Zinc oxide

Japanese: 酸化亜鉛 - さんかあえん（英語表記）zinc oxide

A compound of oxygen and zinc. Often called zinc oxide or zinc white, it is used in industrial chemicals, medicines, pigments, etc. It occurs naturally as zincite.

[Nakahara Katsunori]

Manufacturing method

It is produced by pyrolyzing zinc oxalate, _ZnC2O4 _, at 400°C, or by pyrolyzing basic zinc carbonate, _ZnCO3.3Zn (OH) ₂ . In industry, it is produced by burning metallic zinc.

[Nakahara Katsunori]

nature

Pure zincite is a colorless crystal (zincite is a hexagonal crystal system) or powder at room temperature. When heated to over 250°C, it turns yellow, but returns to its original color when cooled. When strongly heated, it begins to sublime at about 1300°C at 1 atmosphere. It reflects visible light well, but absorbs ultraviolet light well. It emits phosphorescence in sunlight, but emits green or purple light when exposed to cathode rays or anode rays, and emits white thermoluminescence when heated. It is an intrinsic semiconductor. It becomes a phosphorescent material when doped with a small amount of transition metal. It does not decompose even when heated. It is an amphoteric oxide that dissolves in acid to form zinc salts and in aqueous alkali hydroxide solutions to form zincates. It also dissolves in ammonia water and ammonium carbonate aqueous solutions, forming complex salts. When heated with cobalt oxide (CoO), a pigment called cobalt green is obtained.

[Nakahara Katsunori]

Applications

It is used as a white pigment in paints and other colors, as well as in cement, enamel, opaque glass, and as a rubber filler. Fine, high-quality quartz is used in medicines, cosmetics, and dental fillers, and is also a catalyst in the synthesis of methanol (methyl alcohol).

[Nakahara Katsunori]

[References] | Zinc oxide | Zinc ore [Additional information] | Zinc oxide (data note)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

酸素と亜鉛の化合物。工業薬品、医薬品、顔料などとしては亜鉛華、亜鉛白などということが多い。天然には紅亜鉛鉱として産する。

［中原勝儼］

製法

シュウ酸亜鉛ZnC₂O₄を400℃で熱分解するか、塩基性炭酸亜鉛ZnCO₃・3Zn(OH)₂を熱分解させてつくる。工業的には金属亜鉛を燃焼させてつくる。

［中原勝儼］

性質

純粋なものは常温で無色の結晶（紅亜鉛鉱は六方晶系）ないし粉末。250℃以上に加熱すると黄色になるが、冷えるともとに戻る。強熱すると1気圧では約1300℃で昇華が始まる。可視光はよく反射するが、紫外線はよく吸収する。太陽光でリン光を発するが、陰極線、陽極線などで緑色、紫色などの発光をし、加熱すると白色の熱発光をする。真性半導体である。少量の遷移金属をドープ（添加）するとリン光体となる。加熱しても分解しない。両性酸化物で、酸には溶けて亜鉛塩、水酸化アルカリ水溶液に溶けて亜鉛酸塩をつくる。またアンモニア水、炭酸アンモニウム水溶液にも錯塩をつくって溶ける。酸化コバルトCoOと灼熱(しゃくねつ)すると、コバルトグリーンとよばれる顔料が得られる。

［中原勝儼］