In previous reports a method of spray drying was developed which produces the fine spherical particles. From the statistical point of view the effects of slip concentration, atomizing velocity and the shape of rotating disc on the distribution of the particle size were studied. It was revealed that the spherical form of the particles thus obtained gives the uniform density distribution in the green body formed by dry pressing and improves considerably the mechanical properties such as hardness.
The present paper contains the results of the studies on the effects of grading of the particles on the hardness distribution in the bodies fired at 1200°-1300C. The relation between the hardness and the density of green body was found to be represented by empirical formulae;
ρ_A=1.35+0.0175R^-1
ρ_B=1.22+0.0193R^-1,
where ρ_A and ρ_B stand for, respectively, the densities of the particles of the irregular and the spherical shape, and R^-1 is the scratch hardness.
For the packing of the particles of uniform size whose mean radius is γ_p the following relations were established;
O₀=0.29-15.0×10^-4γ_p
O_c=0.24-17.1×10^-4γ_p
U₀=0.26-8.4×10^-4γ_p
U_c=0.26-18.2×10^-4γ_p
48<γ_p<88μ,
where, O₀ and O_c are, respectively, the hardness at the perifery and at the center of the end surface of the cylindrical specimen at which the pressure was applied, and U₀ and U_c are, respectively, the hardness at the corresponding points of another end surface.
In the case of mixed powders the condition of uniform packing does not always coincide with that of closest packing, namely, the maximum of the mean density of the green body was confirmed to occur at the size distribution of 20% 88, 20% 62 and 60% 48, while the best condition for the uniform packing would be with the mixture of 50% 88μ and 50% 66μ (Fig. 13, 20).
The hardness distribution of fired body seems to be governed predominately by the degree of sintering; when fired at 1200°C the original distribution in the green body disappeared, and at 1300°C the hardness decreased greatly owing to the evolution of gases in the body, the trend has been noted especially with the finer particles.
This decrease of hardness is considered to be due to the fact that the composition change in each particle has occured as the result of the centrifugal separation in the process of the atomizing of the slip. 20 Fig., 13 Refs.

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The stain and frost which are formed at the surface of some lenses or prisms give the difflculties in using the glass in optical system. They are the abnormal surface layer formed by the surface chemical change.
The authors have carried out the investigations on the nature of the surface layer formed by the attack of gases and liquids on the two kinds of heavy crown glasses, one having high, and the other low chemical durability. The Chemical agent used for attacking the glass surface were; i) water vapor, ii) wet CO₂ gas, iii) wet HCl gas, iv) wet SO₂ gas, v) 1N-HCl solution, vi) 1N-H₃PO₄ solution, vii) 1N-Na₂CO₃ solution, viii) 1N-NH₄Cl solution.
In order to unveil the nature of the surface layer and to know how it was formed the authors have used; a) the observation of the glass surface by phase microscope, b) the measurement of haze value, c) investigation by electron diffraction, d) observation of dew-drops on the surface, e) growth of mould, f) observation of the surface with an electron microscope.
The results of the investigations are summarized as follows: It was revealed that the frost is formed by the attack of gases on the glass surface forming, respectively, Ba(OH)₂. 8H₂O or BaCO₃ by water vapor, BaCO₃ by CO₂, BaCl₂⋅2H₂O by HCl, BaSO₄ by SO₂. In this case the haze per cent is comperatively large.
By the attack of liquid a thin film having the structure of α-quartz mixed partly with Ba-salt is formed. In this case the haze per cent does not become large although interferrence color is observed. It was concluded that the stain of glass surface is observed when a SiO₂-rich film is formed at the surface after the metallic ions were leached out.

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The characteristics of a newly installed vacuum high-frequency induction furnace used for high-temperature experiments are described. A 10, 000 cycle per second motorgenerator of 15kVA output was used as the power source. The heating system, including a water-cooled primary coil 20cm in diameter, a heat insulator and a graphite susceptor 12cm in outer diameter, 14cm high, and 2cm in wall thickness, was placed in a stainless steel vacuum vessel (70cm in inner diameter and 60cm in length) having a steel water jacket.
Graphite powder of 150-200 mesh/in. was used as the heat insulator. A graphite crucible 8cm in outer diameter and 12cm high, set in the graphite suscepter surrounded with a graphite powder insulating layer of 3cm, could be heated up to 3000°C in two hours using a power input of about 7kW. When the graphite crucible itself was used as the susceptor, the insulating layer was 5cm in thickness and the time of heating up to 3000°C was reduced to about one hour with the same power input. When the temperature of the crucible was raised to 2600°C or above, the vaporization of carbon became so noticeable that the fine particles of carbon blew out from the inside of the crucible and carbon vapor deposited in laminar form on the wall of the hole in the lid of the crucible.

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物質の, 温度による結晶構造の変化, 原子配列の変化, 及び物質相互間の溶解度の変化の研究は近年いちじるしくその進歩を見, 各分野でこの方面の測定が行われている.
理学電機ではこの要求にごたえ, 以前連続高温X線カメラを製品化し, 窯業, 金属, 高分子, 無機, 有機化学, 薬学界等に多大の貢献をもたらした. さらに写真法で受けるところの測定結果が写真化されて, 初めてその成果を知ることしか出来ない, 著しい制約を打破する意味で, 計数管を用いた自動記録装置という革命的な手段を提供した. これに伴い, 自動温度制御ということが大きな問題になって来た. そこで精密に各温度, あるいは時間ごとの変化を追う従来の厖大な時間及び労力上の無駄を防ぎ, 問題を短時間で敏速に解決する手段として振動法が考えられた. これは問題となる温度範囲を自動的に往復走査し, これに伴い試料温度を連続的に変化記録する方式で, 時間と共に変化するような析出現象ではその時間変化をチャート上に計録する. 特に温度を自動的に記録出来るという点でこの装置の意義が高く評価されてしかるべきものである. 第1図と第2図は本装置を使用した撮影例である.
上に測定したAl-Zn系というものは, 状態図に異論がありその解決が長い間なされていなかったものであるが, 本装置を利用して測定した結果, よい第3図の状態図の正しいことが実証された.
第3図のような状態図なれば275°まではAl側の固溶体 (面心立方格子) とZn側の固溶体 (稠密六方格子) の相混合の状態にあるが, 275°で同一な面心立方格子で格子定数のみ異なるα+α'なる2相混合物になり, これが350°辺で単相になるところが, 第4図のような状態図であると, 解けるまで単相にならない. 前の第3図より2θを42°と47°間を振動させたところ, 275°を境にZnの線が消失し, Alの線が2本にわかれているのが認められ, これが温度と共に再びAlの線が近づき1本になっている. これより見て第3図の状態図がこの場合正しいものであったことが示されたわけである.

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