ISO 5790-1979 pdf free.Inorganic chemical products for industrial use — Generalmethod for determination of chloride content — Mercurimetric method.
1.This lnternational Standard specifies a general mercurimetricmethod for the determination of chloride content.
2Field of application:The method is applicable to inorganic chemical products forindustrial use. It enables quantities of chloride(Cl-) exceeding1 mg in the test portion to be determined with an absolute errorof 0,2 to 0,5 mg, according to the concentration of the standard volumetric solution used.
The determination is not affected by the elements or com-pounds listed in annex A when they are present in quantities upto the specified limits.
ln certain cases, this annex contains instructions for the treat-ment to be applied to reduce or eliminate interferences.
3.Principle:Conversion ofCl- ions into weaklyionized mercury(l)chloride,using highly ionized standard volumehric mercuryill)nitrate solution. Detection of the endpoint by reaction of theexcess of mercury(ll) nitrate with 1,5 diphenylcarbazone usedas an indicator, by the appearance of a violet colour.
4.Reagents:During the analysis, use only reagents of recognized analyticalgrade and only distilled water or water of equivalent purity.
Prepare this solution at the time of use. Do not use the solutionfor more than 30 min after preparation.
Place the same volume of water as in the test solution (6.2.1) ina 500 ml conical flask,add 3 drops of the bromophenol bluesolution (4.11) and the nitric acid solution (4.2), drop by drop,until the colour changes from blue to yellow.Add an excess of3 drops of this acid,0.5 to 1,0 ml of the diphenylcarbazonesolution (4.12)and,from the burette (5.1)，the minimumvolume of the standard volumetric mercury(ll) nitrate solution(4.8,4.9 or 4.10) necessary to change the colour of the solutionfrom yellow to mauve.Place 40,0 ml of the standard reference sodium chloridesolution (4.4),160 ml of water and 3 drops of the bromophenolblue solution (4.11) in a 500 ml conical flask.Add the nitric acidsolution (4.2)，drop by drop,until the colour of the indicatorchanges from blue to yellow and then add an excess of 3 dropsof this acid and the volume of the diphenylcarbazone solution(4.12) added for the standard end-point matching solution(4.7).Titrate (see note in 6.2.2)with the mercury(Il) nitratesolution (4.8.1) to be standardized until the colour matches themauve of the standard end-point matching solution and deductthe volume of the mercury(llnitrate solution (4.8.1) addedduring the preparation of this standard end-point matchingsolution (generally 1 drop).ISO 5790 pdf download.