BS 5705-5:1981 pdf free download.British Standard Methods of test for Sodium hexafluorosilicate for industrial use.
1 SCOPE AND FIELD OF APPLICATION
BS 5705-5 specifies a gravimetric method for the determination of the free silica content of sodium hexefluorosilicate for industrial use.
The method is applicable to products having free silica contents, expressed as Si02, equal to or greater than 0,05% (rn/rn).
2 REFERENCE
ISO 5444, Sodium hexafluoro silicate for industrial use — Determination of loss in mass at 105 °C.
3 PRINCIPLE
Extraction from a test portion of compounds soluble in acetic acid solution and weighing of the residue after heating at 600 °C. Removal from the residue, of silica by evaporation with hydrofluoric acid solution and of reSidual fluorides by heating with ammonia solution, and reweighing of the residue after heating at 600 °C.
4 REAGENTS
During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity.
4.1 Hydrofluoric acid, p approximately 1,14 g/ml. about
40 % (rn/rn) solution.
4.2 Acetic acid, glacial, p approximately 1,05 9/mI.
4.3 Ammonia solution, p approximately 0,88 g/mI, about
34 % (rn/rn) solution.
5 APPARATUS
Ordinary laboratory apparatus and
5.1 Platinum crucible, capacity 35 to 50 ml.
5.2 Electric furnace, capable of being controlled at
600± 10°C.
6 SAMPLING1
Use the residue from the determination of loss in mass
at 105 °C (see ISO 5444) to prepare the test sample.
7 PROCEDURE
7.1 Test portion
Weigh, to the nearest 0,000 1 g, about 1 g of the test sample, finely ground and previously dried at 105 °C (see clause 6).
7.2 Determination
Quantitatively transfer the test portion (7.1) to a 400 ml beaker and add 5 ml of the acetic acid (4.2) and 200 ml of water. Bring the contents of the beaker to the boil and boil gently for 10 mm with continuous stirring. Allow to stand, maintaining the temperature for 10 mm. Filter first the decanted supernatant liquid and then the suspended residue, ensuring that the residue is transferred quantitatively on to the filter paper used for this purpose. Wash the residue four or five times with the hot water that was used to rinse the beaker. Transfer the filter paper and residue to the clean, dry platinum crucible (5.1), previously weighed to the nearest 0,000 1 g. Heat the crucible and contents for 45 mm in the furnace (5.2). controlled at 600 ± 10 °C, transfer to a desiccator, allow to cool, and weigh to the nearest 0,000 1 g. Repeat the operations of heating (for 30 mm), cooling and weighing until the difference between two successive weighings does not exceed 0000 2 g.
Then add 2 ml of the hydrofluoric acid solution (4.1) to the crucible (5.1) and carefully evaporate the contents of the crucible to dryness in a fume cupboard. Allow to cool, add a small filter paper of known ash to the crucible, moisten it with 2 drops of the ammonia solution (4.3) and heat gently to dryness. Heat the crucible and contents for 45 mm in the furnace (5.2), controlled at 600 ± 10 °C. transfer to a desiccator, allow to cool, and weigh to the nearest 0,000 1 g. Repeat the operations of heating (for 30 mm), cooling and weighing until the difference between two successive weighings does not exceed 0,000 2 g.
8 EXPRESSION OF RESULTS
The free silica content, expressed as a percentage by mass of Si02, is given by the formula
m0 is the mass, in grams, of the test portion (7.1);
is the mass, in grams of the residue before heating with hydrofluoric.acid;
m2 is the mass, in grams, of the residue after heating with hydrofluoric acid;
m3 is the mass, in grams, of the filter paper ash.
9 TEST REPORT
The test report shall include the following particulars a) an identification of the sample;
b) the reference of the method used;
c) the results and the method of expression used;
d) any unusual features noted during the determination;
e) any operation not Included in BS 5705-5 or in the International Standard to which reference is made, or regarded as optional.