1、Aluminium and aluminium alloys - Determination of nickel - Spectrophotometric method using dimethylglyoxime Aluminium et alliages daluminium - Dosage du nickel - Methode spectrophotometrique d la dim then add an excess of about 0.5 ml of bromine water solution (4.12). Allow to cool, and add slowly,
2、while stirring, the ammonia solution (4.4) until the colour disappears (about 2,5 to 2.8 ml) and then add an excess of 1 ml. Cool the solution to ambient temperature, add 1 ml of the dimethylglyoxime solution (4.19). make up to volume and mix. 7.3.5 Photometric measurements Measure the absorbance of
3、 each solution after 10 min, without however exceeding 30 min, using the spectro- photometer (5.2) at the maximum of the absorption curve (wavelength about 445 nm), after having adjusted the apparatus to zero absorbance against the compensating solution. 7.3.6 Plotting of the.curve Plot a graph, sho
4、wing, for example, on the abscissa the values, expressed in milligrams, of the quantities of nickel contained in 100 ml of the reference solution and on the ordinate the corresponding absorbance values. 7.4 Determination 7.4.1 Preparation of the test solution Place the test portion (7.1) in a beaker
5、 of suitable size (400 ml for example) and cover with a watch glass. Add, in small portions, cooling if necessary, 25 ml of the hydro- chloric acid solution (4.7). Wait until the reaction subsides and heat gently to complete the dissolution; add a small quantity (from a few drops to a few millilitre
6、s) of the hydrogen peroxide solution (4.13) and then heat to elim- inate the excess of hydrogen peroxide and to complete, if need be, the dissolution of the test portion. Rinse the walls of the beaker and therwatch glass with hot water, collecting the washings in the same beaker, dilute to about 80
7、ml with hot water and filter through a close textured filter. Wash the filter and the residue with hot water and collect the filtrate and the washings in a beaker of suitable size (400 ml for example). Keep this solution. Transfer the filter with the residue to a platinum crucible, dry and then heat
8、 carefully until combustion of the filter (the temperature should not exceed about 600 “C). After cooling, transfer to the crucible 1 to 2 ml of the sulphuric acid solution (4.6), 5 ml of the hydrofluoric acid solution (4.3) and finally, drop by drop, the nitric acid solution (4.2) until a clear sol
9、ution is obtained. Evaporate this solution until the white sulphuric acid fumes have been completely eliminated and then heat for about 10 min (the temperature should not exceed about 700 “C). Allow to cool, then take up with a few millilitres of hot water and 1 to 2 ml of the hydrochloric acid solu
10、tion (4.7). Heat gently, add the solution obtained to the test solution and adjust the volume to about 150 ml. Add 0,5 ml of the iron(lll) chloride solution (4.16) and 45 ml of the sodium hydroxide solution (4.15). Cover the beaker with a watch glass, heat the solution to 70 to 90 C and keep the sol
11、ution at this temperature for 20 min without boiling; finally, boil the solution for 2 to 3 min. Filter the residue through a sintered glass crucible of suitable porosity (from 15 to 40 ,um for example) and wash immediately, with hot sodium hydroxide solution (4.15), the residue and the beaker so as
12、 to collect in the crucible any residue which may adhere to the walls of the beaker. Dissolve the residue on the crucible with 10 ml of the hot acid mixture (4.11) diluted at the moment of use with IO ml of hot water, wash carefully with hot water and collect the filtrate and the washings in the bea
13、ker used for the attack of the test portion. Heat to complete the disso- lution of the salts, cool to ambient temperature and transfer the solution quantitatively to a 200 ml or 500 ml volumetric flask, according to the expected nickel content. Make up to volume and mix. 7.4.2 Taking of the aliquot
14、According to the expected nickel content, for the volume of the test solution (7.4.1), the volume of the aliquot of the test solution to be taken and the possible dilution, the taking of the aliquot for the colour reaction, follow the indications given in table 2 . To a beaker of suitable capacity (
15、150 ml for example), transfer the aliquot of the test solution and bring thevolume to about 40 ml by concentration or dilution. Add 10 ml of tartaric acid solution (4.10) and 5 ml of the hydroxyl- ammonium chloride solution (4.17). Add, while stirring and checking with the aid of the pH meter (5.1),
16、 the quantity of the sodium hydroxide solution (4.14) necessary to bring the value of the pH to about 4,5 to 5. Finally add 10 ml of the sodium thiosulphate solution (4.18) and, while stirring, adjust the value of the pH to 6,5 using first the sodium hydroxide solution (4.14) and then the sodium hyd
17、roxide solution (4.15). Remove from the solution the electrodes (or the combined glass electrode), wash with as little water as possible and add the washings to the solution. Transfer the solution quantitatively to a separating funnel of suitable capacity (250 ml for example), washing with as little
18、 water as possible. Continue according to the procedure described in 7.3.2 to 7.3.4. 1) The addition of iron(lll) chloride solution is not necessary if the iron content of the alloy is over about 0,2 %. 4 Copyright International Organization for Standardization Provided by IHS under license with ISO
19、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 3979-1977 (E) TABLE 2 Expected nickel content % Mm) from 0,001 to 0,07 from 0.07 to 0,15 from 0,15 to 0.4 from 0,4 to 1 from 1 to 2 from 2 to 3 Volume of the Aliquot of the test solution (A) test solution (A) (7.4
20、1) to be taken ml ml 200 100.0 200 50.0 200 20.0 500 20,o 500 50,o 500 50.0 Volume of the dilution of the aliquot taken (BI ml - - - 250.0 250.0 Volume of the aliquot of solution A or B, taken for the colour reaction ml 100.0 (A) 50.0 (A) 20.0 (A) 20,O (A) 50.0 (B) 25,0 (B) Mass of nickel present i
21、n the coloured solution IN from 5 to 350 from 175 to 375 from 150 to 400 from 160 to 400 from 200 to 400 from 200 to 300 7.4.3 Photometric measurements Carry out the photometric measurements on the test solution and the blank test solution after 10 min, without however exceeding 30 min, according to
22、 the procedure described in 7.3.5, having adjusted the apparatus to zero absorbance against water. 8 EXPRESSION OF RESULTS By means of the calibration curve (see 7.3.6), determine the quantity of nickel corresponding to the values of the photometric measurements. The nickel (Ni) content is given, as
23、 a percentage by mass, by the formula (m, -m,) XD 10 xm, where m, is the mass, in grams, of the test portion; m, is the mass, in milligrams, of nickel found in the aliquot of the test solution; m2 is the mass, in milligrams, of nickel found in the corresponding aliquot of the blank test solution; D
24、is the ratio of the volume of the test solution to the volume of the aliquot taken for the colour reaction. 9 TEST REPORT The test report shall include the following information : a) the reference of the method used; b) the results and the form in which they are expressed; c) any particular details noted during the test; d) any operations not specified in this International Standard or any optional operations. 5 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
