Page 98 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)

Determination of Borax (Na B O )
2 4 7
➢ Borax is used For the treatment of fungal foot diseases (Athlete's foot).

➢ Borax is a component of several commercially available vitamin supplements for Boron.

➢ Thrush, a very common bacterial infection that occurs on the hoofs of horses, can be

treated with the help of borax.

(Borax = Sodium Borate = Sodium Tetraborate = Disodium Tetraborate)
➢ Borax is hydrolyzed in water as follows:.

➢ The liberated NaOH can be titrated against 0.1 M

HCl using M.O. indicator without interference of

boric acid as it is a very weak acid.

E.P ≡ 2 NaOH (from borax)
1
➢ Then borax can be again determined through the

liberated boric acid by adding glycerol to the

above titrated solution (i.e. the solution obtained after E.P ) and then titration against
1
0.1 M NaOH using ph.ph. indicator.

E.P ≡ 4 H BO (from borax)
2 3 3
st
Borax ≡ 2 NaOH ≡ 2 HCl (1 titrant) [ E.P ]
1
nd
Borax ≡ 4 H BO ≡ 4 Glyceroboric acid ≡ 4 NaOH (2 titrant) [ E.P2]
3 3
st nd
If the 1 titrant (HCl) & the 2 titrant (NaOH) have the same concentration, then E.P = 2 E.P
2 1
❖ Notes:

➢ The concentration of borax can be calculated from either E.P or E.P
1 2
➢ Borax is considered a sodium salt of boric acid and the reaction between HCl &

borax is an example of displacement (substitution) titration where HCl

[strong acid] displaces boric acid [very weak acid] in its salts.

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