Occurrence of Thin Membranes in the Structure of Wool

Abstract

WOOL keratin is considered to be completely soluble in sodium sulphide. 30 ml. of 0·3 M sodium sulphide was added to 1 gm. carefully purified, wool, and this mixture was allowed to stand for about a month. After this time a light green solution was obtained, but the solution showed a slight opalescence. The particles causing this opalescence (estimated to be not more than 0·1 per cent of the Wool) could be separated from the solution by centrifuging. After separating and washing with water, the solid matter was examined under the electron microscope. The specimen was mounted on collodion and observed directly. The solids proved to consist mainly of thin membranes, mostly rolled or folded, as is seen in Fig. 1. In order to determine the thickness of the membrane itself a collodion replica was made and gold-shadowed at a declination of 1 : 10. Fig. 2. shows how the thin membranes are rolled and the rolls flattened, probably by the surface tension during the drying. From the length of the shadows the thickness is calculated to be something between 50 and 100 A. Fig. 3. is a shadow-cast replica, where part of the wool membrane has stuck to the collodion. In part it shows both the membrane and the corresponding impression and is in that way interesting purely from the electron-micrograph point of view.