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r � ri o-` 3 ' CHLORIDE APPENDIX Lb .-, Mohr Argentometric Method* Page I of 2 For ftter,Wastewater and Sea Water llub-cdtsc4lon This snmlysis includes procedures for the Buret Method and the digital Titrator Method. Chlorides are present in all potable water supplies and in sewage,usually as a metallic salt.When sodium is present in drinking water,chloride concentrations in excess of 250 ntg/L give a salty taste.If the chloride is present as a calcium or magnesium salt,the taste detection level may be as high as 1000 mg/L chloride. Chloride is essential in the diet and passes through the digestive syw4em unchanged to become one of the major components of raw sewage. The wide use of zeolite in water softeners also contributes a large amount of chloride to sewage and wastewaters. High chloride concentrations in water are not known to have toxic effects on man,though large amounts may act corrosively on metal pipes and be harmful to plant life.The masimurn allowable chloride concentration of 250 mg/L in drinking water has been established for reasons of taste rather than as a saleguard against physical hazard. The Mohr Argentametric Method,the most widely Known test for chloride,uses a chromate indicator.The sample is titrated with a silver nitrate standard solution to selectively precipitate first the chloride present,then the chromate.The end point of the titration is indicated by the first appearance of the ted silver chromate pre- cipitate. The newer Mercuric Nitrate Method has become popular due to the sharp yellow to pinkish-purple end point of diphenylcarbazone and the absence of a precipitate during the titration.A single,stable powder has beende- veloped combining the color indicator with an appropriate buffer to establish the correct sample pH.Inteder- J ences are discussed in the procedural notes for each test method. A Sodium Chloride Standard Solution, 1000 mg/L as Cl,is available from Hach for checking the accuracy of the test. A procedure detailing the use of the Voluette*Analytical Standards System of standard additions is given in the final note ofeach titration method. WARNING Some of the chemicals used in this procedure may be hazardous to the health and safety ofthe k user ifinappropriately handled oraccidentally misused.Please read all wamings on the reagent labels and read thn safetysection ofthis manual.Ifyou have questions or would like a reprint of the safely section.please contact Hach.In the procedure,hazardous substances appear in italic _ typeface wherever they am used in the test a;:i deserve extra care in handling.It is alwaysgood Practice to wear safetyglasses when handling chemicals. Wash thoroughly if co act occur. Follow instructions cttlofully. A' Sampling and Storage E Collect samples in clean plastic or glass bottles.Samples can be stored at room temperature for a least seven days. pH Adjustment E Highly alkaline samples should be adjusted to a pH of approximately 2.5 with S..S.N Sulfuric Aciu Standard Solution before testing.Highly acidic samples should be adjusted to approximately pH 2.5 with 5.0 NSodium h Hydroxide Standard Solution. Do not use is pH electrode in the sample container as this will introduce chloride -- contamination.Pour offa small portion in a separate container to measure the pH Where a significant umnuht — ems,! of acid orbase has been used,a volume correction should be made by dividing the total volume(sample+acid r or base)by the sample volume and multiplying the result times the final test reading. - ��..'. •AJ.ped town Srwaln7llkYh•hlr rA•tr�rrnrvr.in..1 N'+hY anJ Rnnx shr �