1、International Standard 6685 0 1 4lYb INTERNATIONAL ORGANIZATION FOR STANDARDlZATlONW4EWYHAPOLIHAR OPrAtlH3AUHR OCTAHAAPTM3AUWl.ORGANISATlON INTERNATIONALE DE NORMALISATION $3 u _( “$. $% I, 1 1”;. “*J ; , ! y.r 1, “: ij.kw ,. i Chemical products for industrial use - General method for determination
2、of iron content - l,lO-Phenanthroline spectrophotometric method Produits chimiques 2 usage industriel - M / ? /I ij$ py$ ., b) the reference of the general method used and of the In- ternational Standard relating to the product being analysed; c) the results and the method of expression used; d) any
3、 unusual features noted during the determination; e) any operation not included in this International Stan- dard or in the international Standard relating to the product being analysed, or regarded as optional. Table 2 Mean, pg of Fe/ml Relative standard deviation of repeatability* Relative standard
4、 deviation of reproducibility* * Standard deviation x loo Mean Aluminium sulphate Ammonium sulphate 2,209 3,874 6,833 1,552 3,973 5,375 l,oo 1,16 1,17 0.77 1,ll I,15 53 3,6 2.5 5,6 484 22 Disodium tetraborate 1,189 2,825 5,727 1.35 I,77 0.77 7.0 33 23 3 Copyright International Organization for Stand
5、ardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Annex Interferences A.1 Certain cations, notably tin(W), antimonyflli), an- timony(V), titanium, zirconium, ceriumflll) and bismuth, are hydrolysed in acetate solution
6、at about pH 4; they will, however, remain in solution if sufficient citrate or tartrate is pre- sent. Up to 100 mg of these cations will not be precipitated if sodium citrate (or tartrate) buffer solution is used instead of the acetate buffer solution (4.3). Colour development will be ac- celerated
7、if the temperature of the solution is raised to boiling point. If citrate or tartrate buffer solutions are used, it is essen- tial that the order of addition of reagents, specified in 6.4.1, be adhered to. The addition of citrate also prevents the formation of insoluble phosphates. A.2 In the presen
8、ce of aluminium, hydrolysis will occur if the general procedure is followed. Whilst this interference can be overcome by the substitution of citrate or tartrate buffer for acetate buffer (as in the case of presence of titanium or zir- conium), if colour development is carried out between pH 3,5 and
9、4,2, aluminium will not interfere (see IS0 805”). A.3 Cadmium, zinc, nickel, cobalt and copper form soluble complexes with l,lO-phenanthroline. If these metals are present, colour development is retarded and the absorbance is reduced. The minimum amount of the reagent (4.5) required for each 0,l mg
10、of iron present is 1,7 ml but, in the presence of these interfering metals, additional reagent is required. Addi- tional reagents should be used in the proportion of 1 ml for each 0,l mg of nickel, cobalt or copper, each 0,5 mg of zinc and each 3 mg of cadmium. A.4 Solutions containing coloured ions
11、 cannot be measured against water. A solution of the same composition as that of the test solution, but without the l,lO-phenanthroline solution, should be used in the reference cell. A.5 In the presence of tungsten(V) or molybdenumWl), particularly in large amounts, the reaction should be carried o
12、ut at about pH 7, by introducing the following modifications : To the test solution containing tungsten or molybdenum, add 1 ml of a 300 g/l tartaric acid solution and adjust with the hydrochloric acid solution (4.1) or the ammonia solution (4.2) until only slightly alkaline to litmus. Add 1 to 2 ml
13、 of the am- monia solution (4.2) in excess, dilute to about 75 ml, add 1 ml of the ascorbic acid solution (4.4) and 10 ml of the reagent (4.51, heat for 5 to 10 min, at between 90 and 100 OC, cool to room temperature, and dilute to 100 ml. Using this method, up to 250 mg of tungsten or molybdenum in
14、 the test solution does not interfere. A.6 Silver forms an unstable complex with the reagent and hydrochloric acid, but this can be prevented by the addition of thiosulphate by the following procedure : Precipitate all the silver by adding sufficient sodium chloride solution. Adjust the pH to betwee
15、n 3 and 5, and add the ascor- bic acid and buffer solution as specified in 6.3.2. Then add a 25 g/l solution of sodium thiosulphate pentahydrate until the precipitate just dissolves, add IO ml of the reagent (4.5) and continue as specified in 6.3.2. Using this method, up to 100 mg of silver in the t
16、est solution does not interfere. A.7 If mercury(l) or mercuryfIll is present in the test solu- tion, then chloride cannot be tolerated. Adjustment of pH should, in these circumstances, be carried out with a 252 g/l nitric acid solution and, for each 5 mg of mercury present in the test solution, 10 m
17、l of the reagent solution (4.5) in addition to that specified should be used. A.8 More than 10 mg of rhenium in the test solution forms a precipitate of l,lO-phenanthrolinium perrhenate. A.9 The presence of pyrophosphate ions slows down col- our development and affects the reduction of iron(lll) to
18、iron(ll). Up to 2 mg in the test solution does not cause serious interference if absorbances are read after 30 min. Colour development can be accelerated by raising the pH; at pH 8,8, up to 30 mg of pyrophosphate in the test solution can be tolerated. A.10 Up to 500 mg of oxalates in the test soluti
19、on can be tolerated, above which colour development tends to be in- complete. A.11 Up to 250 mg of fluorides in the test solution can be tolerated, above which colour development tends to be in- complete. The reduction of iron(lll) to iron is affected. A.12 Up to 200 mg of vanadium(V) in the test so
20、lution does not interfere. A.13 Any selenite present in the test solution should be oxidized to selenate. Up to 1 000 mg of selenate does not interfere. A.14 Up to 1 mg of cyanide does not interfere.-. * IS0 805, Aluminium oxide primarily used for the production of aluminium - Determination of iron content - 1, lo-Phenanthroline photometric method. 4 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
