TABLE 1 heating, changes in the partial gas pressure over the melt) Fartial pressure of gases over the glass, may be de composed with the separation of these gases and Gas oxygen in their molecular forms. Since the physical solubi ank furnace glass-melting vessel lity of these gases in the batch is insignificant they form a free gas phase in the glass, as bubbles or even as continu CO, 3 From the law of chemical equilibrium it can be as sumed that an increase of oxygen in the batch will impede the decomposition of the complex ions leaving them in a chem- ically bonded state and will prevent the foaming of the glass. The purpose of this work therefore was to study the effect of various oxygen-containing additives on the character and total amount of gas in the glass and on its foaming temperature. In parallel with these additions arsenic trioxide, an oxide of a variabl valency metal, was added to the batch thus facilitating the solution of oxygen in the glass Specimens of glass to which various amounts of sodium sulfate, calcium nitrate, and arsenic tr oxide had been added, were melted in platinum crucibles in an electric resistance-heated muffle furnace temperature were determined using the method recommended by the All-Union Scientific-Research Insti tute of Glass Plastics and Glass Fibers [6] The change in the foaming temperature of the glass and the character and magnitude of its gas con tent are shown in Figs. 1 to 3 as a function of the type and quantity of the additives. The introduction of each additive, As2O3, Na2 SO4, Ca(NO3)2. 4H2O; Na2 SO4+ As2O3, Ca(NO3)2 4H2O+ As2O3, at first decreased the gas content in the glass, reduced the amount of CO2 and H,O, and increased the oxygen and sulfur dioxide content with a simultaneous increase of the foaming temperature of the glass. At this stage, when the quantity of the additives, expressed in terms of Cao and NaO, is less than 0.4% Cao or Na,O, they act both as fining additives decreasing the gas content in the glass and also as additives which increase the O2 content and stabilize the chemical bond between the gas ions and the components of the glass when it is which separates from the glass as bubbles, decreases the partial pressure of the residual gases in the The role of the oxygen as a fining agent in this case confirms the generall bubbles and enables other gases to flow from the glass into the bubbles and so to escape from the glass i. e, the gas content of the glass is decreased. With such a relatively low oxygen content introduced with the additives its role in the formation of a large quantity of complex gas ions chemically bonded to the glass when the glass is made, is clearly insignificant, but it is completely adequate for their stabilization in the glass on reheating. In these cases, therefore, the oxygen-containing additives decrease the amount of all the gaseous components in the glass(apart from oxygen) and increase the temperature at which the complex ions decompose, i. e, the foaming temperature be seen from Figs. I to 3)leads to an increase in the formation of complex ions of triatomic gases whlch p When the concentration of oxygen-containing additives is further increased, the excess oxygen(as significantly increases the total content of all the gaseous components in the glass. Nevertheless, the values of the foaming temperature remain at the former high value and only decrease slightly when there is a sufficiently large amount of oxygen-containing additives( Cao and Na,O content greater than 0.6 to 0.8% and still remain above the foaming temperature of the glass made without additives The dependences shown in Figs. l to 3 also indicate that under similar conditions the efficiency of the effect on the gas content and foaming temperature of the glass is not the same for different oxygen- containing additives. Thus, the greatest decrease in the total gas content in the glass and the highest value of the foaming temperature is reached after reheating when Ca(NO3)2 4H2O together with As,O3 is added to the glass. The solubility of oxygen in the glass is also greatest in this case As an approximate description of the processes involved in the solution of gases in glass on melting fining, and decomposition of the chemically bonded gaseous complexes on reheating, the following equili brium equationTABLE 1 Eartial pressure of gases over the glass, Gas mm Hg tank furnace glass-melting vessel CO~ Ne H20 02 S02 73,6 522,0 151,0 13,4 0,2 ~2 36 152 heating, changes in the partial gas pressure over the melt) may be decomposed with the separation of these gases and oxygen in their molecular forms. Since the physical solubi￾lity of these gases in the batch is insignificant they form a free gas phase in the glass, as bubbles or even as continu￾ous foam. From the law of chemical equilibrium it can be as￾sumed that an increase of oxygen in the batch will impede the decomposition of the complex ions leaving them in a chem￾ically bonded state and will prevent the foaming of the glass. The purpose of this work therefore was to study the effect of various oxygen-containing additives on the character and total amount of gas in the glass and on its foaming temperature. In parallel with these additions arsenic trioxide, an oxide of a variable valency metal, was added to the batch thus facilitating the solution of oxygen in the glass. Specimens of glass to which various amounts of sodium sulfate, calcium nitrate, and arsenic tri￾oxide had been added, were melted in platinum crucibles in an electric resistance-heated muffle furnace. The fining time for all the glasses was kept constant and was 1 h at 1500~ The gas content and foaming temperature were determined using the method recommended by the All-Union Scientific-Research Insti￾tute of Glass Plastics and Glass Fibers [6]. The change in the foaming temperature of the glass and the character and magnitude of its gas con￾tent are shown in Figs. 1 to 3 as a function of the type and quantity of the additives. The introduction of each additive, As203, Na2SOr Ca(NO3) 2.4H20; Na2SO4+ As203, Ca(NO3) 2-4H20+ As203, at first decreasedthe gas content in the glass, reduced the amount of CO 2 and H20 , and increased the oxygen and sulfur dioxide content with a simultaneous increase of the foaming temperature of the glass. At this stage, when the quantity of the additives, expressed in terms of CaO and Na20, is less than 0.4% Ca(9 or Na20 , they act both as fining additives decreasing the gas content in the glass and also as additives which increase the 02 content and stabilize the chemical bond between the gas ions and the components of the glass when it is reheated. The role of the oxygen as a fining agent in this ease confirms the generally accepted view. Oxygen, which separates from the glass as bubbles, decreases the partial pressure of the residual gases in the bubbles and enables other gases to flow from the glass into the bubbles and so to escape from the glass, i.e., the gas content of the glass is decreased. With such a relatively low oxygen content introduced with the additives its role in the formation of a large quantity of complex gas ions chemically bonded to the glass when the glass is made, is clearly insignificant, but it is completely adequate for their stabilization in the glass on reheating. In these cases, therefore, the oxygen-containing additives decrease the amount of all the gaseous components in the glass (apart from oxygen) and increase the temperature at which the complex ions decompose, i.e., the foaming temperature. When the concentration of oxygen-containing additives is further increased, the excess oxygen (as can be seen from Figs. 1 to 3) leads to an increase in the formation of complex ions of triatomic gases which significantly increases the total content of all the gaseous components in the glass. Nevertheless, the values of the foaming temperature remain at the former high value and only decrease slightly when there is a sufficiently large amount of oxygen-containing additives (CaO and Na20 content greater than 0.6 to 0.8%) and still remain above the foaming temperature of the glass made without additives. The dependences shown in Figs. 1 to 3 also indicate that under similar conditions the efficiency of the effect on the gas content and foaming temperature of the glass is not the same for different oxygen￾containing additives. Thus, the greatest decrease in the total gas content in the glass and the highest value of the foaming temperature is reached after reheating when Ca(NO3) 2.4H20 together with As203 is added to the glass. The solubility of oxygen in the glass is also greatest in this case. As an approximate description of the processes involved in the solution of gases in glass on melting, fining, and decomposition of the chemically bonded gaseous complexes on reheating, the following equili￾brium equations can be used: . [so, Kso~-= Pso~- Po, '~/~ [o ~- l, ' 667