BS ISO 4323:2018 pdf free.Soaps — Determination of chloride content — Potentiometric method.
This document specifies a potentiometric method for the determination of the chloride content of soaps, containing or not containing other surface active agents, and also of compounded products.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 385, Laboratory glassware — Burettes
ISO 8212, Soaps and detergents — Techniques of sampling during manufacture
4 Principle
Potentiometric titration of the chloride (Cl-) ions with standard silver nitrate solution in an acidic medium, by using either a silver ion selective electrode plus a reference electrode or a combined electrode.
5 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity.
5.1 Nitric acid, approximately 6 mol/l solution.
5.2 Silver nitrate. approximately 0,1 mol/l solution.
Dissolve 8,5 g of silver nitrate in water in a 500 ml one-mark volumetric flask, dilute to the mark and iriix. Store this solution capped in a dark amber-coloured flask. Standardize the solution before use (8.2).
8.2 Calibration of the silver nitrate solution
8.2.1 Titration
Take 5,00 ml and 10,00 in! respectively the appropriate standard reference sodium chloride solution (5.4 or 5.5) and place in two clean, dry vessels of convenient capacity (for example 150 ml). Carry out the following titration on the contents of each vessel.
After acidification by the nitric acid solution (&1) add sufficient water to bring the total volume to about 100 ml.
Maintain the sample at a lower pH can avoid the silver ion interact with OH- to form Silver Oxide (Ag20) precipitation, minimize other anionic ions (such as fatty acid) interference with the AgCI formation, and improve the binding between the titrant and the analyte.
Stir the resultant solution and immerse the combined electrode or the silver ion selective electrode and a reference electrode (6.2), connect the electrode to the potentiometer (fd) and, after having verified the zero of the apparatus, note the value of the starting potential.
Add, from the burette (6,4), in 1 ml portions, the silver nitrate solution (5.2 or 5.3) having the same normality as that of the standard reference sodium chloride solution (SA or 55) used. After each addition, await the stabilization of the potential.
8.3.2 Titration
Titrate with the silver nitrate solution (5.2 or 5.3) corresponding to the expected chloride content and note the end-point of the reaction in accordance with the instructions given in 8.2. Calculate the VEQ in accordance with the formula in 8.2.1.
lithe experiment is done by an autotitrator, the instrument vill automatically display the VEQ value after the end point is reached.
8.3.3 Blank test
Carry out a blank test with 50 ml of water, 50 ml of isopropanol (5.6) and 5 ml of nitric acid solution (SJJ, which is the same composition as that for the test portion described in 8.3.1.BS ISO 4323:2018 pdf free download.