ASTM D3280-85(R2020) pdf free download

ASTM D3280-85(R2020) pdf free download.Standard Test Methods for Analysis of White Zinc Pigments
4. Significance and Use
4.1 White zinc pigments find considerable use in white paints, and as such it is useful to formulators and users to be able to monitor the amounts of these pigments in whole paints. It is also of interest to raw material suppliers and paint producers to check the specifications of each pigment.
5. Reagents
5.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Commit- tee on Analytical Reagents of the American Chemical Society, where such specifications are available. 3 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination. 5.2 Purity ofWater—Unless otherwise indicated, references to water shall be understood to mean Type II reagent grade water conforming to Specification D1193. 5.3 Concentration ofReagents: 5.3.1 Concentrated Acids and Ammonium Hydroxide— When acids and ammonium hydroxide are specified by name or chemical formula only it should be understood that concen- trated reagents of the following specific gravities or concen- trations are intended:
The desired specific gravities or concentrations of all other concentrated acids are stated whenever they are specified. 5.3.2 Diluted Acids and Ammonium Hydroxide— Concentrations of diluted acids and ammonium hydroxide, except when standardized, are specified as a ratio stating the number of volumes of the concentrated reagents to be diluted with a given number of volumes of water, as in the following example: HCl (1+99) means 1 volume of concentrated HCl (sp gr 1.19) diluted with 99 volumes of water.
6. Preparation of Sample
6.1 Grind dry pigments, if lumpy or not finely ground, to a fine powder for analysis. Large samples may be thoroughly mixed and a representative portion taken and powdered if lumpy or not finely ground. Mix the sample in all cases thoroughly before taking specimens for analysis. 6.2 Separate pigments from paints or pastes, grind to a fine powder, pass through a 180-µm (No. 80) sieve (Note 1) to remove any skins, thoroughly mix, and oven dry at 105°C. Moisten such pigments after weighing with a little alcohol before adding reagents for analysis. N OTE 1—Detailed requirements for this sieve are given in Specification E11. 6.3 Preserve all samples in stoppered bottles or containers.
7. Total Zinc, Using Diphenylamine as Internal Indicator
7.1 Reagents: 7.1.1 Diphenylamine Indicator Solution (10 g/L))— Dissolve 1 g of diphenylamine in 100 mL of H 2 SO 4 . 7.1.2 Potassium Ferrocyanide (1 mL = 0.008 g Zn)— Dissolve 35 g of K 4 Fe(CN) 6 ·3H 2 O in water and dilute to 1 L and add 0.3 g of potassium ferricyanide (K 3 Fe(CN) 6 ). Stan- dardize the solution by titrating against zinc (320 to 340 mg), following the procedure described in 7.2. Calculate the grams of zinc equivalent to 1.00 mL of the solution. 7.2 Procedure—Weigh to 0.1 mg about 0.4 g of the sample into a tall form 400-mL beaker. Moisten with about 20 mL of water, and dissolve in 15 mL of HCl. Neutralize with NH 4 OH, using litmus as the indicator. Add an excess of15 mL ofH 2 SO 4 (1+2) and dilute to 200 mL. Heat to approximately 60°C, add 2 drops of diphenylamine indicator solution and while stirring vigorously, titrate with K 4 Fe(CN) 6 solution to the color change from purple to a persistent yellowish green. N OTE 2—The true end point is a sharp, persistent change from a purple to a yellowish green. At the beginning of the titration, a deep blue color is developed after addition of a few millilitres of K 4 Fe(CN) 6 solution. About 0.5 to 1.0 mL before the true end point is reached, the solution changes from a blue to a purple color. After the purple color is developed, the titration should be continued dropwise to the persistent yellowish green end point.