Complexometric
Determination of Calcium in
Milk
EXPERIMENT 4
INTRODUCTION

(Ca) is a mineral that can be found in cereals
fruits , vegetables & Dairy products . it is
Essential to the proper formation of teeth and
bones.

increase intake can reduce osteoporosis, a
disease that affects millions where bones
become fragile (bone thinning)

In this experiment the percentage of calcium present
in milk will be determined by using complexometric
titration with EDTA.

EDTA( ethylenediaminetetraacetic) acid is a
hexaprotic ion (chelating agent): meaning that each of
the acid oxygen’s and each of the amine nitrogen’s can
donate one electron pair, and it works by binding to
metal ions (i.e. forms a complex
with calcium ions).
Ca2+ + EDTA→ Ca[EDTA]4-

For EDTA, most metal-ligand complex
formation reactions are fast, stoichiometric and
result in stable compounds.

The clinical determination of calcium in milk is
done by an EDTA titration.

Eriochrome black T (EBT) used as an
indicator.
Reagent:
1. Disodium tetracetic acid (Na2 H2 EDTA. 2H2O)
2. Magnesium EDTA solution 0.1 M .
3. Eriochrome Black T (EBT) indicator solution.
4. Buffer solution.
5. Calcium carbonate (CaCO3) standard 0.8 g/L .
6. Sodium cyanide (NaCN).
7. Unknown I (150 ppm)
8. Unknown II (100 ppm).
Procedure:
5- Titrate with EDTA solution
I) Standardization
until get sky-blue
1234-
color (end point).
10 ml CaCO3
3 ml buffer
4 drops Mg-EDTA
1 drop EBT
II)Analysis
5- Titrate with EDTA
1- 10 ml sample
2- 3 ml buffer
3- 4 drops Mg-EDTA
4- 1 drop EBT
solution until get sky-
blue color (end
point).
CALCULATION:
I)Standardization
Ca titer = (weight of CaCO3mg/ml of EDTA titer) x (volume of
CaCO3ml/1000 ml) x (atomic weight of Ca /M.wt of CaCO3)
Since:
Weight of CaCO3 = 0.8g/L
800mg/1000ml
Volume of EDTA (from my reading) =5.8 ml
Ca titer = (800/5.8) x (10/1000) x (40.08/100.09)
= 137.93 x 0.01 x 0.400
= 0.551 mg/ml
II)Analysis
Concentration of Ca in the unknown sample
= (Ca titer mg/ml x ml of EDTA for unknown) / volume of
sample in liter
Volume of sample = 10 ml
0.01 L
Volume of EDTA from my reading = 1.8 ml
Ca = (0.551mg/ml x 1.8ml) / 0.01L
= 99.18 mg / L