Methodology of Total Solids

CHAPTER 2

DESIGN AND METHODOLOGY

Total Solids Dried 103-105 ℃

The Wednesday class assigned to heat the clean evaporating dish or the crucible at 103 to 105 ℃ for one hour. They let it store and cool the dish in the desiccator until it is needed. Then they weighed the dish immediately and this weight is the basis for the weight of the total solids.

So after the constant weighing of the evaporating dish, we measured 25 ml of sample water and then pipet the measure volume of well-mixed sample, during mixing, to a preweighed dish. While for a homogeneous samples, pipet it from the approximate midpoint of the container but not in the cortex. Choose a point both middepth and midway between wall and vortex. Also while transferring the samples, be sure that the crucible is not contaminated by your hands and others. So we used a tong for the holding the crucible. Then stir the sample with a magnetic stirrer during the transfer. If necessary, add successive sample portions to the same dish after evaporation. When evaporating in a drying oven, lower the temperature to approximately 2 ℃ below boiling in order to prevent splattering. We dried the evaporated sample for at least one hour in an oven at 103 to 105 ℃. In drying process, be alert in watching the crucible, it must be follow the given time and temperature so that it may not burnt or lead to inaccurate datas. After one hour, we cooled the dried crucible in desiccator to necessary balance temperature and we weighed the crucible. The Wednesday, Friday and as well as the Saturday class repeated the cycle of drying, cooling, desiccating and weighing until the constant weight is obtained, or until the weight changed is reached less than 4% of previous weight or 0.5 mg or whichever is less. Each group of the assigned class will do the constat weighing everyday. Another notice is that when weighing dried sample, be alert to change in weight because of the air exposure and/or sample degradation. Then analyze again at least 10% of all samples in duplicate because duplicate determination should agree within 5% of their average weight.

Total Dissolved Solids Dried at 180 ℃

Before filtering the sample water, we prepared first the evaporating dish or the crucible. If the volatile solids are to be measureed, ignite cleaned evaporating dish for 2 hour on its first trial in a muffle furnace. If only total dissoved solids are to be measured, heat the clean dish to 180 ℃ for one hour in an oven.

So we measured 25 ml of sample water and filtered it into Buchner funnel. We settle first the filter paper in the appropriate place so that the sample will not spill out. Then insert the disk with wrinkled side up into filtration apparatus to hold the filter paper. We opened the vacuum and poured the sample to Buchner funnel passing through the filter paper. We waited until the there’s nothing water would drop. After the filtration process, we transferred the total filtrate and its washing into the weighed crucible and set aside the filter paper into the watch glass and evaporate it to dryness on drying oven. If necessary, add successive portions to the same dish after evaporation. We dried the evaporated sample for at least one hour in an oven at 180 ℃ and then cooled it in a desiccator to a balance temperature. When the temperature is settled, we weighed the crucible immediately. The same as the total solids, we repeated the process; starting from drying, cooling, desiccating and weighing until a constant weight is obtained or until weight change is less than 4% of previous weight or 0.5 mg, whichever is less. It analyzes the same as the total solids. The crucible in total dissolved solids is labeled as B while the total solids labeled as A.

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