1. Assay of Citric Acid Hawzhin A.Salih MSc. Student in
pharmaceutical chemistry

2. Historical point of view
In 1784: calcium citrate was isolated from lemon juice then by H2SO4 producing citric acid.
1880: chemical synthesis from 1,3 dichloro-acetone was one of the crucial method of traditional citric acid production.
1893: the presence of C.A as a calcium oxalate product from the culture of penicillium glaucum fermenting sugar was identified.
From 1913 till now the fungus(Aspergillus niger) replaces p.glaucum for production of citric acid by fermentation process.

3. Production of Citric acid
Today industrial production of citric acid has been restricted to two essential methods:
1.Extraction of Citric acid from fresh fruit juices like lemon, orange and pineapple juices,..etc.
Its production is not significant ,as it comprises less world production.
2.Fermentation of sugar, this process is catalyzed by microorganisms like bacetria (penicillium luterum ,p.glaucum), fungi (Aspergillus niger ,a.wentii), and yeasts (candida lipolytica,c.tropica).
This method is of great industrial value in citric acid production.

4. Uses of citric acid
Most of citric acid products utilities are in food and beverages industry in the world ,owing to acidulant (sour taste), PH adjustment, by the later it can act as preservative in frozen foods. Having an effervescence property make it exist in gaseous soft drinks.
Applications in pharmaceutical preparations, such as suspension and elixir dosage forms to maintain stability of API & improving activities of preservatives.
In cosmetic formulations as PH adjustment and in cooperation with antioxidant systems.
Other applications include in (photography, paper, tobacco and cement industry).

5. Physicochemical properties of Citric acid
It is a white,colourless,odourless and crystalline powder.
It is very soluble in water, freely soluble in ethanol and slightly soluble in ether.
Its melting point is 153°c, decomposition point above 175°c.
According to the presence of water molecule in its structure, it can be divided into two categories: citric acid monohydrate and Anhydrous citric acid.

6. Aim of experiment
To determine the weight of citric acid in a sample solution using titrimetric analysis.

7. Equipments and chemicals
Citric acid monohydrate
Sodium hydroxide 1N
Phenolphthalein indicator
Glasswares and other requirements Burette 50m
Conical flask 250ml
Beaker 50 or 100ml
graduated cylinder 10 or 20ml
burette stand and clamp
White paper

8. procedure
Take 10 ml of an unknown citric acid solution and pour into a 250ml conical flask.
Add 5 drops of phenolphthalein as PH indicator.
Titrate with 1N sodium hydroxide solution.
Addition of NaOH should be drop by drop, until the colour of the analyte solution will be changed from colourless to pink.

9. Calculation At equivalence point:
No. of equivalence of analyte = No. of equivalence of titrant
Wt/Ew(citric acid)= N*V(L)(NaOH)
Wt/64 g/eq = 1N*(0.001)L
Wt(citric acid) = g
So each ml of titrated NaOH is equivalent to 0.064g of citric acid.

10. Normality(N) = no. of equivalence of solute ⁄ volume of solution in Litre
So Equivalence(Eq.) = N*V(L)
at the same time:
Eq. = weight ⁄ equivalence weight
Eq.wt = molecular weight ⁄ valence

11. References
Marin Berovic and Matic Legisa. (2007). Citric acid production. BIOTECHNOLOGY ANNUAL REVIEW, 13.
(2014). Properties of Citric Acid and Its Solutions. In citric acid (Vol. 13, pp ). springer.