of ll of particular interest for the study of the structure of glass fiber are the investigations into the deformations ate fibers produced after the acid treatment of fiber of different composition The deformation was studied while the fiber was stretched on a gravimetric dynamometer with a reflec tor elongation reading. Apart from the instantaneous elastic deformation, measurements of the elastic lag were also made, i. e, the elongation of the fiber at different load times As is known, glass and glass fiber have a very high modulus of elasticity and a low elongation. Figure 2 shows the tension curve for aluminoborosilicate fiber which: is characteristic of commercial glasses. Its modulus of elasticity is about 200 kg/mmwhile its breaking strain is 1.50. The elastic lag at maximum load is only 1.7 of the elastic elongation. This deformation characteristic shows that the glass fiber possesses a high degree of stiffness and a low mo bility of its separate molecules. The slight deformation of glass fiber and especially its insignificant elastic lag are not characteristic of substances with a chain structure. Neither is a chain structure revealed through producing especially fine fibers from glass, when glass marbles are drawn out to a factor of tens of thousands. If sufficiently mobile chains had been present in the glass, an orientated structure should have been discernible when a fiber had been formed from it under the appropriate conditions, At the same time, numerous x-ray and microscopic examinations of silicate glass fibers have not disclosed any kind of orientation elements, or any substantial difference between the structures of glass Similar results were obtained in investigations into the most important properties of glass the elastic and plastic deformation, refractive coefficient, and Poisson's ratio chemical durability, electrical conductivity and other properties proved to be identical in glass of different dimensions. The only exceptions are certain mechan ical properties which are governed to a considerable degree by the scale factor. This is explained, not by the orientation of molecules in the fiber, but by the existence of faults which sharply reduce the strength of brittle substances. It is hard to imagine that molecular orientation which arises on drawing thin fibers from glass should have no effect whatever on their properties. Hence, the low deformation of glass fiber and the absence of an orientating effect do not confirm the existence of a chain structure in it. At the same time, the results of investigations conducted by V.v.Tara and his co-workers do show the existence of a chain structure in the silicate framework of a number of silicate glasses. Several other scientists are also of the same opinion, postulating that practical glasses consist of silicate chains and plane lattices of varying dimensions and ramifications. This contradiction is largely explained through the study of silicate fiber deformation. The deformation of silicate fiber produced by the acid treatment of fibers of different compositions is different from the de formation of glass-or quartz fiber, or glass. Its modulus of elasticity is only 1200-3000 kg/ mm2,.e,some 2.5-6 times lower than the modulus of elasticity of aluminoborosilicate fiber. The elastic lag in silicate fibers is many times higher than in glass fibers. It is more than 50 of the elastic elongation, and tens of times greater than the elastic lag in glass fibers(Fig. 2). By virtue of this the silicate fiber is more elastic than glass fiber The deformation of silicate fiber is directly related to the quantity of oxides driven off from the initial fiber. Its deformation steadily increases as the soluble constituents are removed from the fiber(Fig. 3). he high degree of deforma tion of the silicate fiber, and especially its elastic lag, are characteristic of a substance which has a chain structure. This confirms the postulation on the chain structure of the silicate framework. As has been shown earlier, however, such a structure of the silicate framework is not detected in prac tical glasses, and can only be observed after leaching soluble constituents out of them, In our opinion this is due to the fact that in practical glasses, the silicate framework is weighted by separate cations or whole struc tural groups which fill in its interstices and impede the movement of individual chains. As a result the struc ure of the glass becomes fairly rigid and the movement of individual molecules is impeded. But, as the sub stances which fill in the silicate framework are removed, and their cementing action is weakened, its chainOf particular Interest for the study of the structure of glass fiber are the investigations into the deformations of silicate fibers produced after the acid treatment of fiber of different compositions. The deformation was studied while the fiber was stretched on a gravimetric dynamometer with a reflec￾tor elongation reading. Apart from the instantaneous elastic deformation, measurements of the elastic lag were also made, i.e., the elongation of the fiber at different load times. As is known, glass and glass fiber have a very high modulus of elasticity and a low elongation. Figure 2 shows the tension curve for aluminoberosilicate fiber which: is characteristic of commerci~{i glasses. Its modulus of elasticity is about 200 kg/mm 2 while its breaking strain is 1.5%. The elastic lag at maximum load is only 1.7~o of the elastic elongation. This deformation characteristic shows that the glass fiber possesses a high degree of stiffness and a low mo￾bility of its separate molecules. The slight deformation of glass fiber and especially its insignificant elastic lag are not characteristic of substances with a chain structure. Neither is a chain structure revealed through producing especially fine fibers from glass, when glass marbles are drawn out to a factor of tens of thousands. If sufficiently mobile chains had been present in the glass, an orientated structure should have been discernible when a fiber had been formed from it under the appropriate conditions. At the same time, numerous x-ray and microscopic examinations of silicate glass fibers have not disclosed any kind of orientation elements, or any substantial difference between the structure s of glass and fiber. Similar results were obtained in investigations into the most important properties of glass:the elastic and plastic deformation, refractive coefficient, and Poisson's ratio chemical durability, electrical conductivity and other properties proved to be identical in glass of different dimensions. The only exceptions are certain mechan￾ical properties which are governed to a considerable degree by the scale factor. This is exp}ained, not by the orientation of molecules in the fiber, but by the existence of faults which sharply reduce the strength of brittle substances. It is hard to imagine that molecular orientation which arises on drawing thin fibers from glass should have no effect whatever on their properties. Hence, the low deformation of glass fiber and the absence of an orientating effect do not confirm the existence of a chain structure in it. At the same time, the results of investigations conducted by V. V. Tarasov and his co-workers do show the existence of a chain structure In the silicate framework of a number of silicate glasses. Several other scientists are also of the same opinion, postulating that practical glasses consist of silicate chains and plane lattices of varying dimensions and ramifications. This contradiction is largely explained through the study of silicate fiber deformation. The deformation of silicate fiber produced by the acid treatment of fibers of different compositions is different from the de￾formation of glass- or quartz fiber, or glass. Its modulus of elasticity is only 1200-3000 kg/mm ~, i.e., some 2.5-6 times lower than the modulus of elasticity of aluminoborosilicate fiber. The e}astic lag in silicate fibers is many times higher than in glass fibers. It is more than 50% of the elastic elongation, and tens of times greater than the elastic lag in glass fibers (Fig. 2). By virtue of this the silicate fiber is more elastic than glass fiber. The deformation of silicate fiber is directly related to the quantity of oxides driven off from the initial fiber. Its deformation steadily increases as the soluble constituents are removed from the fiber (Fig. 3). The high degree of deformation of the silicate fiber, and especially its elastic lag, are characteristic of a substance which has a chain structure. This confirms the postulation on the chain structure of the silicate framework. As has been shown earlier, however, such a structure of the silicate framework is not detected in prac￾tical glasses, and can only be observed after leaching soluble constituents out of them. In our opinion this is due to the fact that in practical glasses, the silicate framework is weighted by separate cations or whole struc￾tural groups which fill in its interstices and impede the movement of individual chains. As a result the struc￾ture of the glass becomes fairly rigid and the movement of individual molecules is Impeded. But, as the sub￾stances which fill in the silicate framework are removed, and their cementing action is weakened, its chain 610