capacity of the silicate fiber is sharply reduced after this. On heating the acid treated fiber from 200@C or over, although it retains its porous structure, its adsorption capacity is again very low. Porous silicate fiber produced from sodium silicate retains its form and has a very high strength reach Ing 100 kg/mm From this it follows that the basis of glasses from the composition under consideration is a very strong silicate framework consisting of continuously interlinked Sio4 tetrahedra On reaching fibers of a ternary composition which contains up to 12)o tertiary oxides, besides Na2O, with acid, alkali are also driven off from them, but nearly all the tertiary oxides remain in the fiber together with the silica(Fig. 1). The thermostability of these fibers, at a sufficient leaching time in accordance with the structural diagram, is somewhat lower than in quartz fiber. The tertiary oxides CaO, Zno, Bao, PbO, B2O3, TiOz, etc., are fairly firmly bonded in the basic frame work when they are contained in the glass in a small quantity. be assumed that a nunber of oxides (Al2 O3, B2O3, Fe? O3, TiOz, etc. )enter into the basic silicate lattice. The position of the alkaline earth oxides in the structure of glass requires further investigation. On increasing the content of the tertiary oxides, the dissolution haracteristics show a marked change: alkaline metals and the teri ary oxides are simultaneously driven off from the fiber, and with the appropriate acid treatment, only silica remains in the glass, whose Cal content reaches over 99. The silicate fiber produced from these The same results are obtained by the acid treatment of fibers of certain complex compositions containing a large quantity of alkaline earth-, and sesqui-oxides Investigation of the solubility of fine fibers shows that a charac eristic of most silicate glasses is the presence of a silicate framework 10 which governs in many ways a number of the fiber's properties The marked change in solubility on increasing the tertiary oxide Oxide content o content in ternary or certain more complex glasses gives grounds for suming that this causes a profound change in their structure. As in the sodium borosilicate glasses, so in glasses of other systems with a Fig. 1. The influence of various pecific content of various oxides, the existence of regions of different des on the chemical durability chemical compositions which are differently bonded to the main glass e com leO+ SiO2), 20 Na20, framework is possible. reaction with acid The change in the structure of glass, even when the change in its composition is slight, is confirmed by the investigations of the solubil y of zirconium-containing fibers, conducted by Yu. P. Manko. On the acid treatment of sodium-zirconium silica fibers, only predominantly alkaline oxides are driven off from them. But, on introducing boron oxide into the composition of these glasses, the characteristics of their dissolution exhibit a marked change. Besides the alkall, all the remaining oxides pass into the solution in progressively increasing quantities. Already with a 121 B2O3 content in the glass, the fiber becomes dissolved in the acids, whereupon the highly durable oxides- silica and zirconium dioxide pass into the solution. This effect of even a small quantity of B2Og indicates the destruction of the silicate framework of the glass, and the formation of new structural groups which are readily The silicate framework has been characterized to a considerable extent by the results of investigations into he various properties of silicate fiber, Its heat resistance, chemical durability and electrical properties are close to these same properties in quartz, but in contrast to quartz, the silicate fiber if microporous, as a result of which it has a higher sorption capacity. The fiber's soprtion capacity is sharply reduced through a short heating time Certain of its mechanical properties also deteriorate. Its tensile strength is between 2 and 5 times lower than that of commercial fiber made from nonalkaline glass, depending on the composition of the initial fiber and the conditions of its treatmentcapacity of the silicate fiber is sharply reduced after this. On heating the acid treated fiber from 200~ or over, although it retains its porous structure, its adsorption capacity is again very low. Porous silicate fiber produced from sodium silicate retains its form and has a very high strength reach￾Ing 100 kg/mm 9, From this it follows that the basis of glasses from the composition under consideration is a very strong silicate framework consisting of continuously interlinked SiO 4 tetrahedra. On reaching fibers of a ternary composition which contains up to 1~o tertiary oxides, besides Na20, with acid, alkali are also driven off from them, but nearly all the tertiary oxides remain in the fiber together with the silica (Fig. 1). The thermostability of these fibers, at a sufficient leaching time in accordance with the structural diagram, is somewhat lower than in quartz fiber. The tertiary oxides CaO, ZnO, BaO, PbO, B~Os, TiO,, etc., are fairly firmly bonded in the basic frame￾work when they are contained in the glass in a small quantity. It may be assumed that a number of oxides (A1203, BzO s, Fe~Os, TiO~, etc.) enter into the basic silicate lattice. The position of the alkaline earth oxides in the structure of glass requires further investigation. 35-- ~ ~ 2o 1o 'qez~176 50 tt 8 12 16 Oxide content % Fig. 1. The influence of various oxides on the chemical durability of glass fiber of the composition 8Gr/o (MeO + SiO2), 20% Na20, on reaction with acid. On increasing the content of the tertiary oxides, the dissolution characteristics show a marked change: alkaline metals and the terti￾ary oxides are simultaneourly driven off from the fiber, and with the appropriate acid treatment, only silica remains in the glass, whose content reaches over 99~ The silicate fiber produced from these glasses is not so strong. The same results are obtained by the acid treatment of fibers of certain complex compositions containing a large quantity of alkaline earth-, and sesqut-oxides. Investigation of the solubility of fine fibers shows that a charac￾teristic of most silicate glasses is the presence of a silicate framework which governs in many ways a number of the fiber's properties. The marked change tn solubility on increasing the tertiary oxide content in ternary or certain more complex glasses gives grounds for assuming that this causes a profound change in their structure. As in the sodium borosilicate glasses, so in glasses of other systems with a specific content of various oxides, the existence of regions of different chemical compositions which are differently bonded to the main glass framework is possible. The change in the structure of glass, even when the change in its composition is slight, is confirmed by the investigations of the solubil￾ity of zirconium-containing fibers, conducted by Yu. P. Man'ko. On the acid treatment of sodium-zirconium￾silica fibers, only predominantly alkaline oxides are driven off from them. But, on introducing boron oxide into the composition of these glasses, the characteristics of their dissolution exhibit a marked change. Besides the alkall, all the remaining oxides pass into the solution in progressively increasing quantities. Already with a 1So B2Os content in the glass, the fiber becomes dissolved in the acids, whereupon the highly durable oxides￾silica and zirconium dioxide pass into the solution. This effect of even a small quantity of B20 s indicates the destruction of the silicate framework of the glass, and the formation of new structural groups which are readily soluble in acids. The silicate framework has been characterized to a considerable extent by the results of investigations into the various properties of silicate fiber. Its heat resistance, chemical durability and electrical properties are close to these same properties in quartz, but in contrast to quartz, the silicate fiber if micropomus, as a result of which it has a higher sorption capacity. The fiber's soprtion capacity is sharply reduced through a short heating time. Certain of its mechanical properties also deteriorate. Its tensile strength is between 2 and 5 times lower than that of commercial fiber made from nonalkaline glass, depending on the composition of the initial fiber and the conditions of itc treatment. 609