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ASTM D444-88(R2020) pdf free download

ASTM D444-88(R2020) pdf free download.Standard Test Methods for Chemical Analysis of Zinc Yellow Pigment (Zinc Chromate Yellow)
8. Procedure
8.1 Weigh to 0.1 mg 3 g of the oven-dried material from the determination ofmoisture and other volatile matter (Note 2 and Note 3), and place in a porcelain boat. Introduce the boat with the charge into a refractory combustion tube in an electrically- heated combustion furnace of the type used for the determina- tion of carbon in steel by direct combustion (Note 4). Place the boat at the center of the combustion tube maintained at a temperature of 1000°C for 4 h. Draw a current of pure dry air or dry nitrogen through the tube to sweep the evolved moisture into a previously weighed absorption tube containing anhy- drous magnesium perchlorate (Mg(ClO 4 ) 2 ) or other efficient desiccant. The weight increase of the absorption tube repre- sents the “combined water.” N OTE 2—Loss on ignition of the pigment does not suffice for the determination of combined water in zinc yellow. N OTE 3—If the pigment contains an organic treating agent, first remove this treating agent by washing with ether or chloroform. N OTE 4—See Apparatus No. 1 for the determination of total carbon by direct combustion as described in Practices E50.
13. Procedure
13.1 Pipet a 25-mL aliquot of the solution of the specimen (Section 9) into a 500-mL glass-stoppered Erlenmeyer iodime- tric flask or other suitable glass-stoppered bottle containing 200 mL of H 2 SO 4 (1+39). Add 20 mL of KI solution (150 g/L), stopper, and allow the solution to stand for approximately 5 min. 13.2 Titrate the liberated iodine with 0.1 NNa 2 S 2 O 3 solution at room temperature until the reddish brown iodine color becomes quite faint. Add 5 mL of starch solution and continue the titration until the final color change becomes pale green with no blue tinge. Titrate this final titration by swirling the flask at least three times after each addition of the Na 2 S 2 O 3 solution, being sure that there is no further color change, especially at the final stage ofthe titration. The green end point is definite and sharp.
16. Reagents
16.1 Methyl Orange Indicator Solution—Dissolve 0.1 g of methyl orange in 100 mL of water. 16.2 Potassium Ferrocyanide, Standard Solution—Dissolve 22 g of potassium ferrocyanide (K 4 Fe(CN) 6 · 3H 2 O) in water and dilute to 1 L. To standardize, transfer 0.2 g ofmetallic zinc or freshly ignited ZnO to a 400-mL beaker. Dissolve in 10 mL of hydrochloric acid (HCl, sp gr 1.19) and 20 mL of water. Drop in a small piece of litmus paper, add ammonium hydroxide (NH 4 OH) until slightly alkaline, then add HCl until just acid, and then 3 mL more of HCl. Dilute to about 250 mL with hot water and heat nearly to boiling. Run in the K 4 Fe(CN) 6 solution slowly from a buret, while stirring constantly, until a drop tested on a white porcelain plate with a drop of the uranyl indicator solution shows a brown tinge after standing 1 min. Do not allow the temperature of the solution to fall below 70°C during the titration. Run a blank using the same amounts of reagents and water as in the standardization. The standardization must be made under the same conditions of temperature, volume, and acidity as obtained when the specimen is titrated. Calculate the strength of the K 4 Fe(CN) 6 solution in terms of grams of zinc as follows:
21. Procedure
21.1 For this determination take about 20 g of Type I pigment or about 5 g of Type II pigment as defined in Specification D478. Weigh the specimen into a 1-Lbeaker. Add 75 mL of HCl (sp gr 1.19). Boil the solution under a hood until the rapid evolution of chlorine has subsided. Add 5 mL of methyl alcohol and boil to a volume of about 35 mL (Note 9). Add 25 mL of HCl and continue boiling. Add 5 mL of methyl alcohol and again boil to a volume of about 35 mL. N OTE 9—Ifthe volume is reduced below 35 mL, a precipitate may form that will not dissolve upon dilution. It is imperative, however, that all the chromium be reduced. 21.2 Dilute the solution to 400 mL with water. If the solution is not clear at this point, filter it. Heat to boiling and add 50 mL of glacial acetic acid. Add 10 mL of BaCl 2 solution (100 g/L) dropwise, while stirring. Boil for 30 min and allow to stand overnight (Note 10). Filter through a tared Gooch crucible and wash with hot water. N OTE 10—The acetic acid is necessary to minimize the tendency of sulfate to form an inner complex with the trivalent chromium. It is necessary that the solution stand overnight to ensure the precipitation of all the sulfate. 21.3 Dry the precipitate in an oven, and ignite at 900°C to constant weight. Weigh as barium sulfate (BaSO 4 ). N OTE 11—If the wet precipitate has a yellow appearance, all the chromate was not previously reduced. The results will be high and the specimen should be discarded. Greater attention should then be given to the reduction of the chromium. A slight greenish color cannot be avoided but does not indicate a serious error.

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