4 STUDIES IN GELS lOI 



silicic acid, lignin, etc. are embedded in the amorphous state and there- 

 fore do not produce X-ray interferences. For this reason the amount 

 of space occupied by the intermicellar regions in frameworks was 

 totally unknown. To obtain information in this important field, 

 foreign substances must be introduced into these spaces, where they 

 crystallize and can then be submitted to X-ray analysis (Frey-Wyss- 

 LiNG, 1937a). We must therefore create by artificial means an inter- 

 micellar substance possessing lattice order, which enables us to derive 

 quantitative data of the dimensions of the unknown submicroscopic 

 regions. Gold and silver crystals have proved to be the most suitable 

 for this purpose. Following Ambronn, the objects are soaked in 

 1-2",', solutions of gold chloride or silver nitrate, then carefully dried 

 with blotting paper and finally the salt absorbed is reduced by means 

 of light or hydrazin hydrate (Frey, 1925). In this way microscopically 

 homogeneous colourings are obtained displaying a beautiful di- 

 chroism (compare Ambronn and Frey, 1926, coloured table; Wiener 

 1926a). The X-ray diagram of the dyed fibres shows Debye-Scherrer 

 rings of crystalline silver or gold (Fig. 69) in addition to the fibre 

 diagram of the framework substance (ramie fibre, silk and wool). The 

 annular interferences prove that the metal crystallites imbedded take 

 up all possible positions with respect to the fibre axis. The size of the 

 cubic gold and silver crystals is calculated from the breadth at half- 

 maximum of the interference rings (Fig. 70). 



The investigation produced the surprising evidence that metal 

 crystallites with a cross-section of about 50 A are incrusted in silk 

 and wool, and particles even exceeding a diameter of 100 A in ramie 

 fibres (Table XII). Since the strands of the micellar framework in ramie 

 fibres have a thickness of only 50 A, the artificially embedded metal 

 crystallites occupy an unexpectedly large space. Notwithstanding their 

 great strength, cellulose fibres must, therefore, be built rather loosely, 

 a fact which was already known from density measurements in the 

 bleached fibres used in these experiments. After removal of all foreign 

 substances, the density of ramie fibres amounts to only 1.39, whereas 

 the density of cellulose is 1.59. There should therefore be about 12.6% 

 of submicroscopic empty space* (Frey-Wyssling and Speich,i942). 



^ The density 1.39 ~ 0.03 is derived from accurate determinations of mass and volume. 

 If, instead of the density of crystalline cellulose, one uses the density 1.55 of the incom- 

 pletely crystallized fibre measured in toluene, one finds a discrepancy of 10.3% . 



