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*Trademark of The Dow Chemical Company of 10

Copyright 2002 The Dow Chemical Company

ANALYTICAL METHOD

Effective: 08 April 96 DOWM 100896-TE96ASupersedes: DOWM 100896-TE91A

VERSENE 100 Chelating Agent

1. Scope

This method is applicable to the determination of chelation value, active ingredient, pH,specific gravity, and APHA color in VERSENE* 100 chelating agent over the rangesgiven in the table below (Note 13.1).

Test Item Applicable Range

Chelation Value 90 - 110 mg CaCO3/g chelating agentActive Ingredient 35.0 - 40.0 weight % as Na4EDTApH (1% solution) 10 - 12Specific Gravity 1.250 - 1.320

APHA Color 0 - 500

2. Principle

2.1 Chelation value: An aliquot of a sample of VERSENE 100 chelating agent isdissolved in water and sodium hydroxide (NaOH) is added to a pH of 11 to 12.Ammonium oxalate is added and the resulting mixture is titrated with calciumchloride solution to the first permanent turbidity.

2.2 Active ingredient: A calculated value is determined based on the chelation value.

2.3 pH: A 1% aqueous solution of VERSENE 100 chelating agent is prepared. ThepH of the solution is measured at 25°C with a pH meter with glass and referenceelectrodes. This procedure is based on ASTM E 70 (Section 14.1).

2.4 Specific gravity: The specific gravity in air is determined by means of ahydrometer at 25°C. This procedure is based on ASTM D 891 (Section 14.2).

08 April 96 2 of 10 pages DOWM 100896-TE96A

2.5 APHA Color: The transmittance of monochromatic light through the sample isrelated to its color by comparison with APHA standards. This procedure is basedon ASTM D 1209 (Section 14.3).

3. Safety

3.1 Each analyst should be acquainted with the potential hazards of the equipment,reagents, products, solvents, and procedures before beginning laboratory work.SOURCES OF INFORMATION INCLUDE: OPERATION MANUALS,MATERIAL SAFETY DATA SHEETS, LITERATURE AND OTHERRELATED DATA. Safety information for non-Dow products should berequested from the supplier. Disposal of waste materials, reagents, reactants, andsolvents must be in compliance with laws and regulations from all applicablegovernmental agencies.

3.2 Sodium hydroxide pellets and 50% caustic soda solution are highly corrosivematerials which can cause serious burns to the skin and eyes. Eye contact of onlya few seconds can cause permanent damage, even blindness. Consult the MaterialSafety Data sheets (Section 3.1) for these materials prior to use. Wearappropriate personal protective equipment.

4. Interferences

No direct interferences have been observed in the use of this method. If results aresuspect based on the analytical history of the product, the data should be confirmed by analternate method.

5. Apparatus

5.1 Analytical balance: capable of weighing to 0.0001 g, available from Mettler-Toledo Inc., PO Box 71, Hightstown, NJ 08520, or equivalent.

5.2 Indicating pH paper: for range 11 to 12, Alkacid Range 5 paper, available fromFisher Scientific, 711 Forbes Avenue, Pittsburgh, PA 15219, or equivalent.

5.3 Magnetic stirrer: with black top or black cover, Fisher Economy Stirrer, availablefrom Fisher Scientific, or equivalent.


5.4 pH Meter: with glass and reference electrodes, Corning model 130 pH meter,equipped with a Corning No. 476022 glass electrode and a Corning No. 476002reference electrode, available from Corning Inc., Science Products Div., HP-AB-03, Corning, NY 14831, or equivalent.

5.5 Water bath: capable of equilibrating at 25.0 ± 0.1°C, Haake RefrigeratingCirculator C1-K20, available from Fisher Scientific, or equivalent.

5.6 Hydrometer: with a range of 1.20 to 1.40, available from Fisher Scientific, orequivalent.

5.7 Colorimeter: Manostat model (used to be called Klett-Summerson), with a No.42 blue filter and a 4-cm cell, available from Curtin Matheson Scientific, PO Box1546, Houston, TX 77251, or equivalent.

5.8 Volumetric flask: 100-mL volume, available from Fisher Scientific, orequivalent.

6. Reagents

6.1 Ammonium oxalate: monohydrate, calcium free, ACS reagent grade, availablefrom Mallinckrodt, Inc., 675 Brown Road., St. Louis, MO 63134, or equivalent.

6.2 Ethylenediaminetetraacetic acid (EDTA): 99.99% purity or greater, Ultrapurereagent material such as Ultrex EDTA, available from J. T. Baker Inc., 222 RedSchool Lane, Phillipsburg, NJ 08865, or equivalent.

6.3 Calcium chloride dihydrate: ACS reagent grade, available from Mallinckrodt,Inc., or equivalent.

6.4 Sodium hydroxide pellets: ACS reagent grade, available from J. T. Baker Inc., orequivalent.

6.5 Deionized water: available from any reliable laboratory water purificationsystem, or from Fisher Scientific, or equivalent.

6.6 Platinum-cobalt color standard: 500 APHA, available from Aldrich ChemicalCo., Inc., 1001 W. St. Paul Avenue, PO Box 355, Milwaukee, WI 53201, orequivalent.


7. Reagent Solutions

7.1 Ammonium oxalate, 3% solution: Dissolve approximately 30 g of ammoniumoxalate (Section 6.1) in one liter of deionized water (Section 6.5) and mixthoroughly.

7.2 Calcium chloride, 0.5 M: Dissolve approximately 73.5 g of calcium chloridedihydrate (Section 6.3) in one liter of deionized water (Section 6.5). This solutionmust be standardized against standard EDTA as outlined in Section 8 prior to use.

7.3 50% Sodium hydroxide solution: Slowly dissolve approximately 500 g of sodiumhydroxide pellets (Section 6.4) in 500 mL of deionized water (Section 6.5).WARNING: This procedure is extremely exothermic and the solution willbecome quite hot. The pellets and solution are extremely corrosive. Wearthe proper protective equipment. Mix the resulting solution thoroughly andstore in a polyethylene bottle.

7.4 APHA color standards: Prepare standards having colors of 100, 200, 300 and 400by pipetting the volume of 500 APHA standard (Section 6.6) listed in the tablebelow into separate 100-mL volumetric flasks. Dilute each flask to volume withdeionized water (Section 6.5) and mix well.

APHA Standard to Prepare Volume of APHA 500 Standard to Add(mL)

100 20200 40300 60400 80

8. Standardization

Standardize the calcium chloride solution (Section 7.2) prior to use as follows:

8.1 Standardization solution:

8.1.1 Weigh (and record to the nearest 0.001 g) 2.5 to 3.0 g of Ultrapure EDTA(Section 6.2) into a 200-mL beaker.

8.1.2 Add 80 mL of deionized water (Section 6.5) and sufficient 50% sodiumhydroxide solution (Section 7.3) to the beaker in Section 8.1.1 to raise thepH to 11 to 12 (measure the pH with pH paper). Add 20 mL of 3%ammonium oxalate solution (Section 7.1) to the beaker.


8.1.3 Place the beaker on a magnetic stirrer which has a black top or cover andstir the resulting solution in Section 8.1.2 gently. Locate and utilize alight source so that the beaker is illuminated from behind.

8.2 Titrate the resulting standardization solution (Section 8.1.3) with the calciumchloride solution (Section 7.2) until the first permanent turbidity is noted.Perform the titration slowly, especially when nearing the endpoint. Measure thepH of the mixture with pH paper. The pH at this endpoint must be 11 or higher.If the pH is below 11, add enough 50% sodium hydroxide solution (Section 7.3) tobring the pH to above 11. If the turbidity disappears, continue the titration withcalcium chloride to the first permanent turbidity. Record the volume (mL) oftitrant required to reach the endpoint.

8.3 Calculate the molarity of the standardized calcium chloride as follows:

A BC

=

× 3422.

where:A = molarity (moles/L) of the calcium chloride solutionB = weight (g) of the EDTA sample titrated (Section 8.1.1)C = volume (mL) of the calcium chloride titrant used to reach the end point

of the standardization titration (Section 8.2)

3.422 = 1000292 2

mL Lg mole

/. /

292.2 = molecular weight (g/mole) of H4EDTA

9. Calibration

Calibrate the spectrophotometer prior to use as follows:

9.1 Zero spectrophotometer with deionized water (Section 6.5).

9.2 Analyze deionized water (Section 6.5) and each APHA standard solution (100 -500 APHA units; Sections 6.6 and 7.4) as follows: Pour each solution into aclean cell and insert the cell into the spectrophotometer so that the path length is 4cm. Record the reading.

9.3 Prepare a standard curve either by manually plotting the data (APHA units vs.reading) or by entering the data into a spreadsheet such as Excel and having thesoftware calculate the slope and intercept for the data.


10. Procedure

10.1 Determine the chelation value of the sample as follows:

10.1.1 Weigh (and record to the nearest 0.001 g) 8.0 + 0.3 g of the sample to beanalyzed into a clean 200-mL beaker.

10.1.2 Add 80 mL of deionized water (Section 6.5) and 20 mL of 3% ammoniumoxalate solution (Section 7.1) to the beaker in Section 10.1.1. Addsufficient 50% sodium hydroxide solution (Section 7.3) to the beaker toraise the pH to 11 to 12 (measure the pH with pH paper).

10.1.3 Place the beaker on a magnetic stirrer which has a black top or cover andstir the resulting solution in Section 10.1.2 gently. Locate and utilize alight source so that the beaker is illuminated from behind.

10.1.4 Titrate the resulting standardization solution (Section 10.1.3) with thestandardized calcium chloride solution (Section 7.2) until the firstpermanent turbidity is noted. Perform the titration slowly, especiallywhen nearing the endpoint. Measure the pH of the mixture with pH paper.The pH at this endpoint must be 11 or higher. If the pH is below 11, addenough 50% sodium hydroxide solution (Section 7.3) to bring the pH toabove 11. If the turbidity disappears, continue the titration with calciumchloride to the first permanent turbidity. Record the volume (mL) oftitrant required to reach the endpoint.

10.1.5 Calculate the chelation value for the sample as follows:

D E AF

=

× × 100

where:D = the chelation value for the sample (mg CaCO3 per g of chelating

agent)E = volume (mL) of calcium chloride titrant used to reach the end

point of the sample titration (Section 10.1.4)A = molarity (moles/L) of the calcium chloride solution (Section 8.3)F = weight (g) of sample titrated (Section 10.1.1)

100 = molecular weight (g/mole) of CaCO3


10.2 Determine the concentration (weight %) of active ingredient in the sample asfollows:

G E AF

=

× × 38

where:G = concentration (weight %) of active ingredient (as Na4EDTA) in the

sampleE = volume (mL) of calcium chloride titrant used to reach the end point

of the sample titration (Section 10.1.4)F = weight (g) of sample titrated (Section 10.1.1)

38 = molecular weight (g/mole) of Na4EDTA divided by 10

10.3 Determine the pH of the sample as follows:

10.3.1 Weigh 1.00 + 0.05 g of sample into a tared 250-mL beaker. Add 99.0 +0.1 g of deionized water (Section 6.5) to the beaker (the total weightshould be 100.0 ± 0.1 g.) and mix well.

Follow the manufacturer's instructions for the operation and calibration of the pH meter.Refer to ASTM E 70 for additional information on the subject (Section 14.1).

10.3.2 Equilibrate the temperature of the resulting solution in Section 10.3.1 to25°C using a water bath. Measure the pH of the solution at 25°C andreport the pH meter reading as the pH of the sample.

10.4 Determine the specific gravity of the sample at 25°C according to Method A ofASTM D 891 (Section 14.2).

Note: Method B of ASTM D 891 (Section 14.2) is an acceptable alternative but requiresadditional equipment.

10.5 Determine the APHA color of the sample as follows (Section 14.3):

10.5.1 Pour the sample into a clean cell. Insert the cell into thespectrophotometer so that the path length is 4 cm. Record the reading.


10.5.2 Either manually read the APHA color from a manually plotted graph(Section 9.3) or determine the APHA color value as follows:

APHA Color Value =

−R IS

where:R = reading recorded for the sample (Section 10.5.1)I = y-intercept of the standard curve (Section 9.3)S = slope of the standard curve (Section 9.3)

11. Precision (Note 13.2)

11.1 Chelation Value and Active Ingredient: Data obtained from multiple analyses[n(val) = 10] of a single sample on two separate days indicate a standard deviation[s(val)] of 0.060 weight % determined at an average concentration of 37.5 weight %Na4EDTA in VERSENE 100 chelating agent. The actual 95% confidenceinterval for the mean of the validation data [t s

n(n - 1)

(val)

(val )× where t(n-1) = 2.262] was

determined to be ± 0.043 weight %. Assuming a normal distribution of resultsand equal variability between laboratories, the 95% confidence interval for asingle value [1.96 s

n(val)

(analysis)× where n(analysis) = 1] is estimated to be ± 0.12 weight %.

11.2 Determination of pH: The procedure for pH measurement is essentiallyequivalent to ASTM E 70 (Section 14.1), with the exception of samplepreparation. The precision of the method should be equivalent to that reported inthe ASTM standard.

11.3 Determination of specific gravity: The procedure for specific gravitymeasurement is equivalent to ASTM D 891 (Section 14.2). The precision of themethod should be equivalent to that reported in the ASTM standard.

11.4 Determination of APHA color: The procedure for APHA color measurement isequivalent to ASTM D 1209 (Section 14.3). The precision of the method shouldbe equivalent to that reported in the ASTM standard.

12. Accuracy (Note 13.2)

12.1 Chelation Value and Active Ingredient: Analysis of four mixtures containing 40to 100 weight % chelating agent gave recoveries that averaged 100.0% with arange of 99.6 to 100.2% and a standard deviation of 0.16%.


12.2 Determination of pH: The procedure for pH measurement is essentiallyequivalent to ASTM E 70 (Section 14.1), with the exception of samplepreparation. The accuracy of the method should be equivalent to that reported inthe ASTM standard.

12.3 Determination of specific gravity: The procedure for pH measurement isequivalent to ASTM D 891 (Section 14.2). The accuracy of the method should beequivalent to that reported in the ASTM standard.

12.4 Determination of APHA color: The procedure for APHA color measurement isequivalent to ASTM D 1209 (Section 14.3). The accuracy of the method shouldbe equivalent to that reported in the ASTM standard.

13. Notes

13.1 The applicable ranges listed in Section 1 are estimates based on technicalexperience with the product and instrumentation. These estimates were madebecause the ranges studied during the method validation were limited. If resultsare suspect based on the analytical history of the product, the data should beconfirmed by an alternate method.

13.2 In accordance with good laboratory practices, it is strongly suggested that theprecision and accuracy of the method be re-determined if another set ofequipment is to be used or the method is to be used in another laboratory.

14. References

14.1 ASTM E 70-90 (or most current version), "Test Method for pH of AqueousSolutions with the Glass Electrode", available from American Society for Testingand Materials (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428.

14.2 ASTM D 891-95 (or most current version), "Standard Test Methods for SpecificGravity, Apparent, of Liquid Industrial Chemicals", available from AmericanSociety for Testing and Materials (ASTM).


14.3 ASTM D 1209-93 (or most current version), "Standard Test Methods for Color ofClear Liquids (Platinum-Cobalt Scale)", available from American Society forTesting and Materials (ASTM).

******************************************************************************THE INFORMATION HEREIN IS PRESENTED IN GOOD FAITH, BUT NO WARRANTY,EXPRESS OR IMPLIED, IS GIVEN NOR IS FREEDOM FROM ANY PATENT OWNED BYTHE DOW CHEMICAL COMPANY OR BY OTHERS TO BE INFERRED. IN THE HANDSOF QUALIFIED PERSONNEL, THE PROCEDURES ARE EXPECTED TO YIELDRESULTS OF SUFFICIENT ACCURACY FOR THEIR INTENDED PURPOSE; BUTRECIPIENTS ARE CAUTIONED TO CONFIRM THE RELIABILITY OF THEIRTECHNIQUES, EQUIPMENT, AND STANDARDS BY APPROPRIATE TESTS. ANYONEWISHING TO REPRODUCE OR PUBLISH THIS MATERIAL IN WHOLE OR IN PARTSHOULD REQUEST WRITTEN PERMISSION FROM THE DOW CHEMICAL COMPANY.

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