りん酸せっこうの研究 (第10報)

合成りん鉱石によるおもなる強酸塩の媒晶効果

抄録

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^->SO₄^2->SiF₆^2-.
These effects can be presumed that anions vary diffusion rate of Ca²⁺ and SO₄^2- on to the crystal surfaces and change growth rate of surfaces.