Boric acid

Boric acid ;
Names:	boric acid; ortoboric acid; boracic acid; hydrogen borate; boron(III) hydroxide; trihydroxyborane; optibor; borofax;
Formula:	H3BO3;
Molar mass:	61.832 g/mol;
Density:	1.435 g/cm3;
Crystal system:	triclinic; a=7.04 Å, b=7.04 Å, c=6.56 Åα=92.5°, β=101.167°, γ=120°;
Shapes:	https://en.crystalls.info/w/uploads/media/1/12/Trapezoidal_flat_prism.json Trapezoidal flat prism https://en.crystalls.info/w/uploads/media/5/50/Beveled_tetragonal_prism.json Beveled tetragonal prism https://en.crystalls.info/w/uploads/media/b/b7/Irregular_hexagonal_pedion.json Irregular hexagonal pedion ;
Color:	colorless;
Melting point:	170.9 °C444.05 K <br />339.62 °F <br />799.29 °R <br />;
Boiling point:	300 °C573.15 K <br />572 °F <br />1,031.67 °R <br />;
Refractive index:	1.456 ;
Magnetic properties:	diamagnetic; χ=-3.41 · 10-5cm³/mol;
Hardness:	very fragile; (1 on Moh's scale);
Toxicity:	non-toxic; LD50=2660mg/kg

Description

Inorganic compound, weak monobasic acid. Doesn't form water hydrates.

Where to buy

Can be bought in pharmacy ("boric acid" in powder).

Precursors

Reaction between borax and sulfuric, hydrochloric or acetic acid

Chemical equation:

Na₂B₄O₇ + H₂SO₄ + 5H₂O = 4H₃BO₃ + Na₂SO₄

Na₂B₄O₇ + 2HCl + 5H₂O = 4H₃BO₃ + 2NaCl

Na₂B₄O₇ + 2CH₃COOH + 5H₂O = 4H₃BO₃ + 2NaCH₃COO

For preparation of 100.00g of boric acid а 154.19g of sodium tetraborate

decahydratedecahydrate
anhydrous

and 107.17g of 37%37% sulfuric or 79.69g of 37%37% hydrochloric or 69.37g of 70%70% acetic acid is required.

Add to the flask with hot tetraborate solution a acid solution with heating and stirring. Cooling this mixture will cause forming a large amount of crystalline precipitate. Filter precipitate and wash it wish small amount of water, alcohol or glycerol, then filter the solution and use it for crystal growing.

Influence of temperature

Very slow crystallization and low transparency at room temperature, but growing from hot solution eliminates these drawbacks.

Storage conditions

Store in its original form or under several layers of varnish at average humidity and room temperature. Do not store in matchboxes or cotton wool and do not heat.

Solubility

TableGraph

Temperature	гр/`100,00` гр water	гр/`100,00` гр ethanol	гр/`100,00` гр methanol	гр/`100,00` гр acetone	гр/`100,00` гр glycerol	гр/`100,00` гр ethyl acetate	гр/`100,00` гр ethylene glycol	гр/`100,00` гр propanol	гр/`100,00` гр isobutanol	гр/`100,00` гр ammonia	гр/`100,00` гр hydrazine	гр/`100,00` гр trichlorethylene
0°C273.15 K <br />32 °F <br />491.67 °R <br />	`2.52`
10°C283.15 K <br />50 °F <br />509.67 °R <br />	`3.49`
15°C288.15 K <br />59 °F <br />518.67 °R <br />	`4.1`											`0.016`
20°C293.15 K <br />68 °F <br />527.67 °R <br />	`4.72`										`55`
25°C298.15 K <br />77 °F <br />536.67 °R <br />	`5.48`	`9.44`	`17.93`	`0.6`	`17.5`	`1.52`	`18.5`	`7.18`	`5.26`	`1.92`
30°C303.15 K <br />86 °F <br />545.67 °R <br />	`6.23`
40°C313.15 K <br />104 °F <br />563.67 °R <br />	`8.08`
50°C323.15 K <br />122 °F <br />581.67 °R <br />	`10.27`
60°C333.15 K <br />140 °F <br />599.67 °R <br />	`12.97`
70°C343.15 K <br />158 °F <br />617.67 °R <br />	`15.75`
80°C353.15 K <br />176 °F <br />635.67 °R <br />	`19.1`
90°C363.15 K <br />194 °F <br />653.67 °R <br />	`23.27`
100°C373.15 K <br />212 °F <br />671.67 °R <br />	`27.53`

Highly soluble in sulfuric acid. Soluble in dioxane.

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Borates
Ammonium tetraborate ((NH₄)₂B₄O₇O) • Boric acid (H₃BO₃) • Copper(II) metaborate (Cu(BO₂)₂ · H₂O) • Sodium tetraborate (Na₂B₄O₇)

Acids

Inorganic

Boric (H₃BO₃) • Disulfozirconium (H₂ZrO(SO₄)₂) • Tetrachlorauric (H[AuCl₄])

Organic

4-Aminobenzoic (H₂NC₆H₄COOH) • Acetylsalicylic (C₉H₈O₄) • Ascorbic (C₆H₈O₆) • Benzoic (C₆H₅СООН) • Citric (C₃H₅O(COOH)₃) • Cyclamic (C₆H₁₃NO₃S) • Glutamic (C₅H₉NO₄) • Glycine (NH₂CH₂COOH) • Oxalic (HOOCСООН) • Phenol (C₆H₅OH) • Phtalic acid (C₈H₆O₄) • Saccarin (C₇H₅NO₃S) • Salycilic (С6Н4(OH)CООН) • Sulfamic (H₂NSO₃H) • Succinic (НООССН2СН2СООН) • Tartaric (C₄H₆O₆) • Trichloroisocyanuric (C₃Cl₃N₃O₃) • Vanillic (C₈H₈O₄)

Boric acid
Names:	boric acid ortoboric acid boracic acid hydrogen borate boron(III) hydroxide trihydroxyborane optibor borofax
Formula:	H₃BO₃
Molar mass:	61.832 g/mol
Density:	1.435 g/cm³
Crystal system:	triclinic a=7.04 Å, b=7.04 Å, c=6.56 Åα=92.5°, β=101.167°, γ=120°
Shapes:	Trapezoidal flat prism Beveled tetragonal prism Irregular hexagonal pedion
Color:	colorless
Melting point:	170.9 °C444.05 K <br />339.62 °F <br />799.29 °R <br />
Boiling point:	300 °C573.15 K <br />572 °F <br />1,031.67 °R <br />
Refractive index:	1.456
Magnetic properties:	diamagnetic χ=-3.41 · 10^-5cm³/mol
Hardness:	very fragile (1 on Moh's scale)
Toxicity:	non-toxic LD₅₀=2660mg/kg