ISO 6326-5:1989 pdf download – Natural gas – Determination of sulfur compounds — Part 5 : Lingener combustion method. Barium chloride, standard volumetric solution.
Dissolve 0,38 g of barium chloride dihydrate (BaCI2,2H20) in water n the 1 000 ml one-mark volumetric flask ( and make up to the maik. Staiidardite the solution against 2,00 ml of sulfuric acid solution IdH2SO4) = 0,0025 mol/lJ diluted with about 25 ml of water, by the method detailed in 7.2.3. Calculate the sulfur equivalent of the barium chloride solution in milligrams per millilitre.
1 ml of this standard volumetric solution is equivalent to approximately 0,050 mg of S Coagulant solution.
Dissolve 20 g of magnesium chloride hexahydrate (MgCI706H2O) and 3,5 g of ammonium chloride (NH4CI) in 1 000 ml of water. Adjust to a pH of 8,0 to 8,2 with concentrated ammonium hydroxide (NH4OH) solution. Methanol. Sodium chloride, solution.
Dissolve 100 g of sodium chloride (NaCI) in 1 000 ml of water
7.2.2 Apparatus
Ordinary laboratory apparatus and Photometer, preferably a spectrophotometer having an effective band width of about 50 nrn and equipped wiLh a blue-sensitive photocell for use at 450 nm, or alternatively a filter photometer equipped with a colour filter having a maximum transmission at approximately 450 urn. Absorption cells, with a thickness of 50 mm and a volume of at least 100 ml.
NOTE — The procedure described assumes an absorbonce change of about 0,10 for each 100 pg of sulfur in 50 ml of solution measured in a 50 mm cell. Photometers employing cells of lessor thickncss will not give the precision of measurement stated in this method. One-mark volumetric flask, of capacity 1 000 ml, complying with ISO 1042. One-mark pipettes, of capacities 1 ml, 2 ml, 5 ml,
20 ml and 25 ml, complying with ISO 648. Burette, of capacity 25 ml, graduated in 0.05 ml. complying with 160 305 Beaker, of capacity 250 ml.
7.2.3 Procedure
Add 1 ml of the sodium chloride solution ( to the absorption solution (6.2) in the beaker ( Evaporate on a hotplate until the contents reach a small volume which shall be not less than 1 ml.
WARNING — Do not evaporate over a flame (see 7.1.3.).
Allow the beaker and contents to cool, then add 5 ml ot the coagulant solution ( and ensure that the t;ontents dissolve thoroughly. Add 20 ml of the methanol ( and transfer the contents of the beaker quantitatively to a cell ( Rinse the beaker with three 25 ml portions of methanol (, add the rinsings to the cell and mix thoroughly with a paddle.
NOTE — Tuibidity in the solution at this stage may be caused by the precipitation of magnesium phosphate, and should not interfere with the turbidiiiietik, (ilidlion.
Insert the cell into the photometer ( and record the initial yalvaiiometei reading. Add the barium chloride solution ( in small, equal increments, from the burette ( in the case of sulfur contents below 0,05 mg/rn3, add 0,1 ml at a time; in the case of sulfur curitenis up Lu 0,15 my/m3 add 0,2 ml at a time; in the case of sulfur contents of more than
0,2 mg/m3, add 0,5 ml at a time After each addition, mix the liquid contents of the cell thoroughly with the paddle, then observe and record the galvanometer reading. Add at least five equal increments before the inflection point, and four increments subsequently.
To eliminate, as far as possible, the effect of outside light, it is recommended that the cell be covered after stirring following each addition of solution.
7.2.4 Method of calculation
Plot the volume, in millilitres, of the barium chloride solution ( added ayainst the corresponding galvanometer readings. Join the plotted points. The resulting curve consists of two sections; the intersection point of the tangents to the two branches is the equivalence point.
The total sulfur content in the natural gas is calculated as mass concentration g(S), in milligrams per cubic metre, using the equation.