9.2 - Determination of Total Suspended and Total Dissolved Solids in p.p.m. (Leaving Cert Chemistry): Revision Notes
9.2 - Determination of Total Suspended and Total Dissolved Solids in p.p.m.
Experiment Summary
This experiment involves determining the concentrations of total suspended solids (TSS) and total dissolved solids (TDS) in a water sample.
Suspended solids consist of particulate matter that does not dissolve, while dissolved solids include ions and small molecules dissolved in the water. The TSS is determined by filtration, and the TDS is measured by evaporating the filtered water and recording the remaining solid mass.
Materials and Apparatus Required
Chemicals
- Water sample (e.g., river or lake water)
- Anhydrous sodium carbonate (for TDS test)
Apparatus
- Philtre paper (small-pore)
- Retort stand and clamp
- Philtre funnel
- Beakers (250 cm³ and 1000 cm³)
- Drying oven
- Balance (precision to 0.01 g)
- Graduated cylinder (100 cm³)
- Evaporating dish
- Bunsen burner or hot plate
Safety Precautions
- Wear safety glasses throughout the experiment.
- Avoid contact with potentially toxic or polluted water samples.
- Handle hot equipment (oven, hot plate) with care to avoid burns.
Method
Determination of Total Suspended Solids (TSS)
- Weigh the philtre paper: Record the mass of a clean, dry piece of philtre paper using a balance.
- Filter the water sample: Pass 1 litre of the water sample through the philtre paper set in a funnel.
- Dry the philtre paper: Place the philtre paper in an oven set at approximately 105°C and allow it to dry overnight.
- Weigh the dried philtre paper: After drying, weigh the philtre paper again and calculate the increase in mass.
- Calculate the TSS: The mass of the suspended solids in the water is the difference in the mass of the philtre paper before and after filtration.
- The TSS concentration is calculated as mg/l (ppm).
Determination of Total Dissolved Solids (TDS)
- Weigh the evaporating dish: Record the mass of a clean, dry evaporating dish.
- Add the filtered water: Transfer 100 cm³ of the filtered water from the previous experiment into the dish.
- Evaporate the water: Place the dish on a hot plate or in an oven set at 105°C until all water has evaporated and the solids remain.
- Weigh the dish: After cooling, weigh the dish again to determine the mass of the dissolved solids.
- Calculate the TDS: The difference in mass between the empty dish and the dish with dissolved solids gives the TDS in mg/l (ppm).
Results
Table of Results for Total Suspended Solids
| Measurement | Value |
|---|---|
| Mass of dry philtre paper before use | 1.42 g |
| Mass of dried philtre paper after use | 1.60 g |
| Mass of suspended solids | 0.18 g |
| Volume of water sample | 1 litre |
| Total suspended solids (TSS) | 180 ppm |
Table of Results for Total Dissolved Solids
| Measurement | Value |
|---|---|
| Mass of clean evaporating dish | 99.05 g |
| Mass of dish after evaporation | 100.54 g |
| Mass of dissolved solids | 1.49 g |
| Volume of water sample | 100 cm³ |
| Total dissolved solids (TDS) | 14,900 ppm |
Example Questions with Answers
Q1: What causes high levels of total suspended solids in water samples?
High TSS levels can result from algal growth, sewage discharges, sandpit washings, and other sources of pollution.
Q2: Why must the water be filtered before determining the total dissolved solids?
Filtering removes suspended solids, ensuring that only dissolved substances remain in the water for accurate measurement of TDS.
Q3: What impact do high TSS levels have on the environment?
High TSS levels reduce light penetration, interfering with plant life and damaging aquatic organisms. They can also indicate the presence of harmful pollutants.
Q4: How are suspended particles typically removed from water in treatment plants?
Suspended solids are removed by settling in tanks and filtration through sand and gravel layers in water treatment plants.
Q5: How are dissolved solids removed during water purification?
Dissolved solids are typically removed through processes like reverse osmosis, distillation, or ion exchange during water purification.