Borax BP; Sodium Borate; Sodium Tetraborate
Na2B4O7,10H2O -- 381.4 -- 10326-27-9
DEFINITION
Borax contains not less than 99.0 per cent and not more than the equivalent of
103.0Â per cent of disodium tetraborate decahydrate.
CHARACTERS
A white, crystalline powder, colourless crystals or crystalline masses,
efflorescent, soluble in water, very soluble in boiling water, freely soluble in
glycerol.
IDENTIFICATION
A. To 1 ml of solution S (see Tests) add 0.1 ml of sulphuric acid and 5 ml of
methanol \ and ignite. The flame has a green border.
B. To 5 ml of solution S add 0.1 ml of phenolphthalein solution. The solution is
red. On the addition of 5 ml of glycerol (85 per cent) the colour disappears.
C. Solution S gives the reactions of sodium.
TESTS
Solution S
Dissolve 4.0 g in carbon dioxide-free water prepared from distilled water andÂ
dilute to 100 ml with the same solvent.
Appearance of solution
Solution S is clear and colourless.
pH
The pH of solution S is 9.0 to 9.6.
Sulphates
15 ml of solution S complies with the limit test for sulphates (50 ppm).
Ammonium
6 ml of solution S diluted to 14 ml with water complies with the limit test
for ammonium (10 ppm).
Arsenic
5 ml of solution S complies with limit test A for arsenic (5 ppm).
Calcium
15 ml of solution S complies with the limit test for calcium (100 ppm).
Heavy metals
12 ml of solution S complies with limit test A for heavy metals (25 ppm).
