《THE COLLOID CHEMISTRY OF SILICA AND SILICATES》

CHAPTER ⅠTHE SILICA-WATER SYSTEM3

1．Silica—General Occurrence3

2．Solubility of Silica4

2a．Various Modifications of Silica4

2b．Relation between Particle Size and Solubility8

2c．The Nature of Soluble Silica;Effect of pH11

3．Rate of Dissolution of Silica13

3a．Mechanism of Dissolution13

3b．Effect of Particle Size14

3c．Effect of Impurities14

4．Deposition of Silica from Solution15

References16

CHAPTER ⅡTHE SOLUBLE SILICATES18

1．Introduction18

2．Formation of Silicate Ions in Aqueous Solution18

3．Soluble Silicate Glasses19

4．Polymerization-Depolymerization Phenomena in Aqueous Silicate Solutions20

4a．Formation of Polysilicate Ions21

4b．Structure of Polysilicate Ions24

4c．Equilibrium:Polymerization vs．Depolymerization24

4d．Molecular Weight of Sodium Silicate in Aqueous Solution26

4e．Polymerization Due to Added Salts28

5．Crystalline Alkali Metal Silicates28

5a．Orthosilicates28

5b．Metasilicates29

5c．Disilicates30

5d．Polysilicates30

6．Other Soluble Silicates30

6a．Quaternary Ammonium Silicates30

6b．Silicates of Werner Complex Bases31

6c．Silicon in Complex Anions31

7．Effect of Electrolytes and Organic Solvents on Soluble Silicates31

7a．Effect of Alkali Metal Salts31

7b．Water-miscible Organic Solvents32

References32

CHAPTER ⅢTHE CHEMISTRY OF SILICIC ACID34

1．Preparation of Monosilicic Acid34

1a．Solution Saturated with Respect to Amorphous Silica34

1b．Hydrolysis of Monomeric Silicon Compounds35

1c．Reaction of Monomeric Metal Silicates with Acids35

2．Polymerization of Silicic Acid36

2a．Mechanism of Formation of Siloxane Bonds36

2b．Formation of Colloidal Silica and Polysilicic Acids38

2c．Polymerization of Silicic Acid in Acidic vs．Basic Solution41

2d．Formation of Gel43

2e．Structure of Primary Particles in Gel44

2f．General Summary of Polymerization and Aggregation44

3．Factors Affecting Rate of Polymerization of Silicic Acid to Form Gel45

3a．Effects of pH and Impurities45

3b．Mechanism of Catalyzed Reaction in Acidic Solution48

3c．Concentration of Silica54

3d．Effect of Water-miscible Organic Solvents55

4．Properties of Soluble Polysilicic Acids55

4a．Physical Characteristics55

4b．Acid Strength56

4e．Heat of Polymerization57

5．Reactions of Polysilicic Acid58

5a．Complexes Formed with Polar Organic Compounds58

5b．Combination with Organic Polymers67

5c．Reaction with Metal Ions68

References69

CHAPTER ⅣESTERS OF SILICIC AND POLYSILICIC ACID72

1．Introduction72

2．Hydrolysis of Esters to Silicic and Polysilicic Acid73

3．Practical Aspects of Silicic Esters75

4．Esters of Polysilicic Acid Prepared by the Hydrolysis and Con-densation of Alkoxychlorosilanes77

5．Esterification of Polysilicic Acid80

6．Polymeric Silicic Esters Linked through Carbon84

7．Summary of Siloxane Polymer Structures84

References85

CHAPTER ⅤCOLLOIDAL SILICA87

1．Definition87

2．Polysilicic Acids and Colloidal Silica87

3．Recent Developments89

4．Methods of Preparing Aqueous Sols90

4a．Dialysis90

4b．Electrodialysis90

4c．Dissolution of Elemental Silicon90

4d．Sols by Reaction of Acid with Sodium Silicate91

4e．Peptizing Gels at Elevated Temperature92

4f．Ion Exchange93

5．Nature of the Particles95

5a．Amorphous Nature95

5b．Degree of Aggregation;Effect on Viscosity96

5c．Degree of Hydration98

6．Particle Size and Shape100

6a．Measurement by the Electron Microscope101

6b．Methods of Determining Specific Surface Area103

6c．Comparison of Methods105

7．Ionic Charge on the Particles106

7a．Effect of pH106

7b．Effect of Electrolytes108

7c．Effect of Organic Solvents110

7d．Types of Counter Ions110

7e．Water-soluble Colloidal Silica Powder112

8．Stability of Colloidal Silica—Gelling Mechanism113

9．Products and Applications114

9a．Commercial Products114

9b．Uses of Aqueous Sols114

10．Organosols120

10a．Preparation120

10b．Uses121

References122

CHAPTER ⅥAMORPHOUS SILICA GELS AND POWDERS127

1．Introduction127

2．Structure of Silica Gel129

2a．Size and Shape of Primary Particles130

2b．Density of Packing of Primary Particles130

2c．Nature of the Bond between Particles132

2d．Range of Structure133

3．Characterization of Silica Gels and Powders134

3a．Size and Shape of Primary Particles;Specific Surface Area134

3b．Density of Packing of Primary Particles;Porosity135

3c．Coalescence;Interparticle Bonding137

3d．Other Methods137

4．Methods of Preparing and Drying Xerogels137

4a．Preparation from Soluble Silicates and Acids139

4b．Gels from Colloidal Silica140

4c．Dehydration of Silica Gels140

5．Adsorptive Properties of Silica Gels144

5a．Capillary Condensation and Monolayer Adsorption144

5b．Pore Volumes;Micropores and Macropores145

5c．Adsorption Hysteresis148

5d．Adsorbates148

5e．Specific Adsorbents150

6．Miscellaneous Gel Structures152

6a．Aerogels152

6b．Definite Silica Hydrates154

6c．Porous Silica Gels from Glasses156

7．Fine Silica Powders157

7a．Particle Size and Aggregation157

7b．Preparation by Precipitation from Aqueous Solution159

7c．Condensation from SiO2 Vapor168

8．Hydrophobic Silica Gels and Powders169

9．Products and Uses174

References175

CHAPTER ⅦCOLLOIDAL SILICATES181

1．Introduction181

2．Amorphous Insoluble Silicates181

2a．Formation from Soluble Silicates and Metal Salts181

2b．Aluminosilicates184

3．Microporous Crystalline Zeolites186

3a．Adsorption of Gases186

3b．Cation Exchange in Microporous Silicates189

4．Sheetlike Crystalline Silicates of Colloidal Thickness190

4a．The Montmorillonite Minerals191

4b．The Mica Group;Mechanically Dispersible Colloids198

4c．The Kaolin Group202

5．Rodlike and Fiberlike Crystalline Silicates of Colloidal Thickness206

5a．Tubular Fibers206

5b．Lathlike Fibers212

5c．Other Fibrous Minerals215

6．Plasticity of Clays and Soils217

6a．Plasticity217

6b．Soil Conditioning219

7．Organic Modifications of Colloidal Silicates220

7a．Nonionic Polar Organic Compounds221

7b．Cationic Organic Compounds223

7c．Anionic Organic Compounds226

7d．Other Procedures227

References228

CHAPTER ⅧSURFACE CHEMISTRY OF SILICA AND SILICATES233

1．Introduction233

2．The Silanol Surface of Amorphous Silica234

2a．Composition and Dehydration234

2b．Effect of Dehydration of the Surface on Adsorption of Polar Molecules238

2c．Heat of Wetting by Water240

2d．The Geometry of the Silanol Surface;Hydroxyl Groups per Square Millimicron242

3．Adsorption of Inorganic Ions247

3a．Adsorption of Hydroxyl Ions247

3b．Adsorption of Metal Ions249

3c．Polarization of Metal Ions250

4．The Adsorption of Nonionic Organic Compounds251

4a．Adsorption of Organic Compounds from the Gas Phase253

4b．Adsorption from Solution254

4c．Organic-coated Aerogel254

5．Chemically Bound Coatings255

5a．Halides255

5b．Adsorption of Organic Cations255

5c．Adsorption of Soaps and Complexes of Aliphatic Acids256

5d．Organosilicon Compounds257

5e．Reaction of Alcohols with the Silica Surface;Estersils257

6．The Surface of Quartz258

7．The Surface of Crystalline Aluminosilicates259

8．The Surface of Amorphous Aluminosilicate Cracking Catalysts261

8a．Acidity and Catalytic Activity262

8b．Nature of the Acid Sites263

8c．Lability of the Aluminosilicate Structure265

8d．Water Content and Catalytic Activity266

8e．Poisoning the Surface267

9．Sintering of Silica Gels269

References272

CHAPTER ⅨSILICA IN LIVING ORGANISMS276

1．Introduction276

1a．Silicates and the Origin of Life276

1b．Role of Organic Matter in the Decomposition of Mineral Silicates278

1c．Detection of Silica in Organic Matter279

2．Occurrence in Lower Organisms280

3．Occurrence in Plants282

3a．Silicon Requirement in Plants282

3b．Effect on Soil Fertility283

3c．Effect on Resistance of Plants to Disease284

3d．Occurrence of Silica in Plant Tissues286

3e．Mechanism of Entry of Silica into Plants and the Com-pounds Formed289

3f．Silicification of Wood and Plant Tissues291

4．Occurrence of Silica in Animals293

4a．Significance293

4b．Quantities Found294

4c．Formation of Organic-Silica Complexes294

5．Silica Gel as a Culture Medium296

6．Conclusion296

References297

AUTHOR INDEX301

SUBJECT INDEX310