ISO 20978:2020

ISO 20978:2020 pdf download.Liming material – Determination of neutralizing value – Titrimetric
methods.
5 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade.
NOTE Commercially available solutions can be used.
5.1 Water, according to ISO 3696, grade 3.
5.2 Hydrochloric acid standard solution, c(HC1) = 0,5 mol/l.
This solution can be purchased from a chemical supply company certified to have a concentration within a 0,4 % variance (0,498 M to 0,502 M).
If preparing from concentrated HC1, determine the exact concentration of the solution by titration with sodium hydroxide standard solution (i3) using phenolphthalein solution (5A) as indicator.
Apply the appropriate correction factor in the calculation of the results (see Clause 9).
In case of any doubt about the concentration of the HC1 solution, measuring the neutralizing value of a precipitated calcium carbonate (PCC, 5&) is recommended.
5.3 Sodium hydroxide standard solution, c(NaOH) = 0,25 mol/l.
This solution can be purchased from a chemical supply company certified to have a concentration within a 0,2 % variance (0,249 5 M to 0,250 5 M).
If preparing from NaOH pellets, determine the exact concentration of the standard solution by titration against approximately 2 g of dried potassium hydrogen phthalate (KHC8H4O4), weighed to the nearest 0,00 1 g.
The solution shall be stored in a polyethylene bottle and absorption of carbon dioxide during storage should be avoided.
NOTE 1 ml of 0,25 mol/l sodium hydroxide solution is equivalent to 51,055 mg of potassium hydrogen phthalate.
Apply the appropriate correction factor in the calculation of the results (see Clause 9).
In case of any doubt about the concentration of the NaOH solution, measuring the neutralizing value of a precipitated calcium carbonate (PCC, 5) is recommended.
5.4 Phenolphthalein indicator solution.
Dissolve 0,25 g of phenolphthalein in 150 ml of ethanol with a mass fraction of 93 % and dilute with water to 250 ml.
The phenolphthalein solution (SA) is a colour indicator to determine when the end point pH is reached and is only suitable in Method A with an end point pH of 7. The indicator is not required if a pH electrode is used to monitor end point pH.
NOTE If there is a buffering capacity in the sample, a deviation can occur between phenolphthalein indicator solution (changes at pH 8,3) and pH end point with pH meter (7,0).
5.5 Hydrogen peroxide solution.
Dilute one volume of hydrogen peroxide [p (H2O2) = 30 g/100 ml] with four volumes of water.
Hydrogen peroxide is used in Method B to oxidize any reduced iron in slag liming materials.
5.6 Precipitated calcium carbonate.
Precipitated calcium carbonate of recognized analytical grade, minimum 99 % CaCO3.
Quality control check by using precipitated calcium carbonate and blank solution should be used in
each series of measurements.
6 Apparatus
Usual laboratory apparatus and, in particular, the following.
6.1 Test sieve, conforming to the requirements of ISO 3310-1, of maximum aperture size 250 ╬╝um.
6.2 pH meter, minimum sensitivity 0,05 pH units, with a suitable glass electrode and a calomel or
other reference electrode or a combined electrode, calibrated using two buffer solutions whose pH
values cover the range pH 4 to pH 7.
A pH meter is not required if using phenolphthalein to determine end point pH of 7 in Method A.
6.3 Mechanical stirrer, e.g. magnetic stirrer.
6.4 Desiccator.
7 Sampling
Sampling is not part of the method specified in this document. Recommended sampling methods are
described in ISO 14820-1 and ISO 14820-3 . Prepare the sample of the liming materials in accordance with ISO 14820-2.ISO 20978 pdf download.

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