Sodium Borate

Borax bp; sodium borate; sodium tetraborate
mf na2b4o7,10h2o --m.wt 381.4 -- cas# 1303-96-4
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 and 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).
Sodium borate usp nf
sodium borate usp-nf; borax usp nf
na2b4o7-10h2o 381.37
borax
borax [1303-96-4]
anhydrous 201.22 [1330-43-4]
sodium borate contains an amount of na2b4o7 equivalent to not less than 99.0 percent and not more than 105.0 percent of na2b4o7·10h2o.
Identification— a solution (1 in 20) responds to the tests for sodium and for borate.
Carbonate and bicarbonate— to 5 ml of a solution (1 in 20), contained in a test tube, add 1 ml of 3 n hydrochloric acid: no effervescence is observed.
Heavy metals— the limit is 0.002%.
Sodium borate de