milligrams. 9 EXPRESSION OF RESULTS Calculate the water-soluble nitrate content expressed as N03, as a percentage by mass, by the formula : 25a 2% where a is the mass, i
5、n milligrams, of NOa corresponding to the absorbance of the test solution; m is the mass, in grams, of the pigment from which the clear aqueous extract was obtained. NOTE - If 5 ml of the extract was taken because the nitrate 25a content was greater than 0,l %, the formula becomes - In IO TEST REPOR
6、T The test report shall include the following particulars a) a reference to this International Standard or to a corresponding national standard, b) type and identification of the product under test; c) any deviation, agreed or otherwise, from the test procedure specified; d) the result of the test,
7、and whether the hot or cold extraction method was used; e) date of the test. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 08:06:45 MDTNo reproduction or networking permitted without license from IHS -,-,-