1、International Standard INTERNATIONAL ORGANIZATION FOR STANOAROIZATION.MEYHAPOHAfl OPrAHH3AUHR llOCTAH b) barytes-reduced lithopones, which consist of mixtures of lithopones with higher zinc sulphide content and ground mineral barytes. These products should be marked so as to indicate the presence of
2、 barytes. 1 IS0 473-1982 (E) Table - Required characteristics and their tolerances 6.1.1.1 Preparation L Characteristic Requirement Test method Total zinc, calculated as zinc sulphide % (mlm) min. lithopone 30 % lithopone 60 % Zinc oxide, % (m/ml max. Sum of total zinc, cal- culated as zinc sulphide
3、, and barium sulphate, % tmlml min. Matter volatile at 105 OC % (m/ml max. Matter soluble in water, % tmlm) max. Residue on sieve (63 urn), % (m/m) max. 28 58 1 99 O,5 03 0.1 Clause 6 Clause 7 Clause 6 IS0 78712 IS0 787/3 IS0 78717 Colour Alkalinity of the aqueous extract Oil absorption value Lighte
4、ning power Hiding power Closely matching that of the agreed sample IS0 787/l Closely matching that IS0 78714 of the agreed sample To be agreed between the IS0 787/5 interested parties To be agreed between the IS0 787117 interested parties To be agreed between the To be agree1 interested parties d Me
5、thods of test During the analyses, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 6 Determination of barium sulphate and total zinc content 6.1 Reagents 6.1.1 Potassium hexacyanoferrate(ll),l) standard volu- metric solution cK4Fe(CN)el = 0,05
6、 mol/l (titre Texpressed in grams of zinc per millilitre). Dissolve 21,0 g of potassium hexacyanoferrate(ll1, 300 mg of potassium hexacyanoferrate(lll)2) and 2 g of anhydrous sodium carbonate (to stabilize the solution) in water and dilute to 1 000 ml in a one-mark volumetric flask. 6.1.1.2 Standard
7、ization Pipette 25,0 ml of the zinc chloride solution (6.1.2) into a flask and add ammonia solution (6.1.6) until a piece of Congo red paper (6.1.81, when touched with the solution, just turns to a pure red colour. Then carefully neutralize the solution with the hydrochloric acid solution (6.1.3) fr
8、om a dropping bottle. Add a few drops in excess until the Congo red paper turns to a lasting red-blue or blue-red colour (pH I,5 to 3,O). Make up to 150 ml with water, heat the solution to boiling, and add 10 drops of the diphenylamine solution (6.1.7). Immediately titrate the solution with the pota
9、ssium hexa- cyanoferrate(ll) solution (6.1.1.1) until the colour turns to a lasting yellow or yellowish green. Then back-titrate the solution with the zinc chloride solution (6.1.2) until the colour just turns to blue again. 6.1.1.3 Calculation of titre Calculate the titre Tof the potassium hexacyan
10、oferrate(ll) solu- tion, expressed in grams of zinc per millilitre, by using the formula c (25 + V, Vl where c is the concentration, in grams of zinc per millilitre, of the standard zinc chloride solution (6.1.2); VI is the volume, in millilitres, of the potassium hexa- cyanoferrate(ll1 solution (6.
11、1.1.1) required for the titration; V2 is the volume, in millilitres, of the standard zinc chloride solution (6.1.2) required for the back-titration. 6.1.2 Zinc chloride, standard reference solution, containing approximately 5 g of zinc per litre (concentration c, in grams of zinc per millilitre). We
12、igh about 5 g of chemically pure zinc to the nearest 0,l mg, dissolve in 300 ml of the hydrochloric acid solution (6.1.3) and dilute the solution obtained with water to 1 000 ml in a one- mark volumetric flask. 1) IUPAC name; formerly called potassium ferrocyanide, K4Fe(CN)a. 2) IUPAC name; formerly
13、 called potassium ferricyanide, KaFe(CN)a. 2 6.1.3 6.1.4 6.1.6 6.1.6 6.1.7 6.16 6.16 Hydrochloric acid, 4 mol/l solution. Sulphuric acid, 2 mol/l solution. Ammonia, solution, Q = 0,9 g/ml. Ammonia, 4 mol/l solution. Diphenylamine, 50 g/l ethanolic solution. Congo red paper. Lead acetate paper. 6.2 P
14、rocedure Weigh, to the nearest 0.1 mg, about 0,6 g of lithopone 30 % previously dried at 105 f 2 OC or about 0,3 g of lithopone 60 % previously dried at 105 f 2 OC into a beaker and add 25 ml of the hydrochloric acid solution (6.1.3). Immediately cover with a watch-glass and boil until the evolution
15、 of hydrogen sulphide has ceased test with lead acetate paper (6.1.911. Dilute with 100 ml of water, add 5 ml of the sulphuric acid solution (6.1.4) and boil the solution again. Allow the precipitate to settle whilst hot and filter the superna- tant solution through a fine filter paper. Transfer the
16、 precipitate to the filter paper and wash with hot water containing some sulphuric acid until a drop of the washings shows no reaction with the potassium hexacyanoferrate(ll) solution (6.1.1). Fold the filter paper over the precipitate. Transfer it whilst still wet to a weighed porcelain crucible an
17、d ignite it in contact with air to constant mass. The residue is assumed to be barium sulphate.1) Add a few drops of the sulphuric acid solution to the contents of the crucible. No trace of hydrogen sulphide should be noticeable; otherwise, the sulphuric acid shall be driven off and the residue re-i
18、gnited. Combine the washings with the filtrate. Add a slight excess of the ammonia solution (6.1.5) verify on Congo red paper (6.1.811, followed by the hydrochloric acid solution from a dropping bottle until a small piece of Congo red paper, when touched with the solution, just turns to a lasting re
19、d-blue or blue-red colour (pH I,5 to 3,O). /- - If necessarv, make UD to 150 ml with water, heat the solution to boiling, add.10 drops of the diphenylamine solution (6.1.7) and immediately titrate the solution as specified for the standardiza- tion of the potassium hexacyanoferrate(ll1 solution in 6
20、.1.1.2. 6.3 Expression of results Calculate the barium sulphate content of the lithopone, ex- pressed as a percentage by mass, by the formula 100 m2 IS0 473-1982 (E) Calculate the total zinc content of the lithopone, expressed as a percentage by mass, calculated as zinc sulphide, by the formula 1,49
21、0 (TV-3 -cv, 00 = 49(TV, -cv, ml 31 where m, is the mass, in grams, of the test portion; m2 is the mass, in grams, of the residue; T is the titre, expressed in grams of zinc per millilitre, of the potassium hexacyanoferrate(ll) solution (6.1.11, as calculated in 6.1 .I .3; c is the concentration, in
22、 grams of zinc per millilitre, of the standard zinc chloride solution (6.1.2); Vs is the volume, in millilitres, of the potassium hexa- cyanoferrate(ll) solution (6.1.1) required for the titration; V4 is the volume, in millilitres, of the standard zinc chloride solution (6.1.2) required for the back
23、-titration. 7 Determination of the zinc oxide content 7.1 Reagents 7.1.1 Ammonium chloride. 7.1.2 Potassium hexacyanoferratefll), standard volu- metric solution cK4Fe(CN)sl = 0,05 mol/l (titre ZI, prepared as specified in 6.1.1.1 and standardized as specified in 6.1.1.2. 7.1.3 Zinc chloride, standar
24、d reference solution containing approximately 5 g of zinc per litre (concentration cl, prepared as specified in 6.1.2. 7.1.4 7.1.5 7.1.6 7.1.7 Hydrochloric acid, 4 mol/l solution. Ammonia, 4 mol/l solution. Diphenylamine, 50 g/l ethanolic solution. Congo red paper. 7.2 Procedure Weigh, to the neares
25、t 1 mg, about 10 g of the lithopone previously dried at 105 + 2 OC into a 500 ml one-mark volumetric flask. Add 4 g of the ammonium chloride (7.1.1) and 100 ml of the ammonia solution (7.1.5). Allow the suspension to stand for 1 h in the cold, shaking at intervals. After this period make the suspens
26、ion up to the mark with water, shake 1) If desired, the actual barium sulphate content can be determined by fusing the residue with potassium sodium carbonate and converting the barium carbonate into barium sulphate. 3 IS0 473-1982 (E) and filter through an absolutely dry filter paper and funnel. Di
27、scard the first 10 to 20 ml of the filtrate and collect the re- mainder in a dry beaker. Transfer 250 ml of this filtrate to a beaker by means of a pipette and add to it 10 ml of the zinc chloride solution (7.1.3) followed by the hydrochloric acid solu- tion (7.1.4) from a dropping bottle until a pi
28、ece of the Congo red paper (7.1.7), when touched with the solution, turns to a lasting red-blue or blue-red colour (pH 1,5 to 3,O). Heat the solution to boiling, add 10 drops of the diphenylamine solution (7.1.6) and immediately titrate the solution as specified for the standardization of the potass
29、ium hexacyanoferrate(ll) solution in 6.1.1.2. 7.3 Expression of results Calculate the zinc oxide content of the lithopone, expressed as a percentage by mass, by the formula 100 246 2,4!N(TV5-cVs-loc)-=-(TV5-cVs-10c) m3 “3 where T is the titre, expressed in grams of zinc per millilitre, of the potass
30、ium hexacyanoferrate(ll) solution (7.1.2); c is the concentration, in grams of zinc per millilitre, of the standard zinc chloride solution (7.1.3); ks is the volume, in millilitres, of the potassium hexa- cyanoferrate(ll1 solution (7.1.2) required for the titration; Ls is the volume, in millilitres,
31、 of the standard zinc chloride solution (7.1.3) required for the back-titration. 8 Test report The test report shall contain at least the following information : a) the type and identification of the product tested; b) a reference to this International Standard (IS0 473); c) the results of the tests, and whether or not the product complies with the relevant specification limits; d) any deviation, by agreement or otherwise, from the procedures specified; m3 is the mass, in grams, of the test portion; 4 e) the date of the tests.
