BP106T Unit 3 – Precipitation, Complexometric & Redox Titrations
Unit 3 explores the physiological homeostasis of major bodily electrolytes (Sodium, Potassium, Calcium, Magnesium, Chloride, Bicarbonate, Phosphate), clinical electrolyte replacement therapy (Oral Rehydration Salts - WHO/IP formulation, Ringer's Solution, Normal Saline 0.9%), and inorganic Dental Products (Dentifrices/Abrasives, Anticaries fluoride mechanisms, Desensitizing agents, and Cements).
📋 Prescribed Syllabus Topics
📖 Detailed Lecture Notes & Solved Examples
11. Physiological Roles of Major Body Electrolytes & Fluid Balance
Dedicated Webpage➔Electrolytes are inorganic minerals that dissociate into electrically charged ions ($Cations^+$ and $Anions^-$) in aqueous biological fluids. Total Body Water accounts for ~60% of adult body weight, partitioned into Intracellular Fluid (ICF, 2/3 of total water) and Extracellular Fluid (ECF, 1/3 of total water: interstitial fluid and blood plasma). The principal Extracellular Cation is Sodium ($Na^+$, 135-145 mEq/L) which maintains osmotic pressure and fluid volume, paired with Extracellular Anions Chloride ($Cl^-$, 98-106 mEq/L) and Bicarbonate ($HCO_3^-$, 22-28 mEq/L). The principal Intracellular Cation is Potassium ($K^+$, 140-150 mEq/L inside cells; 3.5-5.0 mEq/L in plasma) essential for resting membrane potentials and cardiac rhythmicity, paired with Intracellular Anions Phosphate ($HPO_4^{2-}$) and proteins.Sodium (Na+) khoon aur cells ke bahar rehta hai aur BP maintain karta hai. Potassium (K+) cells ke andar rehta hai aur dil ki dhadkan (heart rhythm) control karta hai. Agar blood me potassium 5.5 se badh jaye (Hyperkalemia) ya 3.5 se kam ho jaye (Hypokalemia), toh dil ka daura padne ka khatra hota hai.
▶Clinical Consequences of Severe Electrolyte Imbalances
Pathophysiological emergencies resulting from electrolyte deviations.
| Electrolyte Ion | Primary Location | Normal Plasma Range | Core Physiological Function |
|---|---|---|---|
| Sodium ($Na^+$) | Extracellular Fluid (ECF) | 135 - 145 mEq/L | Primary determinant of ECF osmotic pressure, nerve action potentials |
| Potassium ($K^+$) | Intracellular Fluid (ICF) | 3.5 - 5.0 mEq/L | Resting membrane potential, cardiac repolarization, neuromusculature |
| Calcium ($Ca^{2+}$) | Bone (99%) / ECF (1%) | 8.5 - 10.5 mg/dL | Blood coagulation cascade, bone mineralization, muscle cross-bridge contraction |
| Magnesium ($Mg^{2+}$) | Intracellular / Bone | 1.5 - 2.5 mEq/L | Essential cofactor for over 300 ATP-dependent metabolic enzymes |
| Chloride ($Cl^-$) | Extracellular Fluid | 98 - 106 mEq/L | Maintains electroneutrality, gastric $HCl$ acid production |
| Bicarbonate ($HCO_3^-$) | Extracellular Fluid | 22 - 28 mEq/L | Primary physiological blood buffer neutralizing metabolic acids |
- •ECF Dominant Ions: $Na^+, Cl^-, HCO_3^-$ (Regulates arterial blood pressure and ECF volume).
- •ICF Dominant Ions: $K^+, Mg^{2+}, HPO_4^{2-}$ (Regulates cellular metabolism and intracellular enzyme systems).
- •Calcium Homeostasis: Maintained by Parathyroid Hormone (increases blood $Ca^{2+}$) and Calcitonin (decreases blood $Ca^{2+}$).
22. Electrolyte Replacement Therapy: ORS (WHO/IP Standard) & IV Fluids
Dedicated Webpage➔Acute dehydrating diarrhea (cholera, rotavirus gastroenteritis) causes life-threatening loss of water and electrolytes. Oral Rehydration Therapy (ORT) exploits the Sodium-Glucose Cotransport (SGLT-1) mechanism in small intestinal enterocytes: sodium is actively co-transported with glucose across mucosal brush borders even in severe cholera toxin diarrhea, dragging water molecules along by osmotic gradients. The World Health Organization (WHO) and Indian Pharmacopoeia (IP) prescribe the Reduced Osmolarity ORS Formulation.Severe dehydration me ORS diya jata hai. 1 Litre ORS me: NaCl (2.6g), KCl (1.5g), Trisodium citrate (2.9g), aur Glucose (13.5g) hota hai (Total 20.5g powder). Glucose aanto me Sodium aur Paani ko SGLT-1 pump ke zariye kheench leta hai jisse dehydration turant control hota hai.
▶Official WHO / IP Reduced Osmolarity ORS Formulation (Per 1.0 Liter)
Precise stoichiometric quantities and osmolarity breakdown.
- •Normal Saline (0.9% w/v NaCl): Isotonic with human plasma (Osmolarity ~308 mOsm/L; 154 mEq/L $Na^+$ + 154 mEq/L $Cl^-$).
- •Ringer's Injection: Contains $NaCl + KCl + CaCl_2$ matching plasma electrolyte profile.
- •Dextrose Normal Saline (DNS): 5% Dextrose + 0.9% NaCl (provides 170 kcal/L plus hydration).
- •Trisodium Citrate Advantage over Sodium Bicarbonate: Citrate is far more chemically stable in tropical packaging, preventing discoloration and caramelization of dextrose in humid storage.
33. Inorganic Dental Products: Dentifrices, Anticaries Fluorides & Cements
Dedicated Webpage➔Inorganic dental products maintain oral hygiene and treat dental diseases. Dentifrices are formulations (pastes/powders) used with a toothbrush to clean accessible tooth surfaces; they contain Abrasives/Polishing agents (Precipitated Calcium Carbonate, Dicalcium Phosphate Dihydrate) with controlled Mohs hardness (approx. 3.0) to remove dental plaque without scratching enamel (Mohs hardness ~5.0). Dental Caries (tooth decay) is caused by acidogenic oral bacteria (Streptococcus mutans) fermenting dietary carbohydrates to produce lactic acid, which dissolves dental hydroxyapatite [$Ca_{10}(PO_4)_6(OH)_2$]. Anticaries agents (Sodium Fluoride $NaF$, Stannous Fluoride $SnF_2$, Sodium Monofluorophosphate) convert hydroxyapatite into acid-resistant Fluorapatite.Daanto ke enamel (Hydroxyapatite) ko bacteria ka acid (pH < 5.5) gala kar cavity banata hai. Sodium Fluoride (NaF) enamel ke sath react karke use Fluorapatite me badal deta hai jo acid se nahi galta (pH < 4.5 par hi demineralize hota hai) aur daant me keeda lagne se bachata hai.
▶Mechanism of Fluoridation & Dental Remineralization
Chemical transformation of enamel.
- •Dental Fluorosis (Mottling of Enamel): Ingestion of excessive fluoride in drinking water (> 2 ppm) during tooth formation causes chalky-white patches or brown pitted stains.
- •Ideal Dentifrice Abrasiveness: Must clean pellicle and stain without abrading enamel or exposed root dentin.
- •Role of Stannous Fluoride ($SnF_2$): Provides both $F^-$ (anticaries) and $Sn^{2+}$ (antibacterial plaque inhibition).
- In a 10-mark question, write the complete WHO ORS composition (grams per liter and mEq/L osmolarity) and explain the physiological SGLT-1 cotransport mechanism.
- Explain the chemical mechanism of fluoride in preventing dental caries with balanced chemical equations.