Determination of the Molecular Weights of Colloids

Abstract

IN the January issue of the Berichte der deutschen chemischen Gesellschaft˜Prof. H. Staudinger discusses the validity of the method of deducing the molecular weight of a colloid of high molecular complexity from observations of its specific viscosity. The author claims that this new method is applicable to the investigation of numerous complex naturally occurring substances such as cellulose and india-rubber, since many physical properties such as elasticity, ductility, solubility, etc., are functions of the length of the molecular chain. Older methods of determining molecular weights of complex molecules are more restricted in their application. Thus the cryoscopic methods give very low results in dilute solutions and in more concentrated solutions the relation between molecular weight and osmotic pressure is no longer simple. The diffusion method is only suitable for particles of spherical shape and can therefore not be applied to the long fibre-molecules of many natural colloids.