Abstract
About 1-2g of an air dried artificial silk made by viscose process in Japan were immersed in the caustic soda solution of various concentrations at various temperatures for 4 hours. and the solubility was determined by estimating the soluble portion obtained as a filtrate by oxidation with potassium bichromate. The oxidation was carried out by the method of Bray and Andrews with some modifications.
The solubility is greater as the temperature is lower, and as far as this experiment concerns the temperature of 0°C gives a maximum solubility. The solubility is greatly affected by the concentration of alkali solution, and it reaches a maximum as the concentration it about 9% NaOH by weight. Under these optimum conditions the solubility of a viscose silk of an ordinary quality was 92.9%.
The greater solubility of artificial silk in alkali solution is supposed to be effected by the low degree of the orientation of the unit cell or micell of cellulose. According to the X-ray research, worked out by K. Atsuki and M. Ishiwara, the details of which will be published in later, the unit cells as well as the micelles are smaller, more distorted and less oriented in viscose silk than in natural fibers such as hemp, ramie or cotton. In an ordinary viscose silk the arrangement of the micelles is only regular in the direction of the fiber axis, and random in the other two directions. A numbers of the hydroxyl groups of the glucose chains are not in attraction or saturation with each others, and therefore the valence force between micelles is weak, and the hydroxyl groups or micelles adsorbs the alkali solution easily to a greater amount, resulting in the gelatinization as well as dispersion of micelles. It may be considered that the greater solubility of the artificial silk in alkali solution suggests that the structure of the fiber is less oriented, and the tensile strength of the fiber in dry and wet state is also less.
