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Introduction to Alkalinity Test and Standard Solutions

Introduction to Alkalinity Test and Standard Solutions. By Douglas Rittmann, Ph.D., P.E. Water/Wastewater Consultant Presented to CE 4153 On February 7, 2006. General Considerations. 1. Its capacity to neutralize acids or its buffering capacity. 2. 3 major classes of materials.

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Introduction to Alkalinity Test and Standard Solutions

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  1. Introduction to Alkalinity Testand Standard Solutions By Douglas Rittmann, Ph.D., P.E. Water/Wastewater Consultant Presented to CE 4153 On February 7, 2006

  2. General Considerations 1. Its capacity to neutralize acids or its buffering capacity. 2. 3 major classes of materials A. Bicarbonates, HCO3- - ≤ pH 8.3 B. Carbonates, CO3- - >pH 8.3 < pH 10 C. Hydroxide, OH- - > pH 10.0

  3. Sanitary Significance 1. Lime/Soda Ash Softening 2. Effects on Coagulant Dosing 3. Total Dissolved Solids compliance 4. Industrial Wastes Discharges 5. Calcium Carbonate Stability

  4. Method of Analysis 1. Phenolphthalein Alkalinity A. Phenolphthalein indicator B. pH 8.3 endpoint of titration C. Measures Carbonates and Hydroxide ions 2. Total Alkalinity A. Bromcresol green or Methyl Orange indicator B. pH 4.5 endpoint of titration C. Measures Bicarbonates

  5. Methods of Expressing 1. Phenolphthalein Alkalinity as CaCO3 P. Alk. = ml 0.02N sulfuric acid (1000/ml sample) = mg/L as CaCO3 2. Total Alkalinity as CaCO3 T. Alk. = ml 0.02N sulfuric acid X (1000/ml sample) = mg/L as CaCO3 3. Hydroxide, Carbonate, and Bicarbonate Alkalinity as CaCO3

  6. Alkalinity Relationships

  7. Standard Solutions • General Considerations 1. Saves Time in calculating results 2. Selection of Proper Normality is convenient * 1 mg/ml or 1000mg solution * 1/eq.wt., example: Alkalinity as CaCO3 = 0.02 N 3. Preparation of Solution of Proper Normality * Material of Known purity is weighed & transferred to volumetric flask * Purchase Solutions of known Normality

  8. Preparation of 1N Acid Solution * Sulfuric acid used for Alkalinity Test 1 GMW = 98 g pure H2SO4 = 2.016 g H+ 1 GMW/2 = 49 g pure H2SO4 = 1.008 g H+ Acid is 96% pure, then 49/0.96 = 51 g = 1.008 g H+ Make 5% stronger = 51 X 1.05 = 53.5 g Procedure: Weigh about 53g of conc. acid into a small beaker on Trip balance. Place 500 ml of distilled water in 1-liter graduated cylinder And add the acid to it. Rinse the contents of the beaker into the cylinder With distilled water, and add water to the 1-liter mark. Mix by pouring Back and forth from the cylinder into a large beaker. Cool to room temp.

  9. Primary Standard * Sodium Carbonate is a convenient primary standard MW = 106 of Na2CO3 1EW or 1N = 53g/L when reacting with H2SO4 to pH 4.5, T. Alk endpoint Preparation of 0.02 N Acid or N/50 can be made from 1N based on ml X N = ml X N Example: ml X 1.0 = 1000 X 0.02 ml = 20

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