In order to trace the cause of cracking phenomenon of clay body during steady heating in a saturated atmosphere, some experiments were conducted with some clays which were treated with different methods.
The main results are summarized as follows:
(1) The actual range over which cracking takes place is a property of clay.
(2) Drying treatment of a raw clay reduces the critical temperature at which cracking commerces.
(3) The unequal condition or included air in clay body do not effect cracking in a saturated atmosphere.
(4) The critical temperature at which cracking commerces is influenced by introducing salt solutions, and the alkali solution increases that temperature.
(5) There is a definite relationship between the critical temperature and the moisturecontent of the clay.

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The infrared absorption spectra in the range of the wave length from 2 to 25μ have been investigated on arsenic-sulfur glasses, including plastic sulfur, directly prepared in the film form by the evaporation under normal pressure using the evaporation outfit and operating condition shown in the previous paper (Reference 6). Each of the arsenic-sulfur glasses itvestigated here was allowed to cool in atmospheric gas after the condensation in the molten state on the back-surface of aluminum target for rather short time (5-20 min), and was separated from the target by the chemical procedure using dilute hydrochloric acid. The spectra recorded for the above arsenic-sulfur glasses of the composition ranging from As₂S_2.8 to As₂S_15.4 were 9.58±0.05μ(1044±6cm^-1) accompanied by the absorption band at 12.67±0.02μ(789±2cm^-1), 9.55±0.05μ(1047±6cm^-1) appeared without the absorption band at 12.67±0.02μ(789±2cm^-1), 11.95±0.15μ(837±11cm^-1), 12.51±0.05μ(799±4cm^-1), 12.67±0.02μ(789±2cm^-1), 14.84±0.11μ(674±5cm^-1), 15.18±0.05μ(659±3cm^-1) appeared together with the absorption band at 20.69±0.08μ(483±2cm^-1), 19.93±0.07μ(502±2cm^-1), 20.69±0.08μ(483±2cm^-1), 21.09±0.10μ(474±3cm^-1) and 21.36±0.10μ(468±2cm^-1). The spectra for the plastic sulfur were 7.66±0.03μ(1305±6cm^-1)(w), 10.71±0.05μ(934±5cm^-1)(vw), 11.04±0.03μ(906±3cm^-1)(vw), 11.43±0.03μ(875±2cm^-1)(vw), 11.95±0.15μ(837±11cm^-1)(s), 14.06±0.03μ(711±2cm^-1)(w), 14.65±0.05μ(683±3cm^-1)(vw), 15.20±0.05μ(658±3cm^-1)(w) appeared without the absorption band at 20.69±0.08μ(483±2cm^-1), 19.50±0.20μ(513±6cm^-1)(vw) and 21.36±0.10μ(468±2cm^-1)(s), where s, m, w and vw denoted strong, medium, weak and very weak bands, respectively.
No absorption bands due to dissolved gases have appeared for arsenic-sulfur glass films used in the present investigation. Contrary to the observation by Kolomiets and Pavlov (Reference 4) that the absorption band at around 12.5μ was not appeared for “As₂S₃ and As₂S₃⋅As₂Se₃ glasses” but for “As₂S₃⋅2As₂Se₃ and As₂Se₃ glasses” which were all synthesized according to the procedure by Goryunova, Kolomiets and Shilo (Reference 10), the absorption bands at around 12.67μ(789cm^-1)(s) and around 12.51μ(799cm^-1)(m) have been respectively recorded for glasses of the compositions near As₂S_2.8 and As₂S_8.6 which were both prepared from the nearly selenium-free batches by the present evaporation and condensation method.
A satisfactory assignment of the absorption bands recorded for the above glasses of the arsenic-sulfur system has been made mainly from the relationship among glass compositions and band characteristics (the position, broadness, sharpness and intensity of band) and from the comparison of band characteristics among glasses and plastic and crystalline sulfurs, as follows: (1) the absorption band appeared at around 12.51μ(799cm^-1) is attributed to the vibration of As=S bond (the As-S bond with an increased double bond character) in the As₂S₅ glass

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Following the previous reports on borate and silicate systems, we studied the glass-formation range of germanate systems. Germanate glass has a structure similar to that of silicate However, these systems have not been sufficiently studied and practically utilized, because germanium is a rare element. The molecular weight of Ge is nearly three times as large as that of Si. Therefore, germanate glass, compared with silicate glass, has a larger density, refractive index and expansion coefficient, a lower melting point, and a wider range of infrared transmission.
This experiment used the same kind of oxides and the same amount of melts as did the previous experiments; the melts were melted at temperatures from 1200 to 1500°C. As germanate systems are melted by gas, it must be remembered that GeO₂ sometimes attacks platinum crucibles, especially in systems containing ThO₂. Therefore, experiments over a large part of the ThO₂-systems were stopped.
The glass-formation ranges of binary systems are shown in Table 1. The modifier ions of this system are alkali and alkaliearth, but the Mg-ion, which is a modifier of the silicate system, is not present. This is perhaps because the acidity of germanium oxide is weaker than that of silicon oxide. In the germanate as well as the silicate system, the width of the glass formation range of the binary system is parallel to the ionic radius of the modifier, but the difference between the width of the ranges of the large and small modifiers is greater than in the silicate. This difference may be explained as resulting from the fact that the glass-forming ability of germanium oxide is weak and that, therefore, the effects of the condition for the fittest ionic radius of modifier are large. The glass-formation range of the BaO-system, like that of the tellurite system, is divided into two parts. Concerning the limited composition of the immiscible range, the calculated values from Levin's equation agreed with the experimental values (cf. Table 2).
The glass-formation ranges of ternary systems are shown in Fig. 1-35. The number of systems studied reached about 90. The experimental results show that the actual glass-formation rages agree with the ranges (hatched areas in the figures) to be expected from the “Conditions of Glass Formation.” The following systems of germanaes are remarkable: in the GeO₂-Li₂O-BaO system (Fig. 5) and the GeO₂-Al₂O₃-CaO system (Fig. 7), the glassformation ranges are divided into two parts. In BaO-binary systems, the vitrified range is sometimes divided into two parts, but in BaO-ternary systems it is seldom divided. Moreover, in a SiO₂ (or B₂O₃)-Al₂O₃-CaO system, the glass-formation range is not divided. The reason for separation in a germanate system is not a difference in tendency to polymerize between the glass-formers of Ge and Al, but, rather, the weak glass-forming ability of GeO₂. In a system containing TiO₂, like silicate, a limited line of the glass-formation becomes the AC-line; therefore, the coordination number of Ti becomes 4. Moreover, in the germanate system also potassium has the widest vitrified range. (This fact agrees with the rule of the suitable ionic radius of the modifier.) Systems containing WO₃, on the contrary, resemble the borate system; the glass-formation range of alkali tungstate has two tails (cf. Fig. 20). We considered in the silicate system the glass-formation range of the left tail, which consists of WO₃+alkali-germante, is in an immiscible state, with a large difference in the tendency to polymerize between the two glass-formers (Si and W). The binary systems containing La₂O₃ or MgO systems have no vitrified ranges; therefore, these ternary systems have C-type glass-formation ranges. The glassformation

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