METHOD 9253 CHLORIDE (TITRIMETRIC, SILVER NITRATE)

1 CD-ROM9253 - 1 Revision 0 September 1994 METHOD 9253 CHLORIDE (TITRIMETRIC, SILVER nitrate ) AND METHOD is intended primarily for oxygen bomb combustates orother waters where the CHLORIDE content is 5 mg/L or more and where interferencessuch as color or high concentrations of heavy metal ions render METHOD OF adjusted to pH is titrated with SILVER nitrate solutionin the presence of potassium chromate indicator. The end point is indicated bypersistence of the orange- SILVER chromate , iodide, and sulfide are titrated along with the and polyphosphate interfere if present in concentrations greaterthan 250 and 25 mg/L, respectively. Sulfite and objectionable color or turbiditymust be eliminated. Compounds that precipitate at pH (certain hydroxides)may cause error by sodium carbonate from the bomb combustion may react withsilver nitrate to produce the precipitate, SILVER carbonate.

2 This competitivereaction may interfere with the visual detection of the end point. To removecarbonate from the test solution, add small quantities of sulfuric acid followedby AND laboratory titrimetric equipment, including 1 mL or 5 mLmicroburet with mL gradations, and 25 mL balance: capable of weighing to A volumetric flask: 1 grade chemicals shall be used in all tests. Unlessotherwise indicated, it is intended that all reagents shall conform to thespecifications of the Committee on Analytical Reagents of the American ChemicalSociety, where such specifications are available. Other grades may be used,provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the water. All references to water in this METHOD refer toreagent water, as defined in Chapter peroxide (30%), - 2 Revision 0 September indicator solution (10 g/L).

3 Chromate indicator solution. Dissolve 50 g of potassiumchromate (KCr0) in 100 mL of reagent water and add SILVER nitrate (AgN0) until243a slightly red precipitate is produced. Allow the solution to stand, protectedfrom light, for at least 24 hours after the addition of AgN0. Then filter the3solution to remove the precipitate and dilute to 1 L with reagent nitrate solution, standard ( ). Crush approximately5 g of SILVER nitrate (AgN0) crystals and dry to constant weight at + g of the crushed, dried crystals in reagent water anddilute to 1 L with reagent water. Standardize against the standard NaClsolution, using the procedure given in Section CHLORIDE solution, standard ( ). Dissolve g + g of sodium CHLORIDE (dried at 600EC for 1 hr) in CHLORIDE -free waterin a 1 liter Class A volumetric flask and dilute to the mark with reagent hydroxide solution ( ).

4 Dissolve approximately 10 g ofNaOH in reagent water and dilute to 1 L with reagent acid (1:19), HS0. Carefully add 1 volume of concentrated24sulfuric acid to 19 volumes of reagent water, while COLLECTION, PRESERVATION, AND samples must have been collected using a sampling plan thataddresses the considerations discussed in Chapter Nine of this are no special requirements for 50 mL or less of the sample, containing between mg and20 mg of CHLORIDE ion, into a white porcelain container. Dilute to approximately50 mL with reagent water, if necessary. Adjust the pH to the phenolphthalein endpoint (pH ) using HS0 (Sec. ) or NaOH solution (Sec. ). approximately mL of KCr0 indicator solution and mix. Add24standard AgN0 solution dropwise from a 25 mL buret until the orange color3persists throughout the sample when illuminated with a yellow light or viewedwith yellow goggles.

5 Be consistent with endpoint the procedure described in Secs. and using exactlyone-half as much original sample, diluted to 50 mL with halide-free sulfite ion is present, add mL of H0 to the samples22described in Secs. and and mix for 1 minute. Adjust the pH, then proceedas described in Secs. and - 3 Revision 0 September the CHLORIDE ion concentration in the originalsample, in milligrams per liter, as follows: CHLORIDE (mg/L) = [(V - V) x N x 71,000] / S12where:V =Milliliters of standard AgN0 solution added in titrating13the sample prepared in Sec. =Milliliters of standard AgN0 solution added in titrating23the sample prepared in Sec. =Normality of standard AgN0 solution. 3S =Milliliters of original sample in the 50 mL test sample prepared in Sec. 71,000 =2 x 35,500 mg Cl/equivalent, since V - quality control data should be maintained and available foreasy reference or inspection.

6 Refer to Chapter One for specific quality a standard reference material to ensure that correctprocedures are being followed and that all standard reagents have been preparedproperly. a minimum of one blank per analytical batch or twentysamples, whichever is more frequent, to determine if contamination has one matrix spike and matrix duplicate every analytical batchor twenty samples, whichever is more frequent. Matrix spikes and duplicates arebrought through the whole sample preparation and analytical data are based on 32 data points obtained by fivelaboratories who each analyzed four used crankcase oils and three fuel oil blendswith crankcase in duplicate. The samples were combusted using METHOD 5050. Adata point represents one duplicate analysis of a sample. Three data points werejudged to be outliers and were not included in these The precision of the METHOD as determined bythe statistical examination of inter-laboratory test results is asfollows:Repeatability' (Reproducibility' (CD-ROM9253 - 4 Revision 0 September 1994 Repeatability - The difference between successive results obtainedby the same operator with the same apparatus under constant operatingconditions on identical test material would exceed, in the long run, inthe normal and correct operation of the test METHOD , the following valuesonly in 1 case in 20 (see Table 1).))

7 *where x is the average of two results in - The difference between two single and independentresults obtained by different operators working in different laboratorieson identical test material would exceed, in the long run, the followingvalues only in 1 case in 20:where x is the average of two results in g/g.* The bias of this METHOD varies with concentration,as shown in Table 2:Bias = Amount found - Amount , ; et al. Reagent Chemicals, American Chemical SocietySpecifications, 7th ed.; American Chemical Society: Washington, DC, Annual Book of ASTM Standards, Vol. ; "Standard Specification forReagent Water"; ASTM: Philadelphia, PA, 1985; , A.; Estes, E. D.; Hardison, D. L.; and Myers, L. E. "Validationof Methods for Determining Chlorine in Used Oils and Oil Fuels," Prepared Environmental Protection Agency, Office of Solid Waste.

8 EPA Contract , WA 80. July - 5 Revision 0 September 1994 TABLE AND REPRODUCIBILITY FOR CHLORINE IN USEDOILS BY BOMB OXIDATION AND SILVER nitrate TITRATION Average value Repeatability Reproducibility ( g/g) ( g/g) ( g/g) 5001803551,0003607101,5005401,0652,00072 01,4202,5009001,7753,0001,0802,130 TABLE AND BIAS DATA FOR CHLORINE IN USED OILS BYBOMB OXIDATION AND SILVER nitrate TITRATION Amount Amountexpected found Bias, Percent( g/g) ( g/g)

9 ( g/g) bias 320645325+102480665185+39920855-65-71,49 81,51517+11,5271,369-158-103,0292,570-46 0-153,0452,683-362-12 CD-ROM9253 - 6 Revision 0 September 1994 METHOD 9253 CHLORIDE (TITRIMETRIC, SILVER nitrate )