1、Designation: D 1844 86 (Reapproved 2003)Standard Test Methods forChemical Analysis of Basic Lead Silicochromate1This standard is issued under the fixed designation D 1844; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the chemical analysis of thepigment commercially known as basic lead silicochromate andare
3、applicable to pigment supplied by the manufacturer and topigment, but not mixed pigments, separated from liquidcoatings. The presence of basic lead silicochromate speciesshall be confirmed by X-ray diffraction analysis (see Specifi-cation D 1648).1.2 For liquid coatings the pigment must first be sep
4、aratedfrom the vehicle before conducting the analysis.1.3 The analytical procedures appear in the following order:SectionsLead oxide 6 to 14Chromium trioxide 15 to 23Silica 24 to 27Moisture and other volatile matter 28Coarse particles 29Oil absorption 30Mass color and tinting strength 311.4 The valu
5、es stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and
6、health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 185 Test Methods for Coarse Particles in Pigments,Pastes, and PaintsD 280 Test Methods for Hygroscopic Moisture (and OtherMatter Volatile Under the Test Conditions) in
7、PigmentsD 281 Test Method for Oil Absorption of Pigments bySpatula Rub-OutD 387 Test Method for Color and Strength of Color Pig-ments with a Mechanical MullerD 1193 Specification for Reagent WaterD 1648 Specification for Basic Lead Silicochromate Pig-mentD 2371 Test Method for Pigment Content of Sol
8、vent-Reducible Paints3. Significance and Use3.1 These test methods may be used to confirm the statedlead oxide, chromium trioxide and silica content of basic leadsilicochromate and is useful for quality control.4. Purity of Reagents4.1 Reagent grade chemicals shall be used in all tests.Unless otherw
9、ise indicated, it is intended that all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society, where suchspecifications are available.3Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficientlyhigh puri
10、ty to permit its use without lessening the accuracy ofthe determination.4.2 Unless otherwise indicated, references to water shall beunderstood to mean reagent water conforming to Type II ofSpecification D 1193.5. Preparation of Sample5.1 Thoroughly mix liquid coatings and separate in accor-dance wit
11、h Test Method D 2371 sufficient pigment to enablethe required analyses to be carried out.1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings, Materials, and Applications and are the directresponsibility of Subcommittee D01.31 on Pigment Specifications.Cu
12、rrent edition approved Dec. 1, 2003. Published December 2003. Originallyapproved in 1961. Last previous edition approved in 1986 as D 1844 86 (1999).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStanda
13、rds volume information, refer to the standards Document Summary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards
14、for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc., (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Thoroughl
15、y mix pigment supplied as such and grindseparated pigment to a fine powder in a mortar and pestlebefore taking portions for analysis.TOTAL LEAD AS LEAD OXIDE-GRAVIMETRICMETHOD6. Apparatus6.1 Glass Filtering Crucible (medium-porosity fritteddisk), dried to constant weight before use.6.2 Platinum Dish
16、.7. Reagents7.1 Acetic Acid (Glacial).7.2 Ammonium Hydroxide (sp gr 0.90)Concentrated am-monium hydroxide (NH4OH).7.3 Ammonium Acetate, Acid SolutionTo 300 mL of wateradd an equal volume of NH4OH. Neutralize with glacial aceticacid and add 20 mL in excess.7.4 Hydrochloric Acid (sp gr 1.19)Concentrat
17、ed hydro-chloric acid (HCl).7.5 Hydrofluoric Acid (47 %)Concentrated hydrofluoricacid (HF).7.6 Hydrogen Sulfide (H2S)Handle and use H2S in hood.7.7 Isopropyl Alcohol (50 and 98 %).7.8 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3) (see 7.4.1).7.9 Potassium Dichromate Solution (saturated)Prep
18、are asaturated solution of potassium dichromate (K2Cr2O7) in water.7.10 Sulfuric Acid (1 + 1)Carefully mix 1 volume ofconcentrated sulfuric acid (H2SO4, sp gr 1.84) with 1 volumeof water (see 7.4.1).8. Procedure8.1 Weigh accurately (to 0.1 mg) 1 g of the sample into aplatinum dish. Add 5 mL of HNO3a
19、nd 10 mL of HF.Cautiously evaporate to dryness on a steam bath. Repeat theaddition of HNO3and HF and again cautiously evaporate todryness. Wash the sides of the dish with a little water andevaporate to dryness. Wet the residue with 5 mL of HNO3,warm gently, and transfer the residue to a 400-mL beake
20、r usinga policeman. Neutralize with NH4OH, and then make thesolution just acid with HCl, adding 5 mL in excess. Dilute to200 mL and heat to just below the boiling point until solutionis complete.8.2 Pass H2S through the solution for about 20 min. Filter,using paper pulp. Wash the precipitate five to
21、 six times withwater just acid with HCl and saturated with H2S. Transfer thepaper and precipitate to the original beaker, add 25 mL ofHNO3, boil until the residue is white, then add 10 mL of H2SO4(1 + 1). Destroy the organic material by evaporating thesolution to dense white fumes, making further ad
22、ditions ofHNO3until there is no charring.8.3 Cool the solution, add 10 mL of water, and evaporate tofumes. Repeat the addition of water and the evaporation. Coolthe solution, add 40 mL of water, and bring the solution toboiling. Cool the solution and add 50 mL of isopropyl alcohol(98 %), stir, and a
23、llow the solution to stand cold for at least 4h. Filter, using paper pulp, and wash once with cold isopropylalcohol (50 %) containing 10 mL of H2SO4(sp gr 1.84)/100mL.8.4 Transfer the precipitate to the original beaker with 150mL of water, add 50 mL of the ammonium acetate solution, andboil the solu
24、tion until the lead sulfate dissolves. Filter while hotthrough the original paper and wash well (6 to 8 washes) withhot water. To the filtrate add 5 mL of glacial acetic acid, heatthe solution to boiling, and add 20 mL of saturated K2Cr2O7solution. Boil the solution until the precipitate turns orang
25、e,and allow to stand on a warm plate for at least 2 h. Filterthrough a glass filtering crucible (medium-porosity fritteddisk), wash three times with hot water, and finally once withalcohol. Dry in an oven at 105C for 2 h, cool, and weigh.9. Calculation9.1 Calculate the percent of total lead as lead
26、oxide (PbO) asfollows:PbO, % 5 P 3 69.06!/Swhere:P = lead chromate (PbCrO4) precipitate, g,S = sample used, g, andmolecular weight PbO!molecular weight PbCrO45223.21323.215 0.6906 3 100 for percent!569.0669.06 represents the gravimetric factor to convert grams ofPbCrO4to grams of PbO.This gravimetri
27、c factor has led to high results due to thepresence of mixed lead chromates and an empirical factor canbe used to compensate:Empirical factor 5 69.06 3 0.9944 5 68.67ALTERNATIVE METHOD FOR TOTAL LEAD ASLEAD OXIDETITRIMETRIC METHOD10. Apparatus10.1 Platinum Dish.10.2 Filter Paper, ashless, medium tex
28、ture, or paper pulp.11. Reagents11.1 Ammonium Hydroxide (sp gr 0.90)Concentrated am-monium hydroxide (NH4OH).11.2 Glacial Acetic Acid (min 99.7 %)Concentrated gla-cial acetic acid (CH3COOH).11.3 Acid Ammonium Acetate BufferMix 400 mL ofdistilled water and 400 mL of ammonium hydroxide (sp gr0.90). Ad
29、d 375 mL of reagent grade glacial acetic acid slowlywhile stirring.11.4 Cupric Sulfate Solution (0.1M)Dissolve 25 g ofCuSO45H2O in distilled water and dilute to 1 L.11.5 Disodium Ethylenediaminetetracetate Dihydrate (0.05M) (EDTA solution)4Dissolve 18.6 g of the salt in distilledwater and dilute to
30、1 L. Standardize the solution as follows:4The standardized solution may also be purchased from Corco Chemical Corp.Catalog No.Special.D 1844 86 (2003)2Transfer 25 mL of lead standard (11.14) to a 400-mL beaker.Add concentrated ammonium hydroxide (11.1) dropwise untila permanent precipitate just form
31、s. Add 25 mL of acidammonium acetate (11.3), dilute to 200 mL, heat to boiling,add 4 drops of copper EDTA (11.7) and 12 drops of PAN(11.13) and titrate with the EDTA to a clear yellow.1mLNa2EDTA 5 0.2790/V g PbOwhere:V = EDTA required for titration, mLg = lead oxide, g, and0.05 M 3 0.22321 = 0.01116
32、 g PbO in 1 mL of lead standard(10.14) (25 mL) (0.05 M) (0.22321) = 0.2790 g PbO in 25 mLof lead standard (10.14).11.6 Murexide Indicator TabletsAmmonium salt of pur-puric acid.11.7 Copper-EDTA SolutionMix equivalent amounts ofcupric sulfate solution (11.4) and EDTA solution (11.5) andstore in a dro
33、pping bottle. The cupric sulfate EDTA equiva-lence may be determined as follows: Pipet 10 mL of cupricsulfate into a beaker, add concentrated ammonium hydroxidedropwise until the precipitate which forms just redissolves.Dilute to 200 mL with water, add two Murexide indicatortablets, and titrate imme
34、diately with EDTA to a color changefrom yellow to purple.11.8 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl) (see 7.4.1).11.9 Hydrofluoric Acid (47 %)Concentrated hydrofluoricacid (HF).11.10 Hydrogen Sulfide (H2S)Cylinder. Handle and use ina hood.11.11 Hydrogen Sulfide Wash Solu
35、tion Add 10 mL of HCl(sp gr 1.19) to 1 L of water and saturate with H2S.11.12 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).11.13 Pan Indicator (1-(2-pyridylazo)-2-naphthol)Dissolve 0.1 g in 100 mL of ethanol.11.14 Primary Standard (0.05 M lead nitrate)Dissolve16.5615 g of reagent grade lea
36、d nitrate in distilled water anddilute to 1 L.1mL5 0.01116 g PbO11.15 Sulfuric Acid (1 + 1)Carefully mix 1 volume ofconcentrated sulfuric acid (H2SO4, sp gr 1.84) with 1 volumeof water.12. Procedure12.1 Dissolve1gofpigment in accordance with 8.1 and8.2.12.2 Cool, so that the addition of 25 mL of wat
37、er does notcause excessive splattering of the sulfuric acid; the solution atthis point should be water white. Add ammonium hydroxide(sp gr 0.90) until the pH of the solution is 5 to 5.5 (as indicatedby pH paper). Add 50 mL of acid ammonium acetate (11.3),boil 5 min, dilute to 200 mL with water, heat
38、 to boiling, add 4drops of copper-EDTA (11.7) and 12 drops of PAN(11.1311.13) and titrate while hot with standard EDTA to aclear yellow.13. Calculation13.1 Calculate the percent lead oxide as follows:PbO, % 5V 3 L 3 100Swhere:V = EDTA required for titration, mL,L = lead equivalent of EDTA solution,
39、andS = specimen weight, g.14. Precision and Bias14.1 On the basis of an interlaboratory study of the methodin which operators in three laboratories analyzed two paintscontaining basic lead silicochromate with iron oxide thefollowing criteria should be used for judging the acceptabilityof the results
40、 at the 95 % confidence level:14.1.1 RepeatabilityTwo results, each the mean of dupli-cate determinations obtained by the same operator should beconsidered suspect if they differ by more than the following:Percent Absolute PbO28 %45 %0.200.3014.1.2 ReproducibilityA realistic range could not be es-ta
41、blished for results between laboratories because of thelimited number of participating laboratories.14.1.3 BiasA bias statement could not be establishedbecause of the limited number of participating laboratories.CHROMIUM TRIOXIDE15. Interference15.1 Soluble Fe+3will cause high results. See Section 2
42、0.16. Reagents16.1 Potassium Dichromate, Standard Solution (0.1 N)Weigh 4.904 g of dried potassium dichromate (K2Cr2O7),dissolve it in water, and dilute to 1 L with water in a volumetricflask.16.2 Potassium Iodide Solution (150 g/L)Dissolve 150 gof potassium iodide (KI) in water and dilute to 1 L.16
43、.3 Hydrochloric Acid MixtureSaturate water with NaCl(about 350 g/L). To each litre of this solution add 150 mL ofwater and 100 mL of concentrated HCl (sp gr 1.19).16.4 Sodium Thiosulfate Solution (0.1 N)Dissolve 24.8 gof reagent grade Na2S2O35H2O in recently boiled water anddilute to 1 L with additi
44、onal recently boiled water. To stan-dardize, pipet 25 mL of the standard potassium dichromatesolution (exactly 0.1000 N) into a 250-mL Erlenmeyer flask.Add 100 mL of water, 15 mL of potassium iodide solution, and15 mL of concentrated hydrochloric acid (sp gr 1.19). Titratethe liberated iodine with s
45、odium thiosulfate solution until thereddish-brown color becomes quite faint. Add 5 mL of starchsolution and continue the titration dropwise until the blue colorchanges to a pale green. Calculate the normality of the sodiumthiosulfate solution as follows:N 52.5000MD 1844 86 (2003)3where:N = normality
46、, andM = sodium thiosulfate solution, mL,16.5 Starch Indicator SolutionMake a homogeneouspaste of 10 g of soluble starch in cold water. Add to this 1 L ofboiling water, stir rapidly, and cool. Salicylic acid (1.25 g/L)may be added to preserve the indicator. If long storage isrequired, the solution s
47、hould be kept in a refrigerator at 4 to10C (40 to 50F). Prepare fresh indicator when the end pointof the titration from blue to colorless or blue to light green failsto be sharp.17. Procedure17.1 Weigh to 0.1 mg about1gofsample into a 500-mLErlenmeyer flask. Add 100 mL of NaCl-HCl solution anddissol
48、ve the sample without heat, keeping the solution cold.(Silica will not dissolve, but it does not interfere with theanalysis.) Add 10 mL of KI solution and titrate with 0.1 Nsodium thiosulfate solution until the reddish-brown color isalmost gone. Add 5 mL of starch solution and titrate slowly,dropwis
49、e, until the blue color changes to a light green.18. Calculation18.1 Calculate the percent of chromium trioxide (CrO3)asfollows:CrO3,%5 V1N 3 0.03334!/S2# 3 100where:V1= sodium thiosulfate solution required for titration ofthe specimen, mLN = normality of the sodium thiosulfate solution,S1= sample used, g, and1 6CrO3 Cr13milliequivalent weight5molecular weight CrO31000 3 3 valence!599.991000 3 35 0.03334 (1)ALTERNATIVE METHOD FOR CHROMIUMTRIOXIDE19. Scope19.1 This test method determines total chromium as chro-mium trioxide. Iron oxide
