ISO 13545:2000 pdf download
ISO 13545:2000 pdf download.Lead sulfide concentrates- Determination of lead content – EDTA titration method after acid digestion.
7 Procedure
7.1 Number of determinations
Carry out the determinations at least in duplicate, as far as possible under repeatability conditions, on each test sample.
NOTE Repeatability conditions exist where mutually independent test results are obtained with the same method on identical test material in the same laboratory by the same operator using the same equipment within short intervals of time.
7.2 Blank test
Carry out a blank test in parallel with the analysis using the same quantities of all reagents but omitting the test portion.
7.3 Decomposition of test portion
Transfer the test portion to a 400 ml conical beaker and moisten with 5 ml of water. Add 10 ml to 20 ml of nitric acid (4.2) and 1 ml to 2 ml of bromine (4.14) in small portions, cover with a watch glass and heat gradually to decompose the test portion completely. Cool slightly, rinse the underside of the watch glass and the inside of the conical beaker with a minimum volume of warm water. Add 10 ml of dilute sulfuric acid (4.8) and heat until strong white fumes are evolved, then cool.
If the residue appears dark (presence of carbon), slowly add a small amount of the nitration mixture (4.11) to the hot solution until the solution is colourless or bluish and heat until strong white fumes are evolved, then cool.
Carefully add 5 ml of water and 10 ml of hydrobromic acid (4.7), heat gradually until strong white fumes are evolved then cool. Add 5 ml of dilute sulfuric acid (4.8) and 10 ml of hydrobromic acid (4.7), again heat gradually until strong white fumes are evolved then cool.
NOTE The above step is not required if the sample contains less than 0,5 % (rn/rn) of arsenic, tin, antimony and/or selenium.
7.4 Formation of lead sulfate
Carefully rinse the wall of the conical beaker with water and adjust the volume to about 100 ml with water. Heat gradually until boiling to dissolve the salts and cool to room temperature. Add 10 ml of ethanol or methanol (4.21), allow the lead sulfate precipitate to settle for at least 2 h.
NOTE It is preferable to allow the lead to settle overnight using the method described in NOTE 1 under 7.5.
7.5 Separation and dissolution of lead sulfate
Filter the precipitate through a fine porosity filter paper and wash the inside of the beaker two or three times with dilute sulfuric acid washing solution (4.10). Wash the precipitate on the filter paper three or four times with dilute sulfuric acid washing solution (4.10), then with a small amount of water. Reserve the filtrate and washing in a beaker (400 ml) for determination of lead by AAS (as described in 7.7). Rinse the precipitate into the original 400 ml conical beaker with warm water.
NOTE 1 Instead of using the above steps, the following method is available:
Initial decanting of liquid through a fine porosity filter paper leaving precipitate in the beaker. Washing the precipitate three or four times with dilute sulfuric acid washing solution (4.10) in the beaker by decantation, then with water. Washing the precipitate on the filter paper three or four times with dilute sulfuric acid washing solution (4.10) then with water. Reserving the filtrate and washing in a beaker (400 ml) for determination of lead by AAS (as described in 7.7).
Place the original conical beaker containing the main precipitate under the original funnel. Add 30 ml of warm ammonium acetate solution (4.19) to the filter paper in order to dissolve the lead sulfate on the filter paper, then wash with hot water. Collect the washing in the original conical beaker. Wash around the inside of the beaker with small amounts of hot ammonium acetate solution (4.19). Heat to boil for a few minutes to dissolve the lead sulfate.Filter the solution through the original flter paper, wash well with warm ammonium acetate washing solution (4.20).Collect the filtrate and washing in a 400 ml conical beaker, dilute to about 150 ml with water and cool.
NOTE 2 If the solution contains a small amount of Fell ion, the end point of titration is not clear. In such a case, about 0,2 gof L(+) – ascorbic acid (4.22) should be added to the solution prior to titration to cause reduction of Fe(Il) to Fe(II).
