CITRIC ACID
Formula: C6H8O7
Preparation
From Molasses: Molasses containing sucrose is diluted with water and then fermented using Aspergillus niger. The microorganism converts the sugar into citric acid.
Test for Purity
- Appearance: The solution must be very clear.
- Arsenic: Less than 1 ppm.
- Barium and Calcium: Less than 100 ppm.
- Heavy Metals: Less than 10 ppm.
- Iron: Less than 50 ppm.
- Chlorides: Less than 50 ppm.
- Sulphates: Less than 150 ppm.
- Oxalic Acid: Identified by treating with calcium chloride.
- Sulphated Ash: Less than 0.1%.
- Moisture: Less than 1%.
Assay
The fermentation is carried out for 7–10 days at a temperature of 26–28°C. The produced citric acid solution is neutralized with calcium hydroxide to form insoluble calcium citrate. This precipitate is washed with water and treated with dilute sulphuric acid to release citric acid. Calcium sulphate formed is filtered off, and the remaining liquid is concentrated under vacuum to obtain citric acid crystals.
Uses
- Used as a mordant in dyeing processes.
- Used in the preparation of esters, which act as plasticizers for lacquers and varnishes.
- Acts as a natural preservative in food, beverages, and pharmaceuticals.
- Used in canning, flavoring, cleaning products, and photographic development.
Detailed Notes:
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