Water Soluble Matter
- Evaporating dish- 50
- Muffle furnace – 800 ± 25°C
- Mechanical shaker
- Oven – 102 ± 2°C
- Round bottom flask- 250 ml
- Whatman filter paper No. 1
- Distilled water.
- Sulphuric acid – 2N.
Preparation of evaporating dish:-
- Heat the evaporating dish at 800±25°C in muffle furnace for half an hour.
- Remove the dish and cool in Desiccator.
- Weigh quickly and note the dry weight of dish
- Cut out at least two specimens each weighing about 10 gm.
- Remove the grease from the leather sample by solvent extraction procedure in a Soxhlet apparatus for 20 cycles.
- Free the extracted leather from solvent by spreading out on a clean surface and leaving it exposed to air.
- Transfer the grease free leather to the 1000 ml flask.
- Add 500 ml of water and shake in a mechanical shaker at room temperature for 2 hours.
- After two hours, separate the liquid from leather by filtration using Whatman filter paper No. 1.
- Pipette out 50 ml of the filtrate using 50 ml one mark pipette and reject the filtrate.
- Again pipette out 50 ml of filtrate and pour in previously heated, cooled and tarred evaporating dish.
- Evaporate the filtrate to dryness in a water bath.
- After evaporation, shift the evaporating dish into a hot air oven and dry the residue at 102 ± 2°C for two hours.
- Cool the dish in a Desiccator and weigh quickly.
- Repeat the process of drying in oven till the weight change between two successive weighing is less than 0.002 gm.
Note: – If the quantity of water soluble mineral substances is likely to be less than 1.0 percent of the leather weight, the determination should be made on 100 or 200-ml aliquot.
Calculate the total water soluble matter as follows;-
Water soluble matter, percent = W x 100
Where, w = weight in gm of dry residue left after drying.