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悬浮物、氯化物、硬度

悬浮物、氯化物、硬度. 时间安排. 预习时，洗净玻璃器皿，将滤膜置入，烘第一遍。 上课前，采集“若谷”学区前的湖水样品，每人装满 1 个矿泉水瓶，上课时带来。 上午上课时，先集中听讲解“称量”，然后分成小组称滤膜，或准备滴定。 集中听讲解 3 个实验。 分头做实验。. 2.4. Determination of Suspended Solids.

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悬浮物、氯化物、硬度

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  1. 悬浮物、氯化物、硬度

  2. 时间安排 • 预习时，洗净玻璃器皿，将滤膜置入，烘第一遍。 • 上课前，采集“若谷”学区前的湖水样品，每人装满1个矿泉水瓶，上课时带来。 • 上午上课时，先集中听讲解“称量”，然后分成小组称滤膜，或准备滴定。 • 集中听讲解3个实验。 • 分头做实验。

  3. 2.4. Determination of Suspended Solids • Purpose: To understand the principles of weighing method, and one of the sample pretreatment methods, filtration, as well as to master the methods of measurement of suspended solid.

  4. Questions What is SS? • Definition: remained on 0.45 µm membrane What is weighing method? • Weight difference How to hold the weighing bottle? • Do not direct touch it.

  5. What is sample pretreatment? Separation methods: • Filtration ultra-filtration • Extraction • Centrifugation • Osmosis • Chromatography • Electrophoresis

  6. Key points • To get the constant weight • Enough dry time • Enough cooling time • Desiccator • Desiccant--- Si gel

  7. 2.5. Determination of Chloride • Purpose: To understand the principle of chloride measurement, and to master one of the volumetric methods, precipitation titration.

  8. What is titration? • One of the volumetric methods, reaction of titrant and target analyte. Type of titration: Acid-base Redox (reducing-oxidizing) Complexation precipitation

  9. Procedure of titration • Filling titrant solution, adjusting zero mark. • Put XX mL sample solution into a flask • Add a few drops of indicator solution • Titrate with titrant solution until the endpoint • Record the volume of titrant consumed • calculation

  10. precipitation titration Ag+ + Cl- AgCl white, pKsp=9.74 2Ag+ + CrO42- Ag2CrO4 reddish, pKsp=11.92 Ag2CrO4ppt (more soluble) form after AgCl (less soluble) Suitable pH range: 6.5～10.5 1 blank and 2 samples for each student Note: Vblank ≒Vsample Color turning: light yellow green to reddish

  11. samples • Diluted seawater samples • Tap water • Titrate the blank first, for comparing the color.

  12. 2.6. Determination of Total Hardness • Purpose: To understand the principle of hardness measurement, and to master one of the volumetric methods, complexation titration.

  13. What is hardness? • Total hardness is the total concentration of Ca and Mg in water, which includes carbonate hardness and non-carbonate hardness. What is temporary hardness? • Carbonate hardness is equal to the amount of Ca and Mg carbonate or bicarbonate Ca(HCO3)2 CaCO3 ＋CO2 ＋H2O Mg(HCO3)2 MgCO3 ＋CO2 ＋H2O

  14. What is hardness? What is permanent hardness? • non-carbonate hardness contains chloride, sulfate, or nitrate • cannot be removed by boiling

  15. complexationtitration 1. EBT, a blue indicator Ca/Mg + EBT, form purple-red complex 2. Titrate with EDTA Ca/Mg-EBT, less stable Ca/Mg-EDTA, more stable • At the endpoint Ca/Mg-EDTA, colorless Free EBT, light blue

  16. samples 3 samples for each student • Tap water • Drinking water • Lake water Note: If the sample volume is double, add double buffer

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