CHAPTER XI

ON THE DEVELOPMENT OF PHYSICAL CHEMISTRY SINCE 1850 171 Molecular volumes of liquids. Nature of solution. Van ’t Hoff’s application of the gas laws to phenomena of solution. Osmosis and osmotic pressure. Traube. Pfeffer. Semi-permeable membranes. Measurement of osmotic pressure. Arrhenius. Doctrine of ionisation. Its applicability to the explanation of chemical phenomena. Thermo-chemistry. Mass action. Nature of reversible reactions. Thermal and Electrolytic dissociation. Relation between chemical nature and opticity, magnetic rotation and viscosity. Theory of phases. Catalysis. Enzyme action. Relations between valency and volume. Photochemistry.

BIBLIOGRAPHY 187

INDEX 191

ILLUSTRATIONS

PAGE JUSTUS VON LIEBIG _Frontispiece_

JEAN BAPTISTE ANDRÉ DUMAS 9

THOMAS GRAHAM 13 From a painting by G. F. Watts, R.A., in the possession of the Royal Society

ALEXANDER WILLIAM WILLIAMSON 15

BUNSEN, KIRCHHOFF, AND ROSCOE 19

SIR WILLIAM RAMSAY 48

MARIE CURIE (_née_ SKLODOWSKA) 56

STANISLAO CANNIZZARO 65

SIR JAMES DEWAR 98

DMITRI IVANOWITSCH MENDELÉEFF 110

AUGUST KEKULÉ VON STRADONITZ 126

JACOBUS HENRICUS VAN ’T HOFF 142

EMIL FISCHER 166

SVANTE AUGUST ARRHENIUS 180

HISTORY OF CHEMISTRY