The Effect of Regain on the Rate of Adsorption of Stannic Chloride by Silk Fibroin

Abstract

The effect of the moisture content of silk fibroin on the amount of weighting it takes up in given periods of time from a 30° Bé. stannic chloride solution has been determined. Saturated silk (> 35% moisture content) attains maximum adsorption much faster than does dry silk, whereas a minimum rate of adsorption exists for silk of about 10–23% moisture content. An explanation has been advanced for these phenomena based on the rate of swelling of silk in water and in stannic chloride solution, the size of the pores in dry silk and the effect that the water in these pores would have on the stannic chloride solution entering them. It is pointed out that the weighting taken up by silk from stannic chloride solutions is probably adsorbed not as stannic chloride but as a mixture of the various tin complexes which have been shown to exist in aqueous stannic chloride solutions. The effect on the weighting of increasing the temperature of the hydrolyzing bath and of the addition of inorganic chlorides and sulphates to this bath has also been investigated. The final weighting retained by the silk has been shown to consist of hydrated stannic oxide, the amount of water present depending upon the conditions obtaining during hydrolysis and drying.