In the preceding report the author have mentioned the relations among the various kinds of precipitated CaCO₃ crystals, namely globular, rhombic, flowery and needle shaped forms, which were obtained by adding (NH₄)₂CO₃ solution to the solution of CaCl₂.
The present paper concerns with another method of preparing CaCO₃ and with the conditions of the appearence of globular and other unstable form as well as the process of the growth of above crystals.
X-ray diffraction method and microscopic observation were jointly used for the identification of the polytypism.
The results are summarized as follows:
1) It was observed that the flowery and needle shaped type grew from the globular type μ-CaCO₃ as shown by the photographic records.
2) The necessary condition for the appearnace of unstable types seems to be the existence of the momentary local supersaturation of Ca²⁺ and CO₃^2-.
3) The appearance of aragonite type crystals was disturbed by the addition of the salts which increase the solubility of CaCO₃.

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The ice-point depression due to thermal after-effect of a thermometer glass reflects upon the fact that the density of a glass quenched from a certain holding temperature is always lower than that of the well annealed specimen even if the holding temperature lies in the region being considerably lower than the transition point.
From the results of the investigations made with lead glasses containing Na₂O, K₂O or both, which presumably show a strong thermal after-effect, the author concluded that the phenomenon is independent of the thermal history of glasses within the limits of experimental errors. Moreover it was found out that the appearance and disappea rance of the density change due to the thermal after-effect is reversible if the effects of compacting may be excluded.
The thermal expansion curves of rapidly cooled glasses showed hysteresis phenomena due to the release of the thermal after-effect. Hence the author was able to draw the curves showing the relations between the degree of the release of thermal after-effect and the reheating temperature.
The thermal expansion curves of the samples with various thermal histories, but free from both compaction and thermal after-effects were also obtained. Furthermore, the relation between the density change and the holding temperature were compared for many glasses having considerably different compositions and properties.

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This is the first report of the studies on titanium carbide cermets carried out by authors, which already have partly presented in 1955 at the general meeting of the Japanese Ceramic Association. Although there are some data necessary to be revised on reference to the later results the authors ventured to present them in the original form, since this paper concerns mainly with the authors' attitude toward the problem as well as with the methods of investigations.
At first, the reason why the authors have used a hydrogen-molybdenum furnace is explained by comparing the properties of the specimens obtained by sintering, respectively, in vacuum high frequency induction furnace and in a Tammann's furnace in hydrogen atmosphere.
Then the flow sheet of the process are illustrated, explaining the apparatus and equipments used for crushing, mixing, pressing and sintering.
Finally, the methods and apparatus for testing the hardness and bending strength and also the results of the microscopic observations are discussed.

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火山作用と関係ある珪酸質岩石5種と硫黄製錬残滓3種について化学分析, 可溶分析, 石灰吸着試験, 水中および飽和石灰乳中における膨脹試験を行った. 無定形珪酸を主成分とする珪酸質岩石は可溶性珪酸分を90-95%を占め, ほとんどアルミナ分を含まないのに対し, 硫黄製錬残滓は可溶性珪酸を約70%, 可溶性アルミナおよび鉄分を10-16%含んでいる. 硫黄製錬残滓の石灰吸着は極めて初期においては著しく大きいが, その後においては経過日数とともに徐々に増加する. それに対して, 珪酸分を主成分とするものは初期の石灰吸着は前者に及ばないが, 経過日数とともに尻上りに増加する. また, 飽和石灰水中の膨脹は石灰吸着の順序と一致しており, 水中においてはいずれも顕著な膨脹は認めなかった. 以上の無定形珪酸を主成分とする岩石および硫黄製錬残滓をセメント混合材として, セメントの10%をこれらと置きかえ, JIS R 5201により1:2モルタルを作製して6ケ月にわたる強度の増進状況を比較した結果, いずれもセメント混合材として良好な性質を有し, 6ケ月後においてはセメント単味のモルタルと同程度の強度あるいはそれを凌駕する効果を示した. 特に硫黄製錬残滓は可溶性アルミナおよび珪酸分を多量に含んでいるので, セメントにこれを混合すれば初期および長期強度の発生が著しく, セメント混合材としてかなり有望と思われる.
本研究は昭和33年4月5日日本化学会第11年会で発表したものである. 実験試料を提供して戴いた日本硫黄KK, 万座硫黄KK, 松尾鉱業所および蔵王鉱業所に対して深甚の謝意を表します.

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