悬浮物、氯化物、硬度

时间安排 预习时，首先洗净 SS 测定需用的称量瓶，将 滤膜置入，烘第一遍；再清洗其他玻璃器皿。 预习，绘制数据表格，考虑注意事项。 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 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.

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.

What is sample pretreatment? Separation methods: Filtrationultra-filtration Extraction Centrifugation Osmosis Chromatography Electrophoresis

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

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

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

Procedure of titration 1.Filling titrant solution, adjusting zero mark. 2.Put XX mL sample solution into a flask 3.Add a few drops of indicator solution 4.Titrate with titrant solution until the endpoint 5.Record the volume of titrant consumed 6.calculation

precipitation titration Ag + + Cl - AgCl white, pKsp=9.74 2Ag + + CrO 4 2- Ag 2 CrO 4 reddish, pKsp=11.92 Ag 2 CrO 4 ppt (more soluble) form after AgCl (less soluble) Suitable pH range: 6.5 ～ blank and 2 samples for each student Note: V blank ≒ V sample Color turning: light yellow green to reddish

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

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

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(HCO 3 ) 2 CaCO 3 ＋ CO 2 ＋ H 2 O Mg(HCO 3 ) 2 MgCO 3 ＋ CO 2 ＋ H 2 O

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

complexation titration 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 3.At the endpoint Ca/Mg-EDTA, colorless Free EBT, light blue

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