deg""batch' K [OH]2 After fining, the solubility of CO2, H2O, and so, in the glass and therefore the total content of these gases in the glass as sO4, Cos and oH- ions, will depend direct ly on the oxygen introduced into the glass and on the partial pressure of these gases. In the case in which the oxygen is introduced as sodium sulfate, with or without As,O3, the total gas content will be greater than when the oxygen is introduced as calcium nitrate. This is due to the fact that the solution of gases in the glass occurs at the same time from all three reactions and the gas content is due to the Fig 3. The dependence of the gas content of when Ca(NO3)2 4H2O is introduced into the batch, but also t solution in the gla ot only of H,o and CO, which occu Class on the amount of calcium nitrate and 0.3% arsenic trioxide added to the batch (le The role of oxygen as a factor which affects the solu- end as in Fig. 1) tion of other gases in the glass becomes quite clear if Figs and 2 are compared. The introduction of Na?, with As2O3 into the batch, as shown in Fig. 2, more than doubles the O2 content of the glass compared with the addition of Na2 SO4 alone (as in Fig. 1). As the same time there is also an increase in the total gas content of the glass This confirms that it is possible to use the equations above to describe the process of gas solution in glass on melting and fining The equilibrium equations may also be used to describe the decomposition of the gas ions which are chemically bonded to the glass, i.e., the foaming process. The foaming temperature in this case will also be a direct function of the oxygen, water, sodium dioxide, and carbon dioxide content of the glass. The complex interconnection between the foaming temperature and the O2 content in the glass explains the fact that the temperature does not increase indefinitely with an increase in the quantity of O2(Figs. 1-3).With an increase in the oxygen content of the glass the content of H2O, SO, and cO, increases abruptly, i.e., with a large amount of oxygen-containing additives in the batch the oxygen enables a large quantity of H O, Co and SO, to dissolve in the glass and they have the opposite effect on the foaming temperature(they lower it The partial pressure over the melt also clearly has an effect on its foaming temperature, The lower the partial pressure the greater is the probability of the gas ions decomposing (see Eqs. (1))and the glass foaming. The partial pressures of CO2, H,O, and SO, above the glass on reheating, for example in the glas melting vessel, are considerably lower than above the glass in the tank furnace(see Table 1). Therefore a second foaming is observed after heating the glass in the vessel. The foaming is particularly strongly affected by a decrease to zero in the partial pressure of so2 in the melting vessel and by a sudden decrease in the partial pressure of water vapor. Indeed, the foaming temperature of glasses containing SO, (Figs. 1 and 2)is significantly lower than that of glasses which do not contain SO,(Fig 3) Thus, the experimental studies show that by a trial-and-error selection of the batch composition it s possible to regulate the residual gas content of the glass and its foaming temperature. The results con firm the view held by several research workers of the chemical nature of the solubility of such gases as H2O, SO2, O2, and CO2 in glass and indicate the extremely important part played by the oxygen in the glass which affects the control of gas dissolution and gas separation from the glass. The experimental data cor firmed that the chemical equilibrium equations may be used to describe the dissolution in, and separation from the glass, of triatomic gases LITERATURE CITED 1. K. V. Nagulevich and Yu. I Kolesov, Steklo i Keramika, No 6(1969) 2. J. Budd et al.. Glass Technol., 3, No 4(1962)t, foam, Vgas/Vbatch, degr " ~[ z /300 " r ,280- [~/r ,2ooty / "~ - 9 -'- tf40- 800 / r 7001- r162 I t080 - 6OO tObO- 500 /O#O - t000- 300 980 - . # 8 #60 - 2O0 #2O - too Fo~,~ O,o 0,2 o,z~ 0,6 0,8 CACAO, % Fig. 3. The dependence of the gas content of glass on the amount of calcium nitrate and 0.3% arsenic trioxide added to the batch (le￾gend as in Fig. 1). K oP- eco, [o ~-] [OH]= Ko. -- PH,O [0 ~-] " (1) After fining, the solubility of CO2, H20 , and SO 2 in the glass and therefore the total content of these gases in the glass as SO~-, CO 2-, and OH- ions, will depend direct￾ly on the oxygen introduced into the glass and on the partial pressure of these gases. In the case in which the oxygen is introduced as sodium sulfate, with or without As203, the total gas content will be greater than when the oxygen is introduced as calcium nitrate. This is due to the fact that the solution of gases in the glass occurs at the same time from all three reactions and the gas content is due to the solution in the glass, not only of H20 and CO 2 which occurs when Ca(NO3) 2.4H20 is introduced into the batch, but also of SO 2 . The role of oxygen as a factor which affects the solu￾tion of other gases in the glass becomes quite clear if Figs. 1 and 2 are compared. The introduction of Na2SO 4 with As203 into the batch, as shown in Fig. 2, more than doubles the 02 content of the glass compared with the addition of Na2SO 4 alone (as in Fig. 1). As the same time there is also an increase in the total gas content of the glass. This confirms that it is possible to use the equations above to describe the process of gas solution in glass on melting and fining. The equilibrium equations may also be used to describe the decomposition of the gas ions which are chemically bonded to the glass, i.e., the foaming process. The foamingtemperature inthis case will also be a direct function of the oxygen, water, sodium dioxide, and carbon dioxide content of the glass. The complex interconnectionbetween the foaming temperature and theO 2 content in the glass explains the fact that the temperature does not increase indefinitely with an increase in the quantity of 02 (Figs. 1-3). With an increase in the oxygen content of the glass the content of H20 , SO 2 and CO 2 increases abruptly, i.e., with a large amount of oxygen-containing additives in the batch the oxygen enables a large quantity of H20, CO2, and SO 2 to dissolve in the glass and they have the opposite effect onthe foaming temperature (they lower it). The partial pressure over the melt also clearly has an effect on its foaming temperature. The lower the partial pressure the greater is the probability of the gas ions decomposing (see Eqs. (1)) andthe glass foaming. Thepartialpressures of CO2, H20, and SO 2 above the glass on reheating, for example in the glass melting vessel, are considerably lower than above the glass in the tank furnace (see Table 1). Therefore, a second foaming is observed after heating the glass in the vessel. The foaming is particularly strongly affected by a decrease to zero in the partial pressure of SO 2 in the melting vessel and by a sudden decrease in the partial pressure of water vapor. Indeed, the foaming temperature of glasses containing SO 2 (Figs. 1 and 2) is significantly lower than that of glasses which do not contain SO 2 (Fig. 3). Thus, the experimental studies show that by atrial-and-error selection of the batch composition it is possible to regulate the residual gas content of the glass and its foaming temperature. The results con￾firm the view held by several research workers of the chemical nature of the solubility of such gases as H20 , SO2, O2, and CO 2 in glass and indicate the extremely important part played by the oxygen in the glass which affects the control of gas dissolution and gas separation from the glass. The experimental data con￾firmed that the chemical equilibrium equations may be used to describe the dissolution in, and separation from the glass, of triatomic gases. 1, 2. LITERATURE CITED K. V. Nagulevich and Yu. I. Kolesov, Steklo i Keramika, No. 6 (1969). J. Budd et al., Glass Technol., 3, No.4 (1962). 668