酸化ほう素

外観

白色〜褐色, 結晶性粉末〜粉末

溶解性

水に可溶 (2.8g/100ml, 20℃), エタノールに可溶。

解説

酸化ホウ素(Ⅲ)：B2O3(69.62)．無水ホウ酸，三酸化二ホウ素ともいう．オルトホウ酸を赤熱すると無色のガラス状のものが得られる．密度1.84 g cm－3．融点577 ℃，沸点1500 ℃ 以上．水に溶けてメタホウ酸を経てオルトホウ酸を生じる．両性酸化物で，硫酸，リン酸に溶けてB(HSO4)3，BPO4を生じるが，加水分解するとB2O3を沈殿する．フッ素とは常温で反応してBF3と O2 とを生じるが，ほかのハロゲンとは反応しない．アルカリ金属，マグネシウム，アルミニウムなどで還元される．ギ酸ナトリウムと加熱しても，ホウ素に還元される．炭素では赤熱しても還元されない．耐熱ガラス，光学ガラス，窯業材料，顔料，電子セラミックスなどの原料として用いられる．

用途

ほう素化合物及びガラス加工品原料

用途

ガラス、ガラスファイバ、フリット、セラミック、難燃剤、触媒、産業用オイル、殺生物剤、殺虫剤

用途

発光ダイオード素材?ホウ素化合物原料、ケイ素塩化学分析試薬

用途

吹管分析、ガラス及びセラミック等の原料、無機合成原料、触媒。

化学的特性

Boron oxide is a noncombustible, colorless, semitransparent lumps or hard, white, odorless crystals, with slightly bitter taste.

物理的性質

Colorless glassy solid or vitreous crystal; hexagonal crystal system; slightly bitter taste; hygroscopic; density 2.55 g/cm³; melts at 450°C; vaporizes at 1,500°C; slightly soluble in cold water (3.3%), soluble in alcohol and boiling water (20%).

使用

Boron oxide was used as the intermediate glass layer at a bonding temperature of 450°C. In preparation of fluxes; component of enamels and glass; catalyst in organic reaction.
In metallurgy; in analysis of silicates to determine SiO2 and alkalies; in blowpipe analysis.

製造方法

Boric oxide is produced by treating borax with sulfuric acid in a fusion furnace. At temperatures above 750°C, the molten boric acid layer separates out from sodium sulfate. It then is decanted, cooled, and obtained in 96-97% purity. Boric acid above 99% purity may be obtained by fusing granular material.
Boric oxide may be prepared by heating boric acid.
2B(OH)₃ → B2O₃ + 3H₂O

調製方法

Boric oxide is produced by thermal fusion of boric acid, forming a clear transparent glass-like solid that is subsequently ground into white vitreous granules. It is used principally in the manufacture of glass and vitreous products.

一般的な説明

Colorless, semi-transparent glassy lumps or hard white odorless crystals. Mp 450°C; bp: 1860°C. Density: 2.46 g cm-3. Moderately soluble in water. Used as an insecticide; as the starting material for the synthesis of other boron compounds; as a fluxing agent in enamels and glasses; and in mixture with 2-6% boron nitride, as a bonding agent in the hot isostatic pressing of boron nitride ceramics.

反応プロフィール

Boron oxide is non-combustible. Of generally low chemical reactivity. Reacts exothermically but slowly with water to form boric acid, a weak acid. Reacts exothermically with strong bases. May react with strong reducing agents such as metal hydrides, metal alkyls to generate flammable or explosive gases. May react violently on contact with bromine pentafluoride. Corrosive to metals in the presence of air.

危険性

Eye and upper respiratory tract irritant.

健康ハザード

Boron oxide is an eye and respiratory irritant. In 113 workers exposed to boron oxide and boric acid dusts, there were statistically significant increases in symptoms of eye irrita- tion; dryness of the mouth, nose, and throat; sore throat; and productive cough compared with controls. The mean exposure level was 4.1mg/m3 , with a range of 1.2–8.5mg/m3 . Exposures may occasionally have exceeded 10 mg/m3 . Because of mixed exposures, the study does not indicate whether boron oxide or boric acid dust is more important in causing symp- toms, nor does it indicate the minimum duration of exposure necessary to produce symptoms.
Excessive absorption of boron oxide may lead to cardiovascular collapse, alterations in temperature regulation, and coma.

職業ばく露

Boron oxide is used in glass manufacture and the production of other boron compounds. It is used in fluxes, enamels, drying agents, and as a catalyst.

輸送方法

UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9—Miscellaneous hazardous material, Technical Name Required.

不和合性

Incompatible with bromine pentafluoride, calcium oxide. Reacts slowly with water, forming boric acid. Reacts exothermically with alkaline material and strong bases. May react with strong reducing agents such as metal hydrides, metal alkyls to generate flammable or explosive gases. May react violently on contact with bromine pentafluoride. Corrosive to metals in the presence of air.