The solubility of gases and liquids in liquids is of great importance in large areas of operations based on chemical concepts. Phenomena have appeared to be so varied that even experts have from time to time remarked on the difficulty of seeing a consistent pattern. Now for the first time the essential pattern of all known gas solubility data is set out in a graphic form for all to see. The continuous merging of the gas-liquid systems and the liquid-liquid systems is also illustrated. The pattern opens the way to rational predictions. The new data given for the lower alkanes and alkenes, the three methylamines, ammonia, bromomethane, and chloroethane, together with my previously reported data on hydrogen sulfide, dimethyl ether, chloromethane, and sulfur dioxide, have been obtained by a bubbler-manometer procedure which is fully described. Not only are these data of significance in many chemical processes, but they have also been vital to the development of the overall essential pattern covering all gases. The book is for chemists, chemical engineers, biotechnologists, certain physi cists, and teachers and students in these disciplines. It is a book for all those who are concerned with the use and inculcation of the fundamental, even rudimentary, principles of chemistry.