In the field of filature, it is valuable to know the solubility of sericin in the cocoon produced by Bombyx mori for judging its reelability.
Concerning the cocoons soaked by hot water, the authors investigated the solubility of sericin by Folin's colorimetry and the swelling of cocoon shells, and discussed the relation between them.
The results are obtained as follows:
1. Although about 5% errors exist between the values of colorimetry and Kjeldahl method, the same experimental trends are observed between them.
2. The swelling of cocoon shells are closely concerned to the solubility of sericin, that is, a lot of cocoons showing the lower swelling has a small solubility of sericin.
3. Heat drying has a great influence on the swelling and solubility of the cocoon shells, and the high temperature produces a bad effect to them.
4. Thickness and each layers of the cocoon shell affect on its swelling and sericin solubility. It is considered that the differences of swelling or solubility between the silk layers of the cocoon chiefly depend upon the chemical properties of sericin, and the differences with thickness chiefly depend upon the physical structure of the cocoon shells.