Sodium tetraborate

From Crystal growing
Jump to: navigation, search


  Sodium tetraborate   
Names: sodium tetraborate
disodium tetraborate
sodium borate
borax
tincal
tincalconite

Formula: Na2B4O7 (anhydrous)
Na2B4O7 · 5H2O (pentahydrate)
Na2B4O7 · 10H2O (decahydrate)
SMILES: B1(OB2OB(OB(O1)O2)[O-])[O-].[Na+].[Na+]
Molar mass: 201.217 g/mol (anhydrous)
291.291 g/mol (pentahydrate)
381.366 g/mol (decahydrate)
Density: 2.37 g/cm3 (anhydrous)
1.815 g/cm3 (pentahydrate)
1.71 g/cm3 (decahydrate)
Crystal system: monoclinic (anhydrous)
a=5.507 Å
5.5070 Å
0.5507 nm
, b=17.796 Å
17.7960 Å
1.7796 nm
, c=8.377 Å
8.3770 Å
0.8377 nm
α=90°
90°  
, β=96.566°
96°33′57.6″  
, γ=90°
90°  

orthorhombic (pentahydrate)
α=90°
90°  
, β=90°
90°  
, γ=90°
90°  

monoclinic (decahydrate)
a=11.884 Å
11.8840 Å
1.1884 nm
, b=10.602 Å
10.6020 Å
1.0602 nm
, c=12.2111 Å
12.2111 Å
1.2211 nm
α=90°
90°  
, β=106.79°
106°47′24.0″  
, γ=90°
90°  

Forms:
https://media.crystalls.info/w/uploads/media/Prolongated_hexagonal_flat_prism.json
https://media.crystalls.info/w/uploads/media/Octahedron.json
https://media.crystalls.info/w/uploads/media/Tetragonal_pyramid.json

Color: colorless
Melting point: 742 °C
1,015.15 K
1,367.6 °F
1,827.27 °R
(anhydrous)
140 °C
413.15 K
284 °F
743.67 °R
(pentahydrate)
Decomposition point: 1575 °C
1,848.15 K
2,867 °F
3,326.67 °R
(anhydrous)
Refractive index: 1.462 (decahydrate)
1.468 (pentahydrate)
Magnetic properties: diamagnetic
Stability: slightly erodes (decahydrate)
stable (pentahydrate)
Hardness: relatively strong
Toxicity: non-toxic

Description

Inorganic compound, salt of alkaline metal sodium and inorganic tetraboric acid. From water solutions crystallizes as decahydrate and pentahydrate.

Minerals

Occurs in nature as tinkal mineral.

Where to buy

In pharmacy ("borax" as powder or glycerol solution).

Precursors

Reaction between baking soda, sodium carbonate or hydroxide and boric acid

Chemical equation:

4H3BO3 + 2NaHCO3 = Na2B4O7 + 7H2O + 2CO2
4H3BO3 + Na2CO3 = Na2B4O7 + 6H2O + CO2
4H3BO3 + 2NaOH = Na2B4O7 + 7H2O

For preparation of 100.00g of sodium tetraborate decahydrate а 44.06g of soda or 27.79g of carbonate or 20.98g of sodium hydroxide and 64.85g of boric acid is required.
Add acid to the flask, then add small parts of sodium compound with stirring until heating will stop (attention, the solution may boil!) or, if you use carbonate, until carbon dioxide emission will stop. 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. If temperature is over decahydrate decomposition temperature, a pentahydrate crystallization starts with another crystalline final form.

Influence of impurities

Notes

Crystal can thicken after several months due to eroding.

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

Temperatureгр/100,00 гр waterгр/100,00 гр ethanolгр/100,00 гр methanolгр/100,00 гр acetoneгр/100,00 гр glycerolгр/100,00 гр ethyl acetateгр/100,00 гр ethylene glycol
(anhydrous)(pentahydrate)(decahydrate)(decahydrate)(decahydrate)(decahydrate)(decahydrate)(decahydrate)(decahydrate)
0°C
273.15 K
32 °F
491.67 °R
1.11
1.11 g/100g
1.098 %
2.04
2.04 g/100g
1.999 %
10°C
283.15 K
50 °F
509.67 °R
3.19
3.19 g/100g
3.091 %
15°C
288.15 K
59 °F
518.67 °R
3.94
3.94 g/100g
3.791 %
2.54
2.54 g/100g
2.477 %
20°C
293.15 K
68 °F
527.67 °R
4.94
4.94 g/100g
4.707 %
110.97
110.97 g/100g
52.6 %
25°C
298.15 K
77 °F
536.67 °R
6.16
6.16 g/100g
5.803 %
24.84
24.84 g/100g
19.897 %
0.6
0.6 g/100g
0.596 %
0.14
0.14 g/100g
0.14 %
71.23
71.23 g/100g
41.599 %
30°C
303.15 K
86 °F
545.67 °R
7.76
7.76 g/100g
7.201 %
40°C
313.15 K
104 °F
563.67 °R
12.64
12.64 g/100g
11.222 %
50°C
323.15 K
122 °F
581.67 °R
15.87
15.87 g/100g
13.696 %
21.82
21.82 g/100g
17.912 %
60°C
333.15 K
140 °F
599.67 °R
~17.9
17.9 g/100g
15.182 %
43.53
43.53 g/100g
30.328 %
70°C
343.15 K
158 °F
617.67 °R
20
20 g/100g
16.667 %
58.58
58.58 g/100g
36.94 %
80°C
353.15 K
176 °F
635.67 °R
23
23 g/100g
18.699 %
79.57
79.57 g/100g
44.311 %
90°C
363.15 K
194 °F
653.67 °R
28
28 g/100g
21.875 %
113.58
113.58 g/100g
53.179 %
100°C
373.15 K
212 °F
671.67 °R
52.5
52.5 g/100g
34.426 %
35
35 g/100g
25.926 %
191.04
191.04 g/100g
65.64 %

Gallery


Video


Sources


Navigation