Boric acid, บอริกแอซิด, กรดบอริก

กรดบอริก เป็นสารใส ไม่มีสี ไม่มีกลิ่น เป็นผลึกหรือผงสีขาว บางครั้งเป็นเงาคล้ายไข่มุก ละลายได้ดีในน้ำและแอลกอฮอล์ จะละลายได้ดียิ่งขึ้นในน้ำร้อนและกลีเซอรอล กรดบอริกจะระเหยในไอน้ำเมื่อให้ความร้อนถึง 100 องศาเซลเซียส จะสุญเสียน้ำและค่อยๆ เปลี่ยนเป็นเมตาบอริกแอซิด อุณหภูมิ 140 องศาเซลเซียส จะเปลี่ยนเป็นเตตราบอริกแอซิด และที่อุณหภูมิสูงๆ จะเปลี่ยนเป็นโบรอนไตรออกไซด์ (boron trioxide, B2O3) กรดบอริก (boric Acid) ใช้เป็นสารต้านจุลชีพ (antiseptic) เป็นวัตถุกันเสีย (preservative) และใช้เป็นตัวหยุดยั้งการเจริญของเชื้อรา (mold) ในแป้งทาตัว ประกาศกระทรวงสาธารณสุขฉบับที่ 151 (พ.ศ. 2536) เรื่องวัตถุที่ห้ามใช้ในอาหารกรดบอริก เป็นวัตถุที่ห้ามใช้ในอาหาร (prohibit substances) เป็นอันตรายในอาหาร (food hazard) ประเภทอันตรายทางเคมี (chemical hazard) ทั้งบอร์แรกซ์และกรดบอริกมีคุณสมบัติการดูดซึม การขับถ่าย และพิษที่เกิดขึ้นคล้ายคลึงกัน บอริคแอซิ ด (H3BO3) : ช่วยในการเคลื่อนย้ายน้ำตาลไปยั งส่วนต่างๆ ของพื ช ถ้ าขาดสารกลุ่มนี้ พืชจะโตผิดปกติ  หรือหยุดการเจริ ญเติบโต Boric Acid (boracic acid):  White or colorless, smooth crystals or powder, soluble in water, alcohol and glycerin. คุณประโยชน์: เป็นสารเคมีที่ใช้ในอุสาหกรรมเซรามิก, ซิเมนต์, สารประกอบวัตถุกันเสียในอาหาร, เป็นสารสำหรับหนังรวมทั้งการตกแต่งและสารประกอบในการจัดทำหนังก่อนที่จะมีการฟอกหนัง, อัญมนีเทียม, อุตสาหกรรมสี สีเคลือบ, เคลือบกระดาษ, เครื่องสำอาง, สบุ่, ยา, สิ่งทอ

Boric acid, also called hydrogen borate, boracic acid, orthoboric acid and acidum boricum, is a weak acid of boron often used as an antiseptic, insecticide, flame retardant, neutron absorber, or precursor to other chemical compounds. It has the chemical formula H3BO3 (sometimes written B(OH)3), and exists in the form of colorless crystals or a white powder that dissolves in water. When occurring as a mineral, it is called sassolite. 

Uses

Medical

Boric acid can be used as an antiseptic for minor burns or cuts and is sometimes used in dressings or salves. Boric acid is applied in a very dilute solution as an eye wash. Dilute boric acid can be used as a vaginal douche to treat bacterial vaginosis due to excessive alkalinity. As an antibacterial compound, boric acid can also be used as an acne treatment. It is also used as prevention of athlete's foot, by inserting powder in the socks or stockings, and in solution can be used to treat some kinds of otitis externa (ear infection) in both humans and animals. The preservative in urine sample bottles in the UK is boric acid.

Boric acid solutions used as an eye wash or on abraded skin are known to be toxic, particularly to infants, especially after repeated use; this is because of its slow elimination rate.

Insecticidal

Boric acid was first registered in the US as an insecticide in 1948 for control of cockroaches, termites, fire ants, fleas, silverfish, and many other insects. The product is generally considered to be safe to use in household kitchens to control cockroaches and ants. It acts as a stomach poison affecting the insects' metabolism, and the dry powder is abrasive to the insects' exoskeletons.

Preservation

In combination with its use as an insecticide, boric acid also prevents and destroys existing wet and dry rot in timbers. It can be used in combination with an ethylene glycol carrier to treat external wood against fungal and insect attack. It is possible to buy borate-impregnated rods for insertion into wood via drill holes where dampness and moisture is known to collect and sit. It is available in a gel form and injectable paste form for treating rot affected wood without the need to replace the timber. Concentrates of borate-based treatments can be used to prevent slime, mycelium, and algae growth, even in marine environments.

Boric acid is added to salt in the curing of cattle hides, calfskins, and sheepskins. This helps to control bacteria development, and helps to control insects.

Lubrication

Colloidal suspensions of nanoparticles of boric acid dissolved in petroleum or vegetable oil can form a remarkable lubricant on ceramic or metal surfaces[19] with a coefficient of sliding friction that decreases with increasing pressure to a value ranging from 0.10 to 0.02. Self-lubricating H3BO3 films result from a spontaneous chemical reaction between water molecules and B2O3 coatings in a humid environment. In bulk-scale, an inverse relationship exists between friction coefficient and Hertzian contact pressure induced by applied load.

Boric acid is used to lubricate carrom and novuss boards, allowing for faster play.

Nuclear power

Boric acid is used in nuclear power plants as a neutron poison to slow down the rate at which fission is occurring. Fission chain reactions are generally driven by the amount of neutrons present (as products from previous fissions). Natural boron is 20% boron-10 and about 80% boron-11. Boron-10 has a high cross-section for absorption of low energy (thermal) neutrons. By adding more boric acid to the reactor coolant which circulates through the reactor, the probability that a neutron can survive to cause fission is reduced. Therefore, changes in boric acid concentration effectively regulate the rate of fission taking place in the reactor. This method is only used in pressurized water reactors (PWRs). Boron is also dissolved into the spent fuel pools containing used uranium rods. The concentration is high enough to keep neutron multiplication at a minimum. Boric acid was dumped over Reactor 4 of the Chernobyl Nuclear Power Plant after its meltdown to prevent another reaction from occurring.

Industrial

The primary industrial use of boric acid is in the manufacture of monofilament fiberglass usually referred to as textile fiberglass. Textile fiberglass is used to reinforce plastics in applications that range from boats, to industrial piping to computer circuit boards. In the jewelry industry, boric acid is often used in combination with denatured alcohol to reduce surface oxidation and firescale from forming on metals during annealing and soldering operations. Boric acid is used in the production of the glass in LCD flat panel displays.

In electroplating, boric acid is used as part of some proprietary formulas. One such known formula calls for about a 1 to 10 ratio of H3BO3 to NiSO4, a very small portion of sodium lauryl sulfate and a small portion of H

 2SO4. Boric acid, mixed with borax (sodium tetraborate decahydrate) at the weight ratio of 4:5, is highly soluble in water, though they are not so soluble separately. The solution is used for fire retarding agent of wood by impregnation. It is also used in the manufacturing of ramming mass, a fine silica-containing powder used for producing induction furnace linings and ceramics. Boric acid is one of the most commonly used substances that can neutralize active hydrofluoric acid (HF). It works by forcing the free F− anions into complex salts. This process defeats the extreme toxicity of hydrofluoric acid, particularly its ability to sequester ionic calcium from blood serum which can lead to cardiac arrest and bone decomposition; such an event can occur from just minor skin contact with HF. Boric acid is added to borax for use as welding flux by blacksmiths. Boric acid, in combination with silicone oil, is used to manufacture Silly Putty. Boric acid, in combination with eighty other chemicals, is used in Marcellus Shale hydraulic fracturing.

Pyrotechnics

Boron is used in pyrotechnics to prevent the amide-forming reaction between aluminum and nitrates. A small amount of boric acid is added to the composition to neutralize alkaline amides that can react with the aluminum. Boric acid can be used as a colorant to make fire green. For example, when dissolved in methanol it is popularly used by fire jugglers and fire spinners to create a deep green flame.

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