Heats of formation for some glassy and crystalline sodium phosphates were investigated by measuring their heats of solution in distilled water and in 3N-HNO₃ aq. using a microcalorimeter.
The glass samples used in this study were prepared from reagent grade NaOH and H₃PO₄ through dehydrating condensation, that is, these reagents were mixed in such proportions that the resulting glasses possessed given chemical compositions and heated in a platinum crucible at 700° to 800°C for 2 hours to drive off water. The samples thus obtained were chemically analyzed for a constituent P₂O₅ and “residual water” which reached a maximum content of 2.5wt%.
In this study the solution calorimetry was made with a twin type differential microcalorimeter in which the quantity of heat is measured as difference of the electromotive force produced with the thermomodules. The detecting sensitivity is 6.5mV/°C, and the thermostat is regulated within ±1μV. Both the time and the temperture difference were successively plotted in a recorder and the quantity of heat was measured as an area enclosed between the temperature curve and the time-axis, which was later compared with a standard heater for correction.
It was confirmed by paper chromatography that both the glassy and crystalline samples were decomposed into orthophosphate molecules with 3N-HNO₃ aq.. The heats of solution for water and 3N-HNO₃ aq. at 25°C were found to be exothermic and the dependence of the chemical composition is shown in Figs. 9 and 10 where a minimum is seen near the meta composition on the curve of the phosphate glasses.
At the stoichiometric meta composition the enthalpy difference between the glassy and crystalline samples was estimated to be about 21cal/g and the heat of formation of NaPO₃ glass from Na(s), P(s) and O₂(g) states was of about 277kcal/mole. The increase of ΔH in the ultra phosphate region may be attributed to hydrolysis of branching points in chain structure but the increase in the polyphosphate region can be explained by increase of P-ONa→P-OH ion-exchange reaction because the long chain structure is more easily cut by Na⁺ ions with increasing Na₂O content in the glass. The enthalpy change associated with annealing of the glass was thought to be negligible small.

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Optical absorption spectra were obtained for series of xLi₂O-(100-x)B₂O₃-(x/10)NiO and xNa₂O-(100-x)B₂O₃-(x/10, and x/20)Nio. Ni²⁺ ions in these glasses were found to be surrounded by six oxygen ions predominantly. The values of octahedral field strength Dq and of the Racah _B parameter which represents Coulombic repulsion between d-electrons of Ni²⁺ ions were calculated from these data. The Dq value decreased slightly with increase of alkali metal oxide content in the composition range of x=10-17 and then the value increased until x reached 20. When the more alkali metal oxide was added, the Dq value of the glasses began to decreased again. The B parameter increased at first with increasing amount of alkali metal oxide in the region of x=10-17, but it decreased considerably at x=17. In the more basic region the B value became bigger again.
The anomalous changes in the two parameters has been tried to be accounted for on the basis of ligand field theory. In this argument it is suggested that π-bonding character in Ni-O bond becomes predominant in the composition range of x=17-20.

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The process of removal of potassium ions from the ion-exchanged sheet glass by electrolysis was investigated.
A commercial sheet glass in which potassium ions were introduced by electrolysis below its strain point was subjected to the second electrolysis under the reverse elecctric field. The potassium ions were removed from the ion-exchanged layer according to the current passage, while the potassium ions were simultaneously introduced into the anode-side surface.
The concentration of potassium ions remaining in the layer on the cathode-side after the second electrolysis decreased monotonically with the depth of the layer.
The apparent electric resistivity ρ of the glass, during the second electrolysis, increased appoximately linearly with increase of thickness, ε, of the ion-exchanged layer on the anodeside except at the beginning of the electrolysis. The relation was expressed by the equation: ρ≅ρ₀+ρ₁ε/L, where L is the thickness of the glass sheet, and ρ₀ and ρ₁, constants related to the resistivity.
The stress profile, which was measured by means of a polarizing microscope, in the layer redistributed with potassium ions was similar to the concentration profile of potassium ions, but the compressive stress was considerably lower than that before the redistribution.
The sheet, bent in order to balance stresses due to the first ion exchange, returned flat as the amount of electricity was passed half as much as that at the first electrolysis. The phenomenon could not be explained by the balance of stresses in the glass, because a considerable difference in stress between the both sides of the glass sheet exists. This is attributed to the dilatation of network cavities by a viscous flow due to the compulsory migration of potassium ions.
On a basis of a theory of electromigration of ions in columns of a cation exchange resin, the redstribution of potassium ions and the variation of resistivity with the amount of electricity passed in the second electrolysis were derived: c_k=a-bz^1/2, and ρ=ρ₀+ρ₁ε/L+ρ₂^′ε^/3/2ε^-1/2/L respectively, where a and b are constants; z, the distance from the boundary of the layer redistributed with potassium ions; ρ₀, ρ₁ and ρ₂^′, constants related to the resistivity; ε, the thickness of the layer in which potassium ions were introduced on the anode-side; L, the thickness of the glass sheet and ε^′, the thickness of the layer in which potassium ions redistributed. These equations agreed fairly with the experimental results.

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Experimental data of the densification rate of BeO compacts, hot-pressed in graphite dies for 1275° to 1700°C and for 115 and 289kg/cm², showed that the densification rate during final stage is described by;
dρ/dt=10σ_aDΩ/R²kTρ^1/2
which has been derived by combination the effective stress with the Nabarro-Herring microcreep in the previous study.
Plots of the densification rate vs ρ^-1/2 are fitted well with two straight lines; the lower slopes represent the final stage of densification which are predicted by this theoretical equation, the higher slopes suggest diffusional transport of materials based on grainboundary diffusion and/or grain-boundary sliding.
Although this densification and Murray's one, both are justified by the linear relationship in ρ^3/2 vs t and -ln(1-ρ) vs t, but the former can predict a time necessary for the compact to be theoretical density, it gave more reasonable conclusion.
Non linear relationship between dρ/dt and ρ^-1/2 prevails in lower temperature, suggests that the densification is contributed by certain slip mode, as a basal slip, concurrent with a pore structure variation.

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The effect of oxygen pressure on sintering of zinc oxide has been investigated by measuring isothermal shrinkage of compacts at 750° and 850°C. The sinterability was proportional to Po₂^-1/5.4 at 750°C in oxygen atomsphere (Po₂>2.5×10^-2torr) and to Po₂^-1/5.4 at 850°C in Po₂>3×10^-3torr. The result indicates that the sintering process is controlled by diffusional transfer of interstitial zinc ions. In the lower oxygen pressure, the sintering rate was independent of the pressure. This result was explained by the cooperation of two different mechanisms, i.e., diffusional transfer of interstitial zinc ions and lattice formation process between interstitial zinc and oxygen.

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Thermal expansion of reheated SiO₂-Al₂O₃-K₂O-Na₂O glasses has been related to the formation of leucite crystals in them by determining the amount of leucite precipitated upon reheating and the thermal expansion coefficients of reheated glassses, leucite crystal precipitated in the glass and glass of the composition corresponding to residual glassy matrix in the reheated samples. The following results were obtained.
1) Leucite crystals were precipitated in glasses upon reheating them at 700°-1200°C. The amount of leucite crystals precipitated in glasses increased as the temperature of reheating was lowered and the composition of glass approached the theoretical leucite composition.
2) The linear thermal expansion coefficient measured below 400°C of the reheated glass increased linearly with increasing amount of leucite crystals precipitated in the glass, changing from 10.7×10^-6 to 17.8×10^-6/°C for 0 to 47wt% leucite.
3) The thermal expansion coefficient below 400°C of leucite crystals precipitated in the glass was α_??_=-15.5×10^-6/°C (parallel to the c-axis), α_⊥=39.5×10^-6/°C (perpendicular to the c-axis) and (α_??_+2α_⊥)/3=21.7×10^-6/°C (average).
4) The thermal expansion of the reheated glass was given as the sum of those of leucite crystals and residual glass, and the anomalously high expansion of the reheated glasses was attributed to the high expansion leucite crystals.

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