SOLID SOLUTIONS. MIXED CRYSTALS 175 General, 175. Solution of gases in solids, 176. Palladium and hydrogen, 178. Solutions of solids in solids. Mixed crystals, 180. Formation of mixed crystals of isomorphous substances, 182. I. The two components can form an unbroken series of mixed crystals. (_a_) _The freezing points of all mixtures lie between the freezing points of the pure components._ Examples, 183. Melting-point curve, 183. (_b_) _The freezing-point curve passes through a maximum._ Example, 186. (_c_) _The freezing-point curve passes through a minimum._ Example, 188. Fractional {xiv} crystallization of mixed crystals, 188. II. The two components do not form a continuous series of mixed crystals. (_a_) _The freezing-point curve exhibits a transition point_, 190. Example, 190. (_b_) _The freezing-point curve exhibits a eutectic point_, 191. Examples, 192. Changes in mixed crystals with the temperature, 192. CHAPTER XI EQUILIBRIUM BETWEEN DYNAMIC ISOMERIDES 195 Temperature-concentration diagram, 196. Transformation of the unstable into the stable form, 201. Examples, 203. _Benzaldoximes_, 203. _Acetaldehyde and paraldehyde_, 204. CHAPTER XII SUMMARY.--APPLICATION OF THE PHASE RULE TO THE STUDY OF SYSTEMS OF TWO COMPONENTS 207 Summary of the different systems of two components, 208. (1) _Organic compounds_, 212. (2) _Optically active substances_, 213. Examples, 216. Transformations, 217. (3) _Alloys_, 220. Iron--carbon alloys, 223. Determination of the composition of compounds without analysis, 228. Formation of minerals, 232. CHAPTER XIII SYSTEMS OF THREE COMPONENTS 234 General, 234. Graphic representation, 235. CHAPTER XIV SOLUTIONS OF LIQUIDS IN LIQUIDS 240 1. _The three components form only one pair of partially miscible liquids_, 240. Retrograde solubility, 245. The influence of temperature, 247. 2. _The three components can form two pairs of partially miscible liquids_, 249. 3. _The three components form three pairs of partially miscible liquids_, 251. CHAPTER XV PRESENCE OF SOLID PHASES 253 A. The ternary eutectic point, 253. Formation of compounds, 255. B. Equilibria at higher temperatures. Formation of double salts, 258. Transition point, 258. Vapour pressure. {xv} Quintuple point, 261. Solubility curves at the transition point, 264. Decomposition of the double salt by water, 267. Transition interval, 270. Summary, 271. CHAPTER XVI ISOTHERMAL CURVES AND THE SPACE MODEL 272