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DrX Whiz Niraj
Haematinics: Iron Compounds
Comprehensive exam notes on Haematinics. Understand the role of Iron in blood, and the detailed preparation & assay of Ferrous Sulphate (*).
Definition: Haematinics are essential nutrients required for the normal formation of blood cells (Hemopoiesis). They are principally used for the prevention and treatment of Anemia (a condition where the blood has a lower than normal number of Red Blood Cells or hemoglobin).
The Role of Iron:
Iron is the most critical haematinic. About 70% of the body's iron is found in the red blood cells as a part of Hemoglobin. The iron atom (in its Ferrous state, Fe²⁺) sits at the center of the porphyrin ring of heme, where it reversibly binds to Oxygen (O₂) and transports it to tissues.
Clinical Alert: The Ferrous Rule
The human intestine primarily absorbs iron in its Ferrous state (Fe²⁺). The Ferric state (Fe³⁺) is poorly absorbed.
Pro Tip: Prescribing Vitamin C (Ascorbic Acid) along with iron supplements highly increases iron absorption. Vitamin C acts as a reducing agent, keeping the iron in the easily absorbable Ferrous (Fe²⁺) state. Conversely, Tannins present in Tea strongly decrease iron absorption.
Compounds marked with an asterisk (*) require a detailed study of their Preparation and Assay. Ferrous sulphate is the most commonly used, cheap, and highly effective haematinic.
Properties
- Formula: FeSO₄·7H₂O
- Synonym: Green Vitriol, Iron(II) sulphate.
- Appearance: Pale green, crystalline powder. It oxidizes in moist air to form brown basic ferric sulphate.
Preparation
It is prepared by reacting iron filings (scrap iron) with dilute sulphuric acid. Hydrogen gas is liberated during the process.
Assay of Ferrous Sulphate (Redox Titration)
The assay of Ferrous Sulphate is performed by an Oxidation-Reduction (Redox) Titration using Potassium Permanganate.
Principle of Assay:
Ferrous sulphate acts as a reducing agent. It is titrated against standard 0.1 N Potassium Permanganate (KMnO₄), which is a strong oxidizing agent.
The titration must be carried out in the presence of Dilute Sulphuric Acid (H₂SO₄). The acid prevents the oxidation of Fe²⁺ to Fe³⁺ by atmospheric oxygen and provides the necessary acidic medium for KMnO₄ to function.
Indicator: KMnO₄ acts as a Self-Indicator. The end point is indicated by the appearance of a permanent faint pink color.
Ferrous Gluconate is an organic iron salt used as a haematinic alternative to ferrous sulphate.
Properties
- Formula: C₁₂H₂₂FeO₁₄·2H₂O
- Appearance: Yellowish-gray or pale greenish-yellow fine powder with a slight odor of burnt sugar.
Why use it over Sulphate?
Ferrous sulphate often causes severe gastrointestinal irritation, leading to nausea, vomiting, and black stools. Ferrous gluconate is generally better tolerated by the stomach and causes less gastric irritation, making it preferable for sensitive patients.