Action of alkaline copper-solution on silk fibroin II

Abstract

From the results of our researches on the phenomena seen in the dissolution of fibroin in copper-amine solutions and also on their chemical reactions, especially in the case of dissolving a large quantity of fibroin in a solution of a given copper content, the following conclusions were obtained. (1) The dissolution phenomena of fibroin in this case are very abnormal and are comparable to a similar case usually observed in the dissolution of colloidal substances, in which the solubility is greatly affected by the amounts of the substances used. (2) The maximum degree of solubility of fibroin in copper-amine solutions with a given copper content was determined under definite dissolving conditions. Expressing these relations in terms of their chemical equivalents i.e. Fibroin: Cu=227: 63.6, which had been ascertained by the author in his previous study, the following equation can be derived: Max. degree of solubility of fibroin/Copper content of the solution = 1 (3) From the dissolution of fibroin in a copper oxide-ethylendiamine solution in which the ratio of fibroin to copper is equal to that shown in (2), a complex fibroin-copper-ethylendiamine compound was isolated with the following composition : Fibroin : Cu : en = 1 : 1 : 1 where, en = ethylendiamine. It was ascertained that the relations of the smallest amounts of copper and amine necessary to dissolve the given amounts of fibroin can be also expressed by these ratios. (4) The abnormal phenomena connected with the dissolution of fibroin in copper-amine solutions, are chiefly attributable to the nature of the distribution of copper and amine to fibroin and also to the combining ratios between these three components that occur when fibroin is added in large excess and there are definite chemical reactions between fibroin, copper and amine not only in the solution, but also in the solid phase.