1. 本研究の豫備實驗として1-13種の長石質陶器素地を以て圓板を成形し, 之を1200℃迄締燒し, 之に1-3種の釉を施して1100℃で釉燒を行ひ, 釉燒時間, 釉の厚さ, 成形壓, 釉の粘度及素地の組成と反曲との關係を求め且釉に因る素地の膨脹を測定した。
2. 試驗體は多くは唯1個づつであるから結論を下すことはできないが, 實驗結果は次の通りである。 (1) 釉燒時間の長いとき, 釉の厚いとき, 成形壓の低いとき並に流動性の釉を用ゐたときには反曲が著しかつた。 (2) 素地原料中蛙目, 大峠白士, 蝋石は反曲を小ならしめ, カオリン, 珪石, 長石は反曲を大ならしむる傾向を示した。 (3) 釉は素地の長さを増した。 (4) 1100℃の釉燒時間が2時間に達した場合にはコパルトで着色した釉が可なり深く素地中に滲入した。本實驗の結果だけで見ると反曲は釉の滲入に因ても起り得るやうである。
終りに著者等は本實驗中財團法人旭化學工業奬勵會から研究費の補助を受けた。又佐治タイル合資會社の社長並に五十鈴隆吉, 館野三九馬兩氏は有益な資料と助言とを與へられた。茲に是等法人及3氏に對して衷心の感謝を捧げる次第である。

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1 著者は曩にポルトランドセメントのマグネシアは約8%まで無害であると報告した (本誌, 40, 〔480〕, 769, 昭7)。 更に之を確めんが爲に總て工業原料を用ゐ, 水硬率を2.15に, 珪酸率を2.70に, 鐵率を1.50に一定し, 焼塊が3%, 5%及8%のマグネシアを含有するやう3種の原料配合物を造り, 之をガスマッフル窯で燒成し, 石膏を加へて粉末し, 得たるセメントの小型耐壓力を測定した。
2 材齡3-28日に於てはマグネシア含有量3%と5%の間には殆ど強度の差を見なかつた。 マグネシア8%のセメントは著しく弱かつたが, 他の缺點を認めなかつた。
3 供試體をオートクレブに入れ1400℃で6時間熱した後の強度は, マグネシア5%のセメントは3%セメントに比して著しく優り, 8%のセメントは著しく劣つてゐたが他の缺點を示さなかつた。
4 要するにマグネシアは5%位までは無害で寧ろ有利なやうである。
本研究は文部省自然科學研究奬勵補助費に依つた。 尚著者は化學分析を擔任せられた棚橋壽一氏に對して深く感謝する次第である。

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Durability in water of the glass Na₂O (1-x) CaO, x MgO, y Al₂O₃ 5.3SiO₂, in which x=0-1.0 and y=0-0.2, was determined by the powder method at 95°C (by water bath) and at 170°C (by autoclave)
When y was constant the durability decreased with the increase of x, but the amount of decrease was not so much and became smaller and smaller with the increase of y and at last it became almost insignificant. When x was constant the durability increased with the increase of y
The glass which had greater durability at 95°C had also greater durability at 170°C.

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Taking that the general glass composition is 72% SiO₂, (12-x) CaO, xFe₂O₃, 16K₂O, I have chosen glasses in which the content of x being varies from O to 12, and studied about the variation of the state of oxidation of iron oxide, of the color presented by glasses and of forms of transmission curves.
The process of melting and amount of batches are simila to what I have described in my third report but owing to a difficulty of melting potash glass more than the soda glass the melting temperature applied for the said glass in the experiment has been higher than the normal of 1450°C.
(A) The amount of ferrous oxide contained in the glass and the amount of total oxide expressed in ferric oxide have been obtained by analysis which being as follows: -
The relation between the percentage ratio of FeO/FeO+Fe₂O₃ and the total iron oxide in the glass, appeared in the above table has a tendency similar to that shown in the previous report with the case of soda-lime-silica glass. However, comparing glasses containing same amount of said substance these is formed such a trend that the dissociation of iron oxide in potash-lime-silica glass is less than that in soda-lime-silica glass.
(B) The color and transmission curve of the glasses have been determined.
As to the color those having exceedingly small iron oxide centent present faint bluish green; the color is gradually thickened as the content of iron oxide increases. When the content of total iron oxide reaches as much as 0.5% the glass becomes greenish, along with the increase of iron oxide content yellowish and greenish color are intensified materially and the resultant is that it varies to brownish green until it becomes darkblack glass as the iron oxide content is considerably increased.
Next, colors of soda-lime-silica glasses and potash-lime-silica glasses, both containing approximately same amount of iron oxide, have been compared. In case of thé content of iron oxide is small the color in potash-lime-silica glass is found lighter and clearer and when the said iron content is increased more, and more there is no distinction between the two.
Further, limit wave length which transmit these glasses have been determined from transmission curves obtained through experiment. The re'ation between the iron oxide content and the limit wave length that transmit the glass is quite similar with the soda-lime-silica glass.
Finally, when transmisaion curves of the soda-lime-silica glass and the potash-lime-silica glass are compared it has been formd in general that the transmission in the latter is higher than the former, and this shows the fact that the potash glass is clearer than the soda glass. (Glass research laboratory of The Tokyo Electric Co.)

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