The effects of condensed sodium phosphates, sodium metasilicate and soap on the degumming of _??_aw silk were investigated.
As condensation salts, sodium pyrophosphate, sodium triphosphate and sodium metaphosphate glass were used.
The pH values, the permeating rate and the sericin dissolving power of phosphates, silicate and soap were measured at the same concentration and temperature respectively.
The results showed that the pH values of phosphates were lower than those of silicate and soap, the permeating rate of phosphates was greater than that of soap and smaller than that of silicate, and the dissolving power of silicate was the greatest and that of soap the smallest.
Below 70°, the solutions of phosphates and soap showed little or no dissolving power for sericin, but the solution of silicate dissolved sericin considerably.
Treated by soap below 70°, the weight of silk was increased by the contaminations of free fatty acid or metallic soap.
The functions which affect the dissolving power for sericin are considered to be pH values and permeating rate of the degumming reagents; but further investigations have to be made to make clear the mechanism of the reaction between phosphates and sericin, (These are to be reported later.)
To conclude, risks are seen in either case (1) of dissolving a part of fibroin when treated with metasilicate solutions or (2) of contamination by fatty acid or metallic soap when treated with soap solution. The condensed phosphates, therefore, are considered to be better degumming reagents for silk.