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Ammonium tetraborate

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   Ammonium tetraborate   
Names: ammonium tetraborate
ammonium borax
Formula: (NH4)2B4O7 (anhydrous)
(NH4)2B4O7 · 4H2O (tetrahydrate)
Molar mass: 191.315 g/mol (anhydrous)
263.374 g/mol (tetrahydrate)
Density: 1.58 g/cm3 (anhydrous)
2.37 g/cm3 (tetrahydrate)
Crystal system: tetragonal (tetrahydrate)
α=90°, β=90°, γ=90°
Shapes:
https://en.crystalls.info/w/uploads/media/8/8f/Tetragonal_pyramid.json
Tetragonal pyramid

Color: colorless
Decomposition point: 87 °C360.15 K <br />188.6 °F <br />648.27 °R <br /> (tetrahydrate)
Magnetic properties: diamagnetic
Stability: stable (tetrahydrate)
Hardness: relatively strong
Toxicity: non-toxic
LD50=4200mg/kg

Description

Inorganic compound, salt of ammonium ion and inorganic tetraboric acid. From water solutions crystallizes as tetrahydrate.

Precursors

Reaction between ammonia and boric acid

Chemical equation:

4H3BO3 + 2NH4OH = (NH4)2B4O7 + 7H2O


For preparation of 100.00g of ammonium tetraborate tetrahydrate а 106.45g of 25% ammonia and 93.91g of boric acid is required.

Add hot acid to the flask, then add small parts of ammonium compound with stirring until heating will stop (attention, the solution may boil!) . After reaction will stop, 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

Keep in its original form or under several layers of varnish at average humidity and room temperature. Do not keep crystals near heaters.

Solubility

Temperatureg/100,00 g water
(anhydrous)(tetrahydrate)
0°C273.15 K <br />32 °F <br />491.67 °R <br />3.75~5.2
10°C283.15 K <br />50 °F <br />509.67 °R <br />~3.95.3
20°C293.15 K <br />68 °F <br />527.67 °R <br />~5.37.27
25°C298.15 K <br />77 °F <br />536.67 °R <br />9~12.5
50°C323.15 K <br />122 °F <br />581.67 °R <br />21.2~29.2
90°C363.15 K <br />194 °F <br />653.67 °R <br />52.780.7



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   Borates

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



   Ammonium compounds
Salts

Ammonium citrate ((NH4)3C3H5O(COO)3) • Ammonium chloride (NH4Cl) • Ammonium dichromate ((NH4)2Cr2O7) • Ammonium dihydrophosphate (NH4H2PO4) • Ammonium nitrate (NH4NO3) • Ammonium perrhenate (NH4ReO4) • Ammonium sulfate ((NH4)2SO4) • Ammonium succinate ((NH4)2C4H4O4) • Ammonium tetraborate ((NH4)2B4O7) • Ammonium thiocyanate (NH4NCS)

Double salts

Aluminum-ammonium sulfate (NH4Al(SO4)2) • Calcium-ammonium nitrate (5Ca(NO3)2 · NH4NO3) • Chromium(II)-ammonium sulfate ((NH4)2Cr(SO4)2) • Chromium(III)-ammonium sulfate (NH4Cr(SO4)2) • Cobalt(II)-ammonium sulfate ((NH4)2Co(SO4)2) • Cobalt(III)-ammonium sulfate (NH4Co(SO4)2) • Copper(II)-ammonium sulfate ((NH4)2Cu(SO4)2) • Iron(II)-ammonium sulfate ((NH4)2Fe(SO4)2) • Iron(III)-ammonium sulfate (NH4Fe(SO4)2) • Magnesium-ammonium sulfate ((NH4)2Mg(SO4)2) • Manganese(II)-ammonium sulfate ((NH4)2Mn(SO4)2) • Manganese(III)-ammonium sulfate (NH4Mn(SO4)2) • Nickel-ammonium sulfate ((NH4)2Ni(SO4)2) • Sodium-ammonium sulfate (NaNH4SO4) • Vanadium(II)-ammonium sulfate ((NH4)2V(SO4)2) • Vanadium(III)-ammonium sulfate (NH4V(SO4)2) • Zinc-ammonium sulfate ((NH4)2Zn(SO4)2)

Complexes

Ammines • Ammonium dioxalatocuprate(II) ((NH4)2[Cu(C2O4)2]) • Ammonium pentachloroferrate(III) ((NH4)2[FeCl5]) • Ammonium tetrachlorocuprate(II) ((NH4)2[CuCl4]) • Ammonium trioxalatoferrate(III) ((NH4)3[Fe(C2O4)3])

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