Quantitative Determination of Sulfate Ion Instructions Page 1 of 3

OFI Testing Equipment – Quantitative Determination of Sulfate Ion Instructions Page 1 of 3

INSTRUCTIONS: QUANTITATIVE DETERMINATION OF SULFATE ION

EQUIPMENT:

QUANTITY DESCRIPTION PART NO.

1 Versenate Hardness Tit. Soln. (lml = 20 epm Ca & Mg) 205-12 1 Versenate Hardness Indicator Soln., 2 Fl. Oz. 205-02 1 Versenate Hardness Buffer Soln., 2 Fl. Oz. 205-04 1 Hydrochloric Acid N/50, 8 Fl. Oz. 275-04 1 10 ml pipette 153-40 1 Titration Dish Polyethylene 153-28 1 Standard Barium Chloride Soln., 16 Fl. Oz. 1 Standard Magnesium Chloride Soln., 8 Fl. Oz. 1 Instruction 145-20-I

OPTIONAL EQUIPMENT

1 Hot Plat, 115 Volt 168-01 1 Automatic Burette, Complete 153-10

This test involves the reaction of an excess amount of a standard barium chloride solution with sulfate Ion Precipitating Insoluble Barium Sulfate and then the titration of the excess Barium Chloride with Versenate Hardness titrating soln. Since versenate hardness titrating solution will react with any calcium or magnesium present in the sample, the total hardness of the sample must be determined first, followed by the precipitation of Barium Sulfate using the same volume of sample as was used to determine the total hardness, and then titration of the excess Barium Chloride Solution.

This test is very accurate for high concentrations of Sulfate Ion. It is not recommended for Sulfate Ion concentrations below 500 ppm or when the hardness of the sample is high 10,00 to 20,000 ppm because some accuracy is lost due to the high titrant.

OFI Testing Equipment – Quantitative Determination of Sulfate Ion Instructions Page 2 of 3

PROCEDURE:

I. DETERMINATION OF TOTAL HARDNESS OF SAMPLE

A. Add 50 mls of distilled water to a titration dish. Add 20 – 40 drops (2 – 4 mls) of hardness Buffer (Part No. 205-04) and 10 – 15 drops (0.5 – 0.75 mls) of Hardness Indicator Solution (Part No. 205-02). If a wine-red to a purple color develops, the distilled water contains Hardness, so add total hardness titrating soln. (Part No. 205-12) dropwise while stirring until the water turns to bright blue. B. Pipette 1 ml of sample into the titration dish and stir. A wine-red to a purple color will again develop if calcium and/or magnesium is present in the sample. C. Then add total hardness titrating solution, stirring continuously, until the sample again turns blue. D. The EPM Total Hardness of the sample = 20 x (mls of titrating solution used). Report this valve as THS in the Calculations formula for epm sulfate.

II. PRECIPITATION OF INSOLUBLE BARIUM SULFATE

A. Add 50 ml of distilled water to a titration dish, and lml of sample to be tested. B. Then add N/50 Hydrochloric Acid (Part No. 275-04) to adjust the pH of the diluted sample to 3 – 4. Check pH with pH meter or paper. C. (Optional) Bring the diluted sample to a boil and cool to dispel carbonates, bicarbonates and/or sulfides. D. Add 10 mls of standard barium chloride solution to the acidified sample and stir well. The precipitation of Barium sulfate will be observed. The sample should sit for 10 minutes at least with occasional stirring. (multiply 50 x the mls of Barium Chloride Solution used) and report this valve as BCU in the calculations formula for epm sulfate. E. (Optional) to speed up the precipitation of the sulfate, bring the diluted sample to a boil.

III. TITRATION OF EXCESS BARIUM CHLORIDE SOLUTION

A. After the precipitation of Barium Sulfate is complete add 20 – 40 drops of Hardness Buffer solution to adjust the pH of the sample to 10, check with pH meter or paper. Then add 10 –15 drops of Hardness Indicator Solution and lml (20 epm) of Standard magnesium chloride solution (the presence of Mg Ions enhances the end point color change) at this point the color of the sample should be wine-red or purple. B. Titrate with Versenate Hardness Titrating Solution until the sample turns blue 1. Record the mls of titrating solution used and multiply by 20. 2. Report this valve as TVTSU in the calculations formula for epm sulfate.

IV. CALCULATION FORMULAS

A. EPM Sulfate= (THS + BCU + 20) – (TVTSU) Ml of sample used OFI Testing Equipment – Quantitative Determination of Sulfate Ion Instructions Page 3 of 3

B. ppm sulfate = 48 x EPM Sulfate

WHERE:

THS = EPM of Total Hardness of Sample BCU = EPM of Barium Chloride Solution used 20 = EPM of Magnesium Chloride Solution used TVTSU = EPM of the total volume of titrating solution used

REMARKS:

I. If the valve for THS and TVTSU are nearly the same then insufficient Barium Chloride Solution was used and the test should be repeated using more Barium Chloride Solution. II. If the valve for TVTSU exceeds the valve for THS by more than 200 epm the test should be rerun sing LESS Barium Chloride Solution. III. Barium Chloride is extremely poisonous and extreme care should be used when transferring with a pipette. As an added precaution and automatic Burette is recommended for this practice.