# Water Soluble Matter

### APPARATUS:-

• Evaporating dish- 50

• Muffle furnace – 800 ± 25°C
• Desiccator

• Mechanical shaker
• Oven  - 102 ± 2°C
• Round bottom flask- 250 ml

• Whatman filter paper No. 1

### PROCEDURE:-

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

Determination
• 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.

CALCULATION:-
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.

Permissible Error - The results of a duplicate determination shall not differ from one another by more than 0.2 percent calculated on the original weight of the material taken for the test.

REFERENCE: - IS 582: 1970 LC 6- Method for determination of water soluble matter in leather materials.