Determination of Water Soluble Matter – Leather Materials

  • Evaporating dish- 50
Evaporating dish

  • Muffle furnace – 800 ± 25°C
  • Desiccator

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

  • Whatman filter paper No. 1



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.

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.

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