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Titrimetric Determination of Hypo Index, Thiosulfate, and Sulfite in EASTMAN Color Films,
Process ECN-2 Fixer
ECN-0002/1
The thiosulfate is determined by the visual titration by
Process ECN-2 ECP-2D VNF-1/LC RVNP
adjusting the pH of a sample aliquot to 8.5. At this pH, the
Formulas F-34a/F-34aR — — —
sulfite rapidly forms the stable sulfite - formaldehyde
adduct. Upon acidification, which prevents the adduct from
INTRODUCTION
reacting with iodine, the thiosulfate from the sample is
This me
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additions of 34.57 g/L thiosulfate ion and 5.444 g/L sodium sulfite were made to that “seasoned” sample. POTENTIOMETRIC TITRATION STATISTICS Repeatability Standard Deviation, 1s & 95 Percent r Confidence Estimate (not including bias) Repeatability standard deviation is an estimate of the variability one trained analyst should be able to obtain under favorable conditions (analyzing a sample, with one instrument, within one day). The 95 percent confidence estimate (calculated using the repea
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Recovery Recovery is used instead of bias for “seasoned” samples, since the component concentration level was not determined independently of the test method. It is defined as the calculated mean for the “seasoned” sample with a standard addition of the component minus the mean for the “seasoned” sample, divided by the actual amount of the standard addition. It is expressed as a percentage. The table below shows whether or not a recovery is statistically or practically different from 100
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VISUAL TITRATION STATISTICS Repeatability Standard Deviation, 1s and r 95 Percent Confidence Estimate Repeatability standard deviation is an estimate of the variability one trained analyst should be able to obtain under favorable conditions (analyzing a sample, with one instrument, within one day). HYPO INDEX (3.0 mL) Repeatability Standard 95 Percent Samples (Process Mean Level (N) Deviation, 1S Confidence Estimate r ECN-2 Fixer) (mL 0.1 N I ) 2 (mL 0.1 N I ) (mL 0.1 N I ) 2 2 “Fresh” at “
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Recovery Recovery is used instead of bias for “seasoned” samples, since the component concentration level was not determined independently of the test method. It is defined as the calculated mean for the “seasoned” sample with a standard addition of the component minus the mean for the “seasoned” sample, divided by the actual amount of the standard addition. It is expressed as a percentage. The table below show whether or not a recovery is statistically or practically significant from 100
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APPARATUS PROCEDURE All volumetric glassware should meet all “Class A” For Potentiometric Titration specifications, as defined by American Society for Testing A. Hypo Index (HI) or Total Reductants and Materials (ASTM) Standards E 287, E 288, and E 969, 1. To a 400-mL beaker with a magnetic stir-bar, add unless otherwise stated. 100 mL reagent water. For Potentiometric Titration: 2. Pipette 40.0 mL (use a 20-mL pipette, twice) of Metrohm Potentiograph, Model E536 or equivalent standardiz
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B. Thiosulfate Determination For Visual Titration 1. Sample Pretreatment: A. Hypo Index (HI) or Total Reductants a. To a 250-mL beaker with a magnetic stir-bar, Treatment and Titration of Sample: add 75 mL of reagent water. 1. Pipette (wipe before leveling) 40.0 mL of standardized 0.1 N potassium iodate solution into a 250-mL conical b. Pipette 2.0 mL of sample into the 250-mL flask containing a magnetic stir bar. beaker. 2. Add 10 mL of 2.0 N acetic acid solution from a tip-up c. Add 5 mL
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CALCULATIONS For Potentiometric Titration A. Hypo Index (HI) or Total Reductants: (mL Blank A – mL Sample A) (N Na S O ) 2 2 3 HI (1), mL = 0.1000 N Na S O 2 2 3 Where: HI (1), mL = mL of 0.1000 N I consumed by 1.0 mL 2 sample mL Blank A = millilitres of titrant at the end point of the blank titration of potentiometric Procedure A. mL Sample A = millilitres of titrant at the end point of the sample titration of potentiometric Procedure A. N Na S O = normality of the titrant (meq/mL) 2 2 3 0
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Example Potentiometric Calculations: Titration mL 0.1 N Na S O Titrant 2 2 3 Blank A = 40.50 Sample A = 21.85 Blank B = 40.55 Sample B = 19.80 Hypo Index (HI) or Total Reductants: (40.50 – 21.85)(0.0989) HI (1), mL = 0.1000 = 18.4 mL 0.1000 N I 2 = Thiosulfate (S O ): 2 3 (40.55 – 19.80)(0.0989)(112.13)(1000) = g/L S O = 2 3 (2.0)(1000) = 57.5 g/L Sodium Sulfite (Na SO ): 2 3 [(40.50 – 21.85)(2.0) – (40.55 – 19.80)](0.0989)(63.02)(1000) g/L Na SO = 2 3 (2.0)(1000) = 51.4 g/L Processing KODAK Mot
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For Visual Titration A. Hypo Index (HI) or Total Reductants: (mL Blank A – mL Sample A) (N Na S O ) 2 2 3 HI (1), mL = 0.1000 N Na S O 2 2 3 Where: HI (1), mL = mL of 0.1000 N I consumed by 1.0 mL 2 sample mL Blank A = millilitres of titrant at the end point of the blank visual titration, Procedure A. mL Sample A = millilitres of titrant at the end point of the sample visual titration, Procedure A. N Na S O = normality of the titrant (meq/mL) 2 2 3 0.1000 = nominal value for the normality of
