The sponge was cut
into pieces of approximately 2.0-2.5x1.5-1.7 cm., 2-3 mm. thick, soaked in boiling water for 30 min,
thoroughly washed under tap water, and left for 24 h in distilled water, changed 3-4 times. The sponge
discs were oven dried at 70oC and stored in desiccators till their further use (Fig. 1).