著者

国吉 実 村上 次雄 溝田 忠人

出版者

一般社団法人 資源・素材学会

雑誌

資源と素材 (ISSN:09161740)

巻号頁・発行日

vol.118, no.3,4, pp.191-196, 2002 (Released:2006-01-31)

参考文献数

10

被引用文献数

3 3

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Sodium bicarbonate is so unstable that the rate of decomposition is strongly affected by even trace amount of water in the powder. Variously hydrated species may be formed on the surface as decomposition products from sodium bicarbonate to sodium carbonate. In order to clarify the decomposition-mechanism and chemical-stability of the material, a method of quantitative analysis has necessarily been developed to determine the minute amount of free water and crystalline water related to variously hydrated salts. Preceded to the present work, therefore, four analytical methods established so far were examined to select the suitable method for the present object. The Karl-Fischer titration method combined with a moisture evaporator was finally selected by adding an analytical process, in which the dehydration amount-time profile is deconvoluted into several different peaks corresponding to the state of water. The fractional evaporation of various states of water enables the quantitative analysis without any pretreatment of the sample. This fractional quantitative analysis may be explained by the difference of thermal-stability among those of sodium bicarbonate, sodium carbonate hydrate and sodium sesquicarbonate.

著者

村上 次雄 菊地 光雄 井川 一成 土屋 晉

出版者

公益社団法人 化学工学会

雑誌

化学工学論文集 (ISSN:0386216X)

巻号頁・発行日

vol.20, no.5, pp.618-624, 1994-09-15 (Released:2009-11-12)

参考文献数

8

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次亜塩素酸カルシウム2水和物 (CHDH) は, 偏平な四角板状結晶であり, 固液分離性が劣る, 脆い等, その形状に起因して工業上多くの問題点を有している.このCHDHの晶癖を改善することを目的として, 水酸化カルシウムと水酸化ナトリウムの水性混合スラリーを回分式で塩素化する方法を用いて, 添加剤の効果について検討した.添加剤として多くの無機および有機化合物を用いた結果, カルボン酸化合物および炭水化物に強い媒晶作用を見い出した.この中で多塩基性力ルボン酸化合物が, 実用上有効な添加剤と考えられる.この添加剤の作用は, 結晶の幅 (a, b軸) 方向の成長を抑制し, 厚み (c軸) 方向の成長を促進するものであり, 新しい形状, 即ち単結晶で柱状のCHDH結晶が得られた.添加剤効果のメカニズムとして, (1) 添加剤が結晶の厚み方向の面に選択的に吸着する作用, (2) 添加剤がCa2+とキレートを形成し, 過飽和濃度を高める作用, が考えられる.

著者

国吉 実 村上 次雄 溝田 忠人

出版者

The Mining and Materials Processing Institute of Japan

雑誌

資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan (ISSN:09161740)

巻号頁・発行日

vol.118, no.7, pp.511-516, 2002-07-25

被引用文献数

2

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Sodium bicarbonate easily forms cakes during the storage and / or transport process after production, due to the influence of conditions such as humidity, temperature, compaction etc. Caking causes serious degradation of the material in the commercial value. To overcome the problem, the caking mechanism must be clarified first, and thereafter the effective treatment should be considered to avoid caking. Weak caking strength of sodium bicarbonate powder at the initial stage of caking was measured and evaluated in relation to amounts of various components and physical properties of the powder. Caking under the high humidity (RH80%) of sodium bicarbonate found to occur due to the bridging among particles during the process of changing of sodium carbonate to sodium sesquicarbonate. The caking under the conditions of low humidity (RH40%) and high temperature (40 ∼ 50 °C) however owes bridging accompanied by the change from sodium carbonate to Wegscheider's salt. Caking strengths measured for sodium bicarbonate samples with various particle sizes were correlated with contacting numbers among particles. The caking strength, <i>B_L</i>, was found to be expressed with the equation: <i>B_L</i> = <i>k</i>·<i>Sc</i>·<i>F</i>, where <i>Sc</i> is the contact area per unit surface area of sodium bicarbonate particles, and <i>F</i> is the formation quantity per the unit surface area, of the double salts such as sodium sesquicarbonate and Wegscheider's salt. We have found finally an effective method to avoid caking through the process of analyzing the caking mechanism of sodium bicarbonate.