CHAPTER Ⅰ THE SILICA-WATER SYSTEM 3
1．Silica—General Occurrence 3
2．Solubility of Silica 4
2a．Various Modifications of Silica 4
2b．Relation between Particle Size and Solubility 8
2c．The Nature of Soluble Silica;Effect of pH 11
3．Rate of Dissolution of Silica 13
3a．Mechanism of Dissolution 13
3b．Effect of Particle Size 14
3c．Effect of Impurities 14
4．Deposition of Silica from Solution 15
References 16
CHAPTER Ⅱ THE SOLUBLE SILICATES 18
1．Introduction 18
2．Formation of Silicate Ions in Aqueous Solution 18
3．Soluble Silicate Glasses 19
4．Polymerization-Depolymerization Phenomena in Aqueous Silicate Solutions 20
4a．Formation of Polysilicate Ions 21
4b．Structure of Polysilicate Ions 24
4c．Equilibrium:Polymerization vs．Depolymerization 24
4d．Molecular Weight of Sodium Silicate in Aqueous Solution 26
4e．Polymerization Due to Added Salts 28
5．Crystalline Alkali Metal Silicates 28
5a．Orthosilicates 28
5b．Metasilicates 29
5c．Disilicates 30
5d．Polysilicates 30
6．Other Soluble Silicates 30
6a．Quaternary Ammonium Silicates 30
6b．Silicates of Werner Complex Bases 31
6c．Silicon in Complex Anions 31
7．Effect of Electrolytes and Organic Solvents on Soluble Silicates 31
7a．Effect of Alkali Metal Salts 31
7b．Water-miscible Organic Solvents 32
References 32
CHAPTER Ⅲ THE CHEMISTRY OF SILICIC ACID 34
1．Preparation of Monosilicic Acid 34
1a．Solution Saturated with Respect to Amorphous Silica 34
1b．Hydrolysis of Monomeric Silicon Compounds 35
1c．Reaction of Monomeric Metal Silicates with Acids 35
2．Polymerization of Silicic Acid 36
2a．Mechanism of Formation of Siloxane Bonds 36
2b．Formation of Colloidal Silica and Polysilicic Acids 38
2c．Polymerization of Silicic Acid in Acidic vs．Basic Solution 41
2d．Formation of Gel 43
2e．Structure of Primary Particles in Gel 44
2f．General Summary of Polymerization and Aggregation 44
3．Factors Affecting Rate of Polymerization of Silicic Acid to Form Gel 45
3a．Effects of pH and Impurities 45
3b．Mechanism of Catalyzed Reaction in Acidic Solution 48
3c．Concentration of Silica 54
3d．Effect of Water-miscible Organic Solvents 55
4．Properties of Soluble Polysilicic Acids 55
4a．Physical Characteristics 55
4b．Acid Strength 56
4e．Heat of Polymerization 57
5．Reactions of Polysilicic Acid 58
5a．Complexes Formed with Polar Organic Compounds 58
5b．Combination with Organic Polymers 67
5c．Reaction with Metal Ions 68
References 69
CHAPTER Ⅳ ESTERS OF SILICIC AND POLYSILICIC ACID 72
1．Introduction 72
2．Hydrolysis of Esters to Silicic and Polysilicic Acid 73
3．Practical Aspects of Silicic Esters 75
4．Esters of Polysilicic Acid Prepared by the Hydrolysis and Con-densation of Alkoxychlorosilanes 77
5．Esterification of Polysilicic Acid 80
6．Polymeric Silicic Esters Linked through Carbon 84
7．Summary of Siloxane Polymer Structures 84
References 85
CHAPTER Ⅴ COLLOIDAL SILICA 87
1．Definition 87
2．Polysilicic Acids and Colloidal Silica 87
3．Recent Developments 89
4．Methods of Preparing Aqueous Sols 90
4a．Dialysis 90
4b．Electrodialysis 90
4c．Dissolution of Elemental Silicon 90
4d．Sols by Reaction of Acid with Sodium Silicate 91
4e．Peptizing Gels at Elevated Temperature 92
4f．Ion Exchange 93
5．Nature of the Particles 95
5a．Amorphous Nature 95
5b．Degree of Aggregation;Effect on Viscosity 96
5c．Degree of Hydration 98
6．Particle Size and Shape 100
6a．Measurement by the Electron Microscope 101
6b．Methods of Determining Specific Surface Area 103
6c．Comparison of Methods 105
7．Ionic Charge on the Particles 106
7a．Effect of pH 106
7b．Effect of Electrolytes 108
7c．Effect of Organic Solvents 110
7d．Types of Counter Ions 110
7e．Water-soluble Colloidal Silica Powder 112
8．Stability of Colloidal Silica—Gelling Mechanism 113
9．Products and Applications 114
9a．Commercial Products 114
9b．Uses of Aqueous Sols 114
10．Organosols 120
10a．Preparation 120
10b．Uses 121
References 122
CHAPTER Ⅵ AMORPHOUS SILICA GELS AND POWDERS 127
1．Introduction 127
2．Structure of Silica Gel 129
2a．Size and Shape of Primary Particles 130
2b．Density of Packing of Primary Particles 130
2c．Nature of the Bond between Particles 132
2d．Range of Structure 133
3．Characterization of Silica Gels and Powders 134
3a．Size and Shape of Primary Particles;Specific Surface Area 134
3b．Density of Packing of Primary Particles;Porosity 135
3c．Coalescence;Interparticle Bonding 137
3d．Other Methods 137
4．Methods of Preparing and Drying Xerogels 137
4a．Preparation from Soluble Silicates and Acids 139
4b．Gels from Colloidal Silica 140
4c．Dehydration of Silica Gels 140
5．Adsorptive Properties of Silica Gels 144
5a．Capillary Condensation and Monolayer Adsorption 144
5b．Pore Volumes;Micropores and Macropores 145
5c．Adsorption Hysteresis 148
5d．Adsorbates 148
5e．Specific Adsorbents 150
6．Miscellaneous Gel Structures 152
6a．Aerogels 152
6b．Definite Silica Hydrates 154
6c．Porous Silica Gels from Glasses 156
7．Fine Silica Powders 157
7a．Particle Size and Aggregation 157
7b．Preparation by Precipitation from Aqueous Solution 159
7c．Condensation from SiO2 Vapor 168
8．Hydrophobic Silica Gels and Powders 169
9．Products and Uses 174
References 175
CHAPTER Ⅶ COLLOIDAL SILICATES 181
1．Introduction 181
2．Amorphous Insoluble Silicates 181
2a．Formation from Soluble Silicates and Metal Salts 181
2b．Aluminosilicates 184
3．Microporous Crystalline Zeolites 186
3a．Adsorption of Gases 186
3b．Cation Exchange in Microporous Silicates 189
4．Sheetlike Crystalline Silicates of Colloidal Thickness 190
4a．The Montmorillonite Minerals 191
4b．The Mica Group;Mechanically Dispersible Colloids 198
4c．The Kaolin Group 202
5．Rodlike and Fiberlike Crystalline Silicates of Colloidal Thickness 206
5a．Tubular Fibers 206
5b．Lathlike Fibers 212
5c．Other Fibrous Minerals 215
6．Plasticity of Clays and Soils 217
6a．Plasticity 217
6b．Soil Conditioning 219
7．Organic Modifications of Colloidal Silicates 220
7a．Nonionic Polar Organic Compounds 221
7b．Cationic Organic Compounds 223
7c．Anionic Organic Compounds 226
7d．Other Procedures 227
References 228
CHAPTER Ⅷ SURFACE CHEMISTRY OF SILICA AND SILICATES 233
1．Introduction 233
2．The Silanol Surface of Amorphous Silica 234
2a．Composition and Dehydration 234
2b．Effect of Dehydration of the Surface on Adsorption of Polar Molecules 238
2c．Heat of Wetting by Water 240
2d．The Geometry of the Silanol Surface;Hydroxyl Groups per Square Millimicron 242
3．Adsorption of Inorganic Ions 247
3a．Adsorption of Hydroxyl Ions 247
3b．Adsorption of Metal Ions 249
3c．Polarization of Metal Ions 250
4．The Adsorption of Nonionic Organic Compounds 251
4a．Adsorption of Organic Compounds from the Gas Phase 253
4b．Adsorption from Solution 254
4c．Organic-coated Aerogel 254
5．Chemically Bound Coatings 255
5a．Halides 255
5b．Adsorption of Organic Cations 255
5c．Adsorption of Soaps and Complexes of Aliphatic Acids 256
5d．Organosilicon Compounds 257
5e．Reaction of Alcohols with the Silica Surface;Estersils 257
6．The Surface of Quartz 258
7．The Surface of Crystalline Aluminosilicates 259
8．The Surface of Amorphous Aluminosilicate Cracking Catalysts 261
8a．Acidity and Catalytic Activity 262
8b．Nature of the Acid Sites 263
8c．Lability of the Aluminosilicate Structure 265
8d．Water Content and Catalytic Activity 266
8e．Poisoning the Surface 267
9．Sintering of Silica Gels 269
References 272
CHAPTER Ⅸ SILICA IN LIVING ORGANISMS 276
1．Introduction 276
1a．Silicates and the Origin of Life 276
1b．Role of Organic Matter in the Decomposition of Mineral Silicates 278
1c．Detection of Silica in Organic Matter 279
2．Occurrence in Lower Organisms 280
3．Occurrence in Plants 282
3a．Silicon Requirement in Plants 282
3b．Effect on Soil Fertility 283
3c．Effect on Resistance of Plants to Disease 284
3d．Occurrence of Silica in Plant Tissues 286
3e．Mechanism of Entry of Silica into Plants and the Com-pounds Formed 289
3f．Silicification of Wood and Plant Tissues 291
4．Occurrence of Silica in Animals 293
4a．Significance 293
4b．Quantities Found 294
4c．Formation of Organic-Silica Complexes 294
5．Silica Gel as a Culture Medium 296
6．Conclusion 296
References 297
AUTHOR INDEX 301
SUBJECT INDEX 310