石膏と石灰
Online ISSN : 2185-4351
ISSN-L : 0559-331X
1971 巻, 112 号
選択された号の論文の6件中1~6を表示しています
  • 1971 年 1971 巻 112 号 p. 79-80
    発行日: 1971/05/01
    公開日: 2011/03/07
    ジャーナル フリー
  • 村上 恵一, 田中 弘文, 秋元 秀敏
    1971 年 1971 巻 112 号 p. 83-92
    発行日: 1971/05/01
    公開日: 2011/03/07
    ジャーナル フリー
    A method for determining the rate of gypsum crystal growth from hemihydrate in crude phosphoric acid aqueous solution was studied. The experimental fact that the feature of original dihydrate seed is visibly preserved in the as-grown dihydrate crystal made the determination of growth rate possible.
    The crystal growth of dihydrate is undergone at a constant temperature (65°C) in metastable zone of hemihydrate after added slightly colorized seed, which is prepared by reaction of calcium chloride and sodium sulphate, to crude phosphoric acid solution containing hemihydrate obtained by decomposition of Fluorida rock phosphate powder with sulphuric acid. Since the original feature of seed crystal is visibly preserved in as-grown crystal, the rate constant of dihydrate growth are determined by measuring the size of as-grown dihydrate crystals and dihydrate seed in it and by applying the rate equation (a*2= (D/ρ) (C-Cs) t+A) derived by Humphreys Owen. Where, a* is equivalent length in the direction of c-axis of crystal of gypsum and C-Cs is solubility difference between hemihydrate and dihydrate in crude phosphoric acid and is constant at definite temperature and definite concentration under present experimental condition.
    By using the method, the precise determination of growth rate of dihydrate crystal is not subject to confuse by irregular neucleation in the hydration process. The rate constants of dihydrate growth in crude phosphoric acid obtained from two kinds of Fluorida rock phosphate are KFnI =2. 4×1022/ hr), KFnII=6.0 × 1022/hr) respectively. The addition of reactive silicic acid to the crude acids increases the rate constants, these are KFsI =2. 5 × 1032/hr), KFsII=1.8×1032/hr) respectively.
    The relation between the equivalent length and growth rate at spontaneous length is a hyperbola, a.* (da*/dt) =K. Therefore, it indicates that the smaller the size of crystal, the larger the rate of growth and the larger the size of crystal, the smaller the rate of growth.
    The present method will can be used for determining the mechanism of solution growth of gypsum crystal and the growth rate of dihydrate crystal in other chemical gypsum productions.
  • 近藤 連一, 大門 正機, 大沢 栄也
    1971 年 1971 巻 112 号 p. 92-96
    発行日: 1971/05/01
    公開日: 2011/03/07
    ジャーナル フリー
    The equations showing the relationship between the rate of water absorption and the pore size of porous materials were studied in connection with the water absorption phenomena in consideration of the various capillary models and also new equations were tentatively derived.
    The water absorption experiments were done by using hydrated α and β-CaSO4·1/2 H2O for examples and the previonsly mentioned equations were applied to the results and some discussions were made. The electrical resistance which changes with absorption of the ionic solution into the specimen was measured for the calculation of the through pore size distribution.
    The results showed that in the case of β-CaSO4·1/2 H2O, the varying radius capillary model in which each capillary has various radius was in good accordance with the structure estimated by the mercury penetration method and the scanning electron microscope observation. While, the pore size distribution of α-CaSO4·1/2 H2O showed good accordance with the meandering capillary model rather than that with the varying radius model. The straight capillary model might be in general inadequate. These facts seem to indicate that the tortuosity is related with either the variation of radius in each capillary or the meandering of each capillary, varying with the sort of specimen.
    It was found that the method to measure the rate of water absorption is valuable to study the pore structure of the materials.
  • 合成りん鉱石によるおもなる強酸塩の媒晶効果
    山田 保, 矢野 貞文, 伊藤 要, 永井 彰一郎
    1971 年 1971 巻 112 号 p. 96-108
    発行日: 1971/05/01
    公開日: 2011/03/07
    ジャーナル フリー
    Crystal growth modifying in various solutions of strong acid salts such as Na2SiF6, NaCl, NH4Cl, NH4Br, NH4NO3, (NH4) 2SO4 and NH4F were studied statistically.
    Hemihydrate gypsum were produced by decomposition of synthesized phosphate rock (fluorapatite which include none of impurities) with H2SO4, and then recrystallized to dihydrate one at 40° and 50°C in the solutions of varions concentration. The size of crystals were measured microscopically as (length × width) 1/2 and obtained following results.
    In the solulions of NazSiF6 (0.1-0.5%), NH4Br (1-5%), NH4NO3 (1-5%), (NH4) 2SO4 (1-5%), gypsum crystallizes needle shaped crystals. In NaCl (1-5%) and NH4Cl (1-5%), crystallizes shorter needle crystals.
    The effect of shortening the crystal form becomes weaker as the anions becomes smaller and the electrolytic dissociation coefficient becomes smaller as Cl->Br->NO3->SO42->SiF62-.
    These effects can be presumed that anions vary diffusion rate of Ca2+ and SO42- on to the crystal surfaces and change growth rate of surfaces.
  • 金沢 孝文, 門間 英毅, 梅垣 高士
    1971 年 1971 巻 112 号 p. 109-116
    発行日: 1971/05/01
    公開日: 2011/08/16
    ジャーナル フリー
    リン酸石灰塩類の代表物質であるフッ素アパタイトCa10 (PO4) 6F2の乾式分解反応式を多数設定して, その反応自由エネルギー変化を試算し, 反応実施の可能性を熱力学的に論じた。フッ素アパタイトの乾式処理の参考資料になると考える。
  • 荒井 康夫
    1971 年 1971 巻 112 号 p. 117-125
    発行日: 1971/05/01
    公開日: 2011/03/07
    ジャーナル フリー
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