BS EN ISO 5399:1998 download free.Leather Determination of water-soluble magnesium salts EDTA titrimetric method.
1 Scope and field of application BS EN ISO 5399 specifies an EDTA titrimetric method for the determination of water-soluble magnesium salts in leather.
It is applicable to all leather which contains magnesium salts.
2 References
ISO 385. Laboratory glassware — Burettes. ISO 4098, Leather — Determination of total water-soluble matter, ivater-solu ble inorganic matter and water-soluble organic matter. ISO 4788, Laboratory glassware — Graduated measuring cylinders.
3 Definition
For the purposes of BS EN ISO 5399, the following definition applies.
magnesium salts content of leather the quantity of magnesium salts, calculated as magnesium sulfate (MgSO4.7H90), obtained by extraction with water under the specified conditions
4 Principle
Aqueous extraction of a test portion, followed by evaporation and drying at 102 ± 2 °C, and sulfating and ashing of the residue at 800 °C, to yield the water-soluble inorganic matter. Treatment of the residue with hydrochloric acid, and titration with standard volumetric disodium ethylenedinitrilotetraacetate solution. (See also 9.4)
5 Reagents
During the analysis, use only reagents of recognized
analytical grade and only distilled water or water of
equivalent purity.
5.1 Ammonium chloride, solid.
5.2 Sodium chloride, solid.
5.3 Ammoniurn hydroxide, 25 % (V/V) solution of
ammonia, Q = 0.880 g/ml.
54 Ammonium hydroxide, 2 molll solution.
5.5 Sodium hydroxide, 2 molll solution.
5.6 Hydrochloric acid, 2 mol/l solution.
5.7 Am mon ia/am moniu,n chloride buffer solution,
of pH 10,5 (see 9.1).
5.8 Disodiu m ethylenedin itriloteiraacetate
dihydrate (Na2EDTA), 0,01 molll standard
volumetric solution (see 9.2).
5.9 Methyl orange, 2 g/l solution.
5.10 Suitable indicator, for example Eriochrome black T (see 9.3).
6 Apparatus
Ordinary laboratory apparatus and
6.1 Burette, with appropriate scale, complying with
the requirements of ISO 385.
6.2 Conical flask, of capacity 300 ml.
6.3 Measuring cylinders, of capacity 50 and 250 ml, complying with the requirements of ISO 4788.
6.4 Thermometer.
7 Procedure
Treat the residue in the crucible after the determination of the water-soluble ash in accordance with ISO 4098. with a little of the hydrochloric acid solution (5.6) dissolved by gentle warming (see 9.4.1). Transfer the solution into the conical flask (6.2). Rinse the crucible several times with a very little of the hydrochloric acid solution and water; neutralize the solution against the methyl orange solution (5.9) with either the ammonia (5.4) or the sodium hydroxide solution (5.5) and boil briefly. Dilute the solution in the flask with 150 ml of water, add 20 ml of the buffer solution (5.7). adjust to 50 °C by cooling or heating, and add the indicator (5.10) until the solution becomes a clear red.
Titrate with the Na2 EDTA solution (5.8) until the colour changes to pure blue (with no red tint).
8 Expression of results
8.1 Calculation
8.1.1 The magnesium salts content, expressed as a percentage by mass as MgO, is given by the formula
V is the volume, in millilitres, of the standard volumetric Na9EDTA solution (5.8) used for the titration;
m is the mass, in grams, of the test portion (see ISO 4098);
0.000 403 is the mass, in grams, of MgO
corresponding to 1,00 ml of exactly 0,01 molIl
Na2 EDTA solution,
and m are as defined in 8.1.1:
0,002 465 is the mass, in grams, of MgSO4.7H90
corresponding to 1.00 ml of
exactly 0,01 molJl Na2EDTA solution.
Take as the result the mean of two determinations, provided that the requirement for repeatability (see 8.2) is satisfied, and express it to one decimal place.
8.2 Repeatability
The results of duplicate determinations carried out by the same operator in the same laboratory shall not differ by more than 0,03 % (rn/rn) MgO or 0,2 % (rn/rn) MgSO4.7H90.
9 Notes on procedure
9.1 Preparation of anunonialammonium chloride buffer solution (5.7)
Add 54 g of the ammomum chloride (5.1) to 350 ml of the ammonium hydroxide solution (5.3) and make up with water to 1 litre.
9.2 Preparation and standardization of the Na2EDTA solution (5.8)
9.2.1 Preparation
Dry the Na2 EDTA at 80°C for several hours. Weigh accurately 3,722 g of the dried Na2EDTA. dissolve in water in a 1000 ml one-mark volumetric flask, make up to the mark and mix well,
The solution can be kept for a practically unlimited time in closed pyrex glass or polythene vessels, but should be restandardized before use.
9.2.2 Standardization
Weigh accurately approximately 0,16 g of chemically pure zinc powder, mix with 100 ml of the hydrochloric acid solution (5.6) and heat on a water-bath until completely dissolved. Transfer the solution to the 250 ml measuring cylinder (6.3). cool and make up to the highest graduation line. Pipette 25 ml of this solution into a conical flask. dilute with 50 ml of water and add 30 ml of the ammonium hydroxide solution (5.4). Add the indicator (5.10) (see 9.3) until clear red. Titrate with the Na9EDTA solution (9.2.1) until the colour is converted to pure blue (without red tint).
9.2.3 Calculation of concen tra lion
The concentration c of the standard volumetric Na9EDTA solution, expressed in moles per litre, is given by the formula
m1 is the mass, in milligrams, of zinc used for the standardization (9.2.2):
V1 is the volume, in millilitres, of the Na9EDTA solution (9.2.1). used for the titration:
0,653 8 is the mass, in milligrams. of zinc corresponding to 1,00 ml of
exactly 0.01 molIl Na2EDTA solution.
9.3 Dilution of the Eriochrome black T indicator
Mix well together 1 part of Eriochrome black T with 300 parts of the solid sodium chloride (5.2). Add the indicator in its solid state to the solution. In this way, the diluted indicator will keep for an unlimited period.
9.4 Preliminary treatment of the test portion If the sulphated ash of water-solubles obtained in accordance with SLC/5, 1966.5.4. is used for the determination, it is necessary first to eliminate any interfering phosphate and/or calcium ions, if qualitative tests have shown their presence. This can be done in accordance with 9.4.1 and 9.4.2.